Papers - YOKOTA Kenji
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Involvement of iturin and surfactin in inhibition of a post-harvest fungal pathogen on green bell pepper Reviewed International coauthorship International journal
Yuliar, Shun Tomita, Hinako Hishinuma, Kenji Yokota
Journal of Plant Protection Research 2025.03
Authorship：Last author Language：English Publishing type：Research paper (scientific journal)
This study aimed to investigate the potential of plant-associated bacteria as bio-control agents for the green bell pepper rot lesion caused by Colletotrichum scovillei 244830. A total of 378 bacteria strains isolated from stems and leaves of healthy red chili and tomato were tested for their antagonistic potential. Isolate TS001 associated with tomato stems was identified as Bacillus spp. It was found that TS001 showed remarkable inhibition to C. scovillei 244830 in in vitro and in vivo tests. TS001 significantly reduced rot lesions (P<0.05) of fresh green bell pepper fruits by 71.43%. Furthermore, the result of the LC-ESI-MS/MS showed that the culture broth of the strain Bacillus sp. TS001 contained iturin and surfactin homolog in No. 3S medium. TS001 exhibited the strongest antagonistic activity that effectively suppressed C. scovillei 244830 rot lesion. -
Characterization of NRPS operon homologue for surfactin synthesis distributed in Bacillus spp. Reviewed International journal
Kojiro Ito, Mana Adachi, Minenosuke Matsutani, Ryota Kataoka, Gen Enomoto, Akinobu Kajikawa, Kenji Yokota
Archives of Microbiology 2025
Authorship：Last author, Corresponding author Language：English Publishing type：Research paper (scientific journal)
Surfactin is a cyclic lipopeptide consists of a b-hydroxy fatty acid and a heptapeptide derived from Bacillus spp. The heptapeptide moiety of surfactin is synthesized by non-ribosomal peptide synthetases, and a variety of surfactin congeners which are varied by substitution of amino acid in the heptapeptide have been identified so far. Surfactin A, B and C are surfactin congeners which are substituted of Leu7 of surfactin A with Val for surfactin B or Ile for surfactin C. The operon encoding non-ribosomal peptide synthetases for surfactin A had been identified in B. subtilis JH 642. Here, we report that novel operons encoding non-ribosomal peptide synthetases for surfactin A and C biosynthesis, respectively.
The srfA operon for surfactin A biosynthesis in B. subtilis composed by 4-ORFs, srfAABCD. The novel operon for surfactin A biosynthesis was distinct from the srfA operon in B. subtilis JCM 1465 with 68.5, 69.2, 84.5 and 66.9 % homology of ORFs, respectively. The novel surfactin C showed 68.7, 69.3, 64.5 and 67.2 % homology with srfA operon in B. subtilis JCM 1465, respectively, and the adenylation domain to select Ile7 in surfactin C was identified by a domain substitution in srfA operon in a surfactin A-producing strain. Average Nucleotide Identity of genomic sequence of tested strains clearly showed that the novel operons for surfactin A and C biosynthesis are distributed in B. velezensis and B. amyloliquefaciens, respectively. Our results indicate surfactin congener production was strictly related to the species level of Bacillus and srf operon was suggested to be distributed by species. -
TAMAKI Mizuna, CHIKU Tsutomu, SUZUKI Shunya, MISAKI Aya, FUNAKUBO Asuka, MATSUSHIMA Yoshitaka, YOKOTA Kenji, IGIMI Shizunobu, KAJIKAWA Akinobu
Bioscience of Microbiota, Food and Health 44 ( 1 ) 70 - 79 2024.09
Language：English Publisher：BMFH Press
Although the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas system has been extensively developed since its discovery for eukaryotic and prokaryotic genome editing and other genetic manipulations, there are still areas warranting improvement, especially regarding bacteria. In this study, BRD0539, a small-molecule inhibitor of Streptococcus pyogenes Cas9 (SpCas9), was used to suppress the activity of the nuclease during genetic modification of Lacticaseibacillus paracasei, as well as to regulate CRISPR interference (CRISPRi). First, we developed and validated a CRISPR-SpCas9 system targeting the sirA gene of L. paracasei. Then BRD0539 was used for CRISPR-dependent DNA cleavage in vivo. Our results suggested that the inhibitor worked partially in both Escherichia coli and L. paracasei. Next, we designed a CRISPRi system in a L. paracasei strain by inserting an inactive SpCas9 gene into the chromosome and introducing a plasmid encoding for a single guide RNA (sgRNA) targeting the sirA gene. Expression of sirA was successfully inhibited in the recombinant strains, and CRISPRi was abolished in an inhibitor-dependent manner. Our findings may help expand the CRISPR toolbox for research on lactic acid bacteria and other microbes.
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Heat-stable spores of carotenoid-producing Bacillus marisflavi and non-pigmented Bacillus subtilis cooperatively promote growth, quality, and gut microbiota of white-leg shrimp Reviewed International coauthorship International journal
T.T. Nguyen, A.T.P. Bui, N.T.H. Le, H.T. N. Vo, A.H. Nguyen, T.D. Pham, T. Hara, K. Yokota, M. Matsutani, Y. Takatsuka, A.T.V. Nguyen
Beneficial Microbes 2023.11
Language：English Publishing type：Research paper (scientific journal)
We evaluated the benefits of heat-stable carotenoid-producing Bacillus marisflavi SH8 spores individually and in combination with non-pigmented Bacillus subtilis SH23 spores on growth, colour change, nutritional content, innate immunity, and gut microbiota of white-leg shrimp. White-leg shrimp (Litopenaeus vannamei; n = 30 per tank; 2 tanks per group) were provided feed without (control group) or with SH8, SH23, or mixed spores (total, 1×106 cfu/g pellet) for 28 d. The SH8 and SH8-23 combination groups had significantly higher specific growth rates (9.6 and 11.0%), improved red-colour score (4 scores), astaxanthin concentration (1.8- and 2.3-fold), lipid contents (30 and 50%), and superoxidase dismutase activity (8.5 and 12.3%) than that of the control group. Analysis of shrimp’s gut microbiome using 16S rRNA metagenome sequencing revealed increased abundance of four useful species and reduced abundance of four harmful species in the combination group than in the control group. Heat-stable Bacillus spore combination improved growth parameters, nutrient content, red-colour score, live counts, and abundance of useful bacteria in the gut of L. vannamei. This is the first study to show the benefits of combining highly heat-stable pigmented and non-pigmented Bacillus spores and their possible mechanisms in a shrimp model.
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Negative chemotaxis of Ligilactobacillus agilis BKN88 against gut-derived substances Reviewed International journal
Shunya Suzuki, Kenji Yokota, Shizunobu Igimi, Akinobu Kajikawa
Scientific Reports 13 2023.09
Language：English Publishing type：Research paper (scientific journal)
Ligilactobacillus agilis is a motile lactic acid bacterium found in the gastrointestinal tracts of animals. The findings of our previous study suggest that the motility of L. agilis BKN88 enables gut colonization in murine models. However, the chemotactic abilities of motile lactobacilli remain unknown. This study aimed to identify the gut-derived chemoeffectors and their corresponding chemoreceptors in L. agilis BKN88. Chemotaxis assays with chemotactic and non-chemotactic (ΔcheA) L. agilis strains revealed that low pH, organic acids, and bile salts served as repellents. L. agilis BKN88 was more sensitive to bile and acid than the gut-derived non-motile lactobacilli, implying that L. agilis might utilize motility and chemotaxis instead of exhibiting stress tolerance/resistance. L. agilis BKN88 contains five putative chemoreceptor genes (mcp1–mcp5). Chemotaxis assays using a series of chemoreceptor mutants revealed that each of the five chemoreceptors could sense multiple chemoeffectors and that these chemoreceptors were functionally redundant. Mcp2 and Mcp3 sensed all tested chemoeffectors. This study provides further insights into the interactions between chemoreceptors and ligands of motile lactobacilli and the unique ecological and evolutionary features of motile lactobacilli, which may be distinct from those of non-motile lactobacilli.
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エノキタケ黒腐細菌病の生物的防除のためのPseudomonas sp. BM2-6株の効果的な処理方法 Reviewed
横山遼人, 鈴木千尋, 服部雄斗, 富田 駿, 横田健治, キムオッキョン, 岩波 徹, 篠原弘亮
東京農業大学農学集報 68 ( 1 ) 13 - 22 2023.06
Language：Japanese Publishing type：Research paper (scientific journal)
著者ら（2018）はエノキタケ黒腐細菌病（病原：Pseudomonas tolaasii）に対し発病抑制効果のある P. sp. BM2-6 株を見出した。本研究では BM2-6 株の有効な処理方法を検討し，発病抑制機構を考察した。 BM2-6 株細菌懸濁液のエノキタケ（Flammulina velutipes）幼子実体への噴霧処理または菌掻き時処理した ところ，防除価はいずれも高く，約 109 cfu/ml において 99.6，98.4 であった。約 106 cfu/ml において 83.3， 90.3 であった。約 1010 cfu/mL または約 106 cfu/mL の BM2-6 株細菌懸濁液処理および約 105 cfu/mL の P. tolaasii 814 株細菌懸濁液接種におけるエノキタケ菌床または子実体での両菌の各細菌数を調査した。これ らエノキタケに発病は認められず，菌床における BM2-6 株は各処理ともに約 108 cfu/g, P. tolaasii 814 株は それぞれ約 106 cfu/g, 約 107 cfu/g 定着していた。子実体における両菌は各処理ともそれぞれ約 107 cfu/g, 約 108 cfu/g 定着していた。BM2-6 株はトラシン解毒能も持たないことから，液体培地中で両菌を混合培養し， 両細菌数および腐敗の主因であるトラシンⅠの量を測定した。P. tolaasii 814 株の単独培養時，約 1010 cfu/ mL を超えるとトラシンⅠが最大 45.9 µg/mL 検出された。一方，混合培養では，両菌ともに約 1010 cfu/mL まで増殖したがトラシンⅠは非検出であったことから，BM2-6 株の発病抑制機構は P. tolaasii 814 株のトラ シン産生抑制であると判断した。以上，BM2-6 株は菌掻き時処理により本病を効果的に防除でき，P. tolaasii のトラシン産生を抑制することによって発病を抑制した。
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Strategies for Biological Control of Brown Blotch Disease
TOMITA Shun, SHINOHARA Hirosuke, YOKOTA Kenji
KAGAKU TO SEIBUTSU 61 ( 3 ) 116 - 124 2023.03
Language：Japanese Publisher：Japan Society for Bioscience, Biotechnology, and Agrochemistry
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Bacillus属細菌を用いた植物病害生物防除における環状リポペプチドの機能
横田 健治
日本農薬学会誌 47 ( 2 ) 124 - 125 2022.08
Language：Japanese Publisher：日本農薬学会
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Insights on suppression of bacterial leaf spot by Bacillus cyclic lipopeptides via induced resistance in Arabidopsis thaliana Reviewed
Carla Suzuki Altrão, Mana Kaneko, Shigeaki Shiina, Akinobu Kajikawa, Hirosuke Shinohara, Kenji Yokota
Journal of General Plant Pathology 2022.03
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
We evaluated disease suppression by surfactin and iturin A against Pseudomonas syringae pv. maculicola MAFF 302783 in Arabidopsis thaliana and its mutants to gain insight into resistance pathways induced. Root treatments revealed that salicylic acid signaling via the isochorismate pathway was the major signaling pathway elicited by both cyclic lipopeptides. Disease suppression was negated after treatment with higher levels of surfactin or iturin A, and this negation of disease suppression was not associated with an antagonistic effect by induction of jasmonate signaling pathway in host plants.
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Comparative study of disease suppression on various host plants by Bacillus cyclic lipopeptides Reviewed
Carla Suzuki Altrão, Takuya Kawashima, Minami Ohbu, Shuhei Matsuura, Misaki Higuchi, Yusuke Yanai, Yuki Hase, Hirosuke Shinohara, Kenji Yokota
Agricultural Sciences 13 2022.01
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
In biological controls using Bacillus spp., cyclic lipopeptides play a role as elicitors to induce disease resistance on various host plants. However, it is still unclear the specificity between cyclic lipopeptides and host plants to induce disease resistance. In this study, we aimed to clarify the specificity to induce disease resistance among cyclic lipopeptides on various host plants. Our data clearly showed both cyclic lipopeptides conferred disease suppression on most of host plants, but at different range of cyclic lipopeptide concen-tration. Our findings contribute to understanding the complex on the specificity of cy-clic lipopeptide derived induced disease resistance.
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Draft Genome Sequence of the Polychlorinated Biphenyl Degrader Comamonas testosteroni Strain YAZ2 Isolated from a Natural Landscape in the Tohoku Region of Japan Reviewed International journal
Tomijiro Hara, Yumiko Takatsuka, Yuh Shiwa, Kenji Yokota
Microbiology Resource Announcements 11 ( 1 ) e00806-21 2022.01
Language：English Publishing type：Research paper (scientific journal)
We report a draft genome sequence of Comamonas testosteroni strain YAZ2, a polychlorinated biphenyl (PCB) degrader that was isolated from a PCB-unpolluted
environment. The assembled genome contains a single 5.4-Mb chromosome and an 87-kb plasmid. The bph gene cluster, which is involved in PCB degradation, was
found on the chromosome. -
Insights into detoxification of tolaasins, the toxins behind mushroom bacterial blotch, by Microbacterium foliorum NBRC 103072T Reviewed International journal
Shun Tomita, Akinobu Kajikawa, Shizunobu Igimi, Hirosuke Shinohara, Kenji Yokota
PhytoFrontiers 2021.03
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
Tolaasins are lipodepsipeptides secreted by Pseudomonas tolaasii, the causal agent of brown blotch disease of mushrooms, and are the toxins that cause the brown spots. We previously reported that Microbacterium foliorum NBRC 103072T is an effective tolaasin-detoxifying bacterium. In this study, we aimed to characterize the tolaasin-detoxification process of M. foliorum NBRC 103072T. The tolaasin-detoxification by M. foliorum NBRC 103072T was carried out by hydrolyzation of tolaasins at two specific sites in the peptide moiety of tolaasins by its cells, and the resulting fragments were released from bacterial cells. The tolaasin-hydrolyzing activity can be extracted by neutral detergent solution from M. foliorum NBRC 103072T cells. Moreover, tolaasin-adsorption to the bacterial cells occurred prior to hydrolyzation of tolaasins, which might contribute to the effective tolaasin-detoxification by M. foliorum NBRC 103072T. It is notable that the tolaasin-degradation process by M. foliorum NBRC 103072T is carried out by hydrolyzation at specific sites in the peptide moiety of lipopeptide by bacterial cells as a novel biological degradation process of cyclic lipopeptides.
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Ligilactobacillus agilis BKN88 possesses thermo-/acid-stable heteropolymeric flagellar filaments Reviewed
Naoto Eguchi, Shunya Suzuki, Kenji Yokota, Shizunobu Igimi, Akinobu Kajikawa
Microbiology 2021.01
Language：English Publishing type：Research paper (scientific journal)
Many flagellated bacteria possess multiple flagellins, but the roles and the compositions of each flagellin are diverse and poorly understood. In Ligilactobacillus agilis BKN88, there are two active flagellin gene paralogues but their function and composition in its flagellar filaments have not been described. The aim of this study is to find the function and composition of the flagellins by employing mutant strains each of which expresses a single flagellin or a modified flagellin. Two single flagellin-expressing strains were both flagellated while the number of flagella per cell in the single flagellin-expressing derivatives was lower than that in the wild type. Nonetheless, these derivative strains were apparently equally motile as the wild type. This indicates that either flagellin is sufficient for cell motility. The immunological activity via Toll-like receptor 5 of the single flagellin-expressing strains or purified single flagellins was readily detectable but mostly variably weaker than that of the wild type. The flagellar filaments of wild type L. agilis BKN88 were more acid-/thermo-stable than those of single flagellin-expressing derivatives. Using a combination of immunoprecipitation and flagellin-specific staining, wild type BKN88 appeared to possess heteropolymeric flagellar filaments consisting of both flagellins and each flagellin appeared to be equally distributed throughout the filaments. The results of this study suggest that the two flagellins together form a more robust filament than either alone and are thus functionally complementary.
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PCR-based screening, isolation, and partial characterization of motile lactobacilli from various animal feces Reviewed
Shunya Suzuki, Koki Fujita, Shintaro Maeno, Yuh Shiwa, Akihito Endo, Kenji Yokota, Shizunobu Igimi, Akinobu Kajikawa
BMC Microbiology 20 2020.06
Language：English Publishing type：Research paper (scientific journal)
Background
Most lactobacilli found in animal intestines are generally non-motile, but there are few exceptions. Our previous work showed that Lactobacillus agilis BKN88, which is a highly motile strain originating from a chicken, takes advantage of motility in gut colonization in murine models, and thus motile lactobacilli likely have unique ecological characteristics conferred by motility. However, the ecology and habitat of gut-derived motile lactobacilli are still rarely understood. In addition, the limited availability of motile Lactobacillus isolates is one of the major obstacles for further studies. To gain insight into the ecology and habitat of the motile lactobacilli, we established a routinely applicable detection method for motile lactobacilli using PCR and subsequent selective isolation in semi-solid MRS medium for the collection of additional motile lactobacilli from animal feces.
Results
We applied the PCR detection using motile lactobacilli-specific primers, based on the motor switch protein gene (fliG) of flagella, to 120 animal feces, followed by selective isolation performed using 45 animal feces. As a result, motile lactobacilli were detected in 44 animal feces. In the selective isolation, 29 isolates of L. agilis and 2 isolates of L. ruminis were obtained from 8 animal species.
Conclusions
These results indicated that motile lactobacilli are distributed in different animal species. Moreover, phylogenetic analysis of the L. agilis isolates suggests co-evolution with the host, and adaptation to a particular environmental niche. -
Adsorption of tolaasins, the toxins behind mushroom bacterial blotch, by Microbacterium spp. is insufficient for its detoxification Reviewed
Shun Tomita, Anna Hirayasu, Akinobu Kajikawa, Shizunobu Igimi, Hirosuke Shinohara, Kenji Yokota
Current Microbiology 2020.01
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
Tolaasins are lipodepsipeptides secreted by Pseudomonas tolaasii, the causal agent of bacterial blotch on several kinds of cultivated mushrooms. Our previous study reported on tolaasin detoxification by Microbacterium sp. K3-5 as a potential biocontrol of the disease. In this study, the tolaasin-detoxifying activities of various type strains of Microbacterium spp. were evaluated through chemical and biological assays. The bacterial cells of all tested strains of Microbacterium spp. showed tolaasin I-elimination from liquid phase. However, the toxin activities of tolaasins were still retained on the tolaasin-treated bacterial cells of all Microbacterium strains except M. foliorum NBRC 103072T. Furthermore, intact tolaasin I was recovered from the tolaasin-treated bacterial cells of all tested strains except M. foliorum NBRC 103072T. Our data reveal that Microbacterium spp. can be characterized as effective tolaasin I-eliminating bacteria through cell adsorption, but that this adsorption alone is insufficient for actual tolaasin detoxification. The biological degradation process must be needed to carry out the detoxification.
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Comparative analysis of immunological properties of S-layer proteins isolated from Lactobacillus strains Reviewed
Shunya Suzuki, Kenji Yokota, Shizunobu Igimi, Akinobu Kajikawa
Microbiology 165 188 - 196 2019.01
Language：English Publishing type：Research paper (scientific journal)
Previous studies have suggested that some Lactobacillus S-layer proteins could modulate immune responses. Primary structures of the S-layer proteins are variable, and their immunological differences are poorly understood. In this study, we evaluated the immunological properties of eight distinct S-layer proteins from different Lactobacillus species. We found that removal of the S-layer proteins from the cell surface reduced the immunological activities of Lactobacillus cells in THP-1 cells. Furthermore, the purified S-layer proteins induced the production of IL-12 p40, although their immunological activities varied between the different S-layer proteins. The production of IL-12 p40 was notably induced by the S-layer protein SLP(aly) from Lactobacillus amylolyticus NRIC 0558T. Multiple sequence alignment revealed that the percent identity of the S-layer proteins of the eight strains vary from 10 to 90 %. In particular, N-terminal regions showed high levels of diversity. To obtain more information about their structure and the immunogenicity, truncated and chimeric S-layer proteins were constructed in recombinant E. coli. Profiling of cytokine production in THP-1 cells by truncated and chimeric S-layer proteins suggested that the intact conformation of the N-terminal region of SLP(aly) contributes to high immunogenicity.
DOI： https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.000766
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Disease suppression by the cyclic lipopeptides iturin A and surfactin from Bacillus spp. against Fusarium wilt of lettuce Reviewed
Shohei Fujita, Kenji Yokota
Journal of General Plant Pathology IF:0.741 85 ( 1 ) 44 - 48 2019.01
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
Iturin A and surfactin are antimicrobial cyclic lipopeptides secreted by antagonistic Bacillus strains, and both elicit defence gene expression in host plants. We previously showed that a soil amendment with either of the purified lipopeptides confers suppression against Fusarium yellows of tatsoi (Brassica rapa) caused by the soil-borne pathogen Fusarium oxysporum and that excess amounts of iturin A or surfactin do not confer suppression. Here, we evaluated the impacts of purified iturin A or surfactin against Fusarium wilt of lettuce (Lactuca sativa). As a soil amendment, iturin A and surfactin each conferred suppression of Fusarium wilt of lettuce on diverse lettuce cultivars similar to the results for tatsoi. However, higher concentrations of iturin A (1.88 mg/l of soil or higher) but not of surfactin (up to 7.5 mg/l of soil) negated the suppression. Growth of Fusarium in liquid cultures was suppressed by iturin A but not surfactin.
DOI： https://link.springer.com/article/10.1007/s10327-018-0816-1
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Effects of agriculture on the water quality of the Cisadane river system in West Java, Indonesia Reviewed International coauthorship
Luqman Arif Lubada, Kenji Yokota, Arief Hartono, Rie Miyaura
Tropical Agriculture and Development 62 ( 2 ) 94 - 103 2018.06
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
This study investigates the impact of agriculture on the water quality of the Cisadane River system in West Java, Indonesia by focusing on one stream flowing from an upland area through an intensive agricultural area before merging with the rest of the river system downstream. In total, 25 water samples were collected from this river system over a straight-line distance of ~70 km and an altitudinal difference of 750 m during the dry season of 2015 and the rainy season of 2016. The samples were analyzed to measure the pH, EC, and concentrations of NO3-N, NH4-N, and PO4-P. The average contamination in the water samples during the dry and rainy seasons was 0.61 and 0.45 mg NO3-N L-1, respectively, 0.56 and 0.28 mg NH4-N L-1, respectively, and 0.64 and 0.55 mg PO4-P L-1, respectively. The results revealed that water was contaminated by inorganic P even in the upper stream. Moreover, the spring water in the agriculture-intensive areas of a rural community, which is believed by the locals to be sufficiently clean for use, was found to more be contaminated by nitrogen than the water in the lower part of the river. As the flow of contaminated water can cause eutrophication in estuaries, it is important to characterize the contamination of water systems to encourage the implementation of sustainable water management strategies.
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Detoxification process of tolaasins, lipodepsipeptides, by Microbacterium sp. K3-5 Reviewed
Shun Tomita, Masayuki Sue, Akinobu Kajikawa, Shizunobu Igimi, Hirosuke Shinohara, Kenji Yokota
Bioscience, Biotechnology, and Biochemistry IF1.295 82 ( 8 ) 1455 - 1458 2018.04
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
Tolaasins are antimicrobial lipodepsipeptides. Here, we report the tolaasins-detoxifying properties of Microbacterium sp. K3-5 (K3-5). The detoxification of tolaasins by K3-5 was performed by hydrolyzation of cyclic structure of tolaasins depending on the tolaasin-K3-5 cell interaction. Our data suggest that the cyclic structure of tolaasins is critical for its interaction to target cells.
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Bacterial flora of fruiting bodies of Shiitake mushroom, isolation of tolaasin-detoxifing bacteria, and tolaasin-detoxification properties by Pseudoxanthomonas spp. Reviewed
Kenji Yokota, Takayuki Nanaumi, Shun Tomita, Ok-Kyung KIim Hiromitsu Negishi, Hirosuke Shinohara
Mushroom Science and Biotechnology 25 ( 4 ) 129 - 133 2018.02
Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)
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Decreasing phosphorous sorption using fishpond sediment and goat manure in acid upland soil Reviewed International coauthorship International journal
Arief Hartono, Syaiful Anwar, Avilia Triani Putri, Kenji Yokota
Journal of ISSAAS (International Society for Southeast Asian Agricultural Sciences) 24 ( 1 ) 118 - 126 2018
Authorship：Last author Language：English Publishing type：Research paper (scientific journal)
Fishpond sediment and fishpond water at Petir village, Darmaga, Bogor, Indonesia have the potential as a soil ameliorant due to the nutrient content needed by crops. This present research sought to evaluate the phosphorus (P) sorption characteristics on acid soil Typic Hapludults Darmaga treated with fishpond sediment, fishpond water, goat manure and their combination, as well as conventional fertilizers. The research was conducted from March to August 2015. The treated soil samples were incubated for 1 week and 2 weeks under room temperature. The experimental design was completely randomized design with three replications. After 1 week or 2 weeks of incubation, soil samples from treatments were subjected to P sorption experiment. The data were simulated by Langmuir and Freundlich equations, wherein data was better simulated by the Freundlich equation. The Freundlich P sorption capacity (KF) value from the combined fishpond sediment and goat manure treatment was the lowest after 1 week and 2 weeks of incubation. This treatment had a significantly higher n value than that of control after 1 week of incubation, however after 2 weeks incubation, the n value was not significantly different from the other treatments. From the KF and n values of Freundlich equation, it was suggested that a combination of fishpond sediment and goat manure was the best treatment needed to decrease P sorption capacity. The decrease of P sorption capacity should decrease the rate of P fertilizer applied by farmers.
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Changes in some soil chemical properties and production of sweet potato, Ipomoea batatas (L.) Lam, treated with fishpond sediment and water in Petir village, Darmaga, Bogor, Indonesia Reviewed International coauthorship
Arief Hartono, Kenji Yokota, Tadashi Baba, Bambang Subroto
Journal of International Society for Southeast Asian Agricultural Sciences 22 ( 2 ) 1 - 9 2016.12
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
Bogor is situated about 70 km south of Jakarta, Indonesia. Bogor is situated upstream of the rivers via Jakarta. The water from Salak mountain is used by farmers not only for agriculture but also for fresh water fishponds. The study sought to clarify the nutrient content of fishpond sediment and fishpond water, evaluate their effects on soil chemical properties and determine the production of sweet potato in Petir village, Darmaga, Bogor in September 2013. Fishpond sediment and fishpond water were analyzed for selected chemical properties. The treatments in the field experiment were without any fertilizer, fishpond sediment, fishpond water, combination of fishpond sediment and fishpond water, and conventional fertilizer, arranged in completely randomized design with three replications. After 2 weeks of incubation and before planting sweet potato, the soil samples of each plot were collected and analyzed. Sweet potato were harvested after four months. The results showed that the fishpond sediment contained high levels of total nitrogen and available phosphorus, and very high organic carbon and basic cations (Ca, Mg, K and Na). The fishpond water contained relatively high total inorganic nitrogen and phosphate. From the field experiment, fishpond sediment and fishpond water improved some soil chemical properties better compared to conventional fertilizer. The combination of fishpond sediment and fishpond water was the best treatment as it resulted in the highest sweet potato yield. The results suggested that a combination of fishpond sediment and fishpond water can be recommended as soil ameliorant or fertilizer for sweet potato production.
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Promiscuous DSF production and responsiveness of the Xylella fastidiosa Rpf system Reviewed
Michael Ionescu, Kenji Yokota, Elena Antonova, Angelica Garcia, Ellen Beaulieu, Anthony T. Iavarone, Steven E. Lindow
mBio IF:6.975 7 ( 4 ) 2016.07
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Cell density-dependent regulation of gene expression in Xylella fastidiosa that is crucial to its switching between plant hosts and insect vectors is dependent on RpfF and its production of 2-enoic acids known as diffusible signal factor (DSF). We show that X. fastidiosa produces a particularly large variety of similar, relatively long-chain-length 2-enoic acids that are active in modulating gene expression. Both X. fastidiosa itself and a Pantoea agglomerans surrogate host harboring X. fastidiosa RpfF (XfRpfF) is capable of producing a variety of both saturated and unsaturated free fatty acids. However, only 2-cis unsaturated acids were found to be biologically active in X. fastidiosa X. fastidiosa produces, and is particularly responsive to, a novel DSF species, 2-cis-hexadecanoic acid that we term XfDSF2. It is also responsive to other, even longer 2-enoic acids to which other taxa such as Xanthomonas campestris are unresponsive. The 2-enoic acids that are produced by X. fastidiosa are strongly affected by the cellular growth environment, with XfDSF2 not detected in culture media in which 2-tetradecenoic acid (XfDSF1) had previously been found. X. fastidiosa is responsive to much lower concentrations of XfDSF2 than XfDSF1. Apparently competitive interactions can occur between various saturated and unsaturated fatty acids that block the function of those agonistic 2-enoic fatty acids. By altering the particular 2-enoic acids produced and the relative balance of free enoic and saturated fatty acids, X. fastidiosa might modulate the extent of DSF-mediated quorum sensing.
Importance: X. fastidiosa, having a complicated lifestyle in which it moves and multiplies within plants but also must be vectored by insects, utilizes DSF-based quorum sensing to partition the expression of traits needed for these two processes within different cells in this population based on local cellular density. The finding that it can produce a variety of DSF species in a strongly environmentally context-dependent manner provides insight into how it coordinates the many genes under the control of DSF signaling to successfully associate with its two hosts. Since the new DSF variant XfDSF2 described here is much more active than the previously recognized DSF species, it should contribute to plant disease control, given that the susceptibility of plants can be greatly reduced by artificially elevating the levels of DSF in plants, creating "pathogen confusion," resulting in lower virulence. -
Impact of antimicrobial lipopeptides from Bacillus sp. in suppression of Fusarium yellows of tatsoi Reviewed
Kenji Yokota, Hiroshige Hayakawa
Microbes and Environments IF:2.231 30 ( 3 ) 281 - 283 2015.09
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Iturin A and surfactin are antimicrobial lipopeptides produced by antagonistic Bacillus spp. We herein demonstrated that both lipopeptides amended the soil-mediated suppression of the soil-borne disease, Fusarium yellows of tatsoi (Brassica rapa var. rosularis). Significant disease suppression was conferred by the amendments of purified iturin A or surfactin to soil. However, an excess amount of iturin A or surfactin to soil resulted in the loss of disease suppression activity.。
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Characterization of possible bacterial biocontrol agents, isolated from various plants in Indonesia, against bacterial wilt and damping-off of tomato Reviewed International coauthorship
Yuliar, Koki Toyota, Kenji Yokota
Soil Microorganisms 69 ( 1 ) 39 - 47 2015.04
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
One hundred bacterial strains isolated from various plants grown organically in Indonesia were assessed for their potential biocontrol ability. Phylogenic analysis based on the 16S rRNA analysis showed that Gram positive and negative bacteria were distributed in the host plants. About 43% of them belonged to Bacillus spp. and the other genera were Achromobacter, Acinetobacter, Agrobacterium, Alcaligenes, Brevibacterium, Enterobacter, Leucobacter, Microbacterium, Paenibacillus, Pseudomonas, Serratia, and Stenotrophomonas. The screening results showed that strains EB13, EB45, and EB53 isolated from Brassica chinensis, Fragaria vesca, and Ipomea aquatica, which were identified as B. amyloliquefaciens, B. cereus, and Alcaligenes sp., increased the survivability of tomato in bacterial wilt (BWT) significantly (P<0.05) by 67%, 83%, and 72%, respectively. Two strains, EB13 and EB45, also increased the survivability of tomato in damping-off significantly (P<0.05) by 45%, while EB53 and EB87 identified as Enterobacter gergoviae showed 23% and 34% disease suppression, respectively, although the differences were not significant. EB13rifkan, EB53rif and EB87rif, spontaneous antibiotics mutants of the parent strains, were confirmed to colonize tomato roots and suppress the population of Rhizoctonia solani in soil and root A seven-day culture broth of strains EB13 and EB87 and its butanol extract showed antibiosis to R. solani and R. solanacearum. HPLC analysis revealed the productions of iturin and surfactin by EB13 and an iturin-like compound by EB87. These results indicate that plant-derived bacteria not only offer potential biocontrol agents for the two tomato diseases but also provide a new source for antibiotics iturin and surfactin.
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The hygroscopic biosurfactant syringafactin produced by Pseudomonas syringae enhances fitness on leaf surfaces during fluctuating humidity Reviewed
Adrien Burch, Viktoria Zeisler, Kenji Yokota, Lukas Schreiber, Steven Lindow
Environmental Microbiology IF:5.756 16 ( 7 ) 2086 - 2098 2014.07
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Biosurfactant production by bacteria on leaf surfaces is poorly documented, and its role in this habitat has not been explored. Therefore, we investigated the production and fitness benefits of syringafactin by Pseudomonas syringae pv. syringae B728a on leaves. Syringafactin largely adsorbed to the waxy leaf cuticle both when topically applied and when produced by cells on plants. Syringafactin increased the rate of diffusion of water across isolated cuticles and attracted water to hydrophobic surfaces exposed to high relative humidity due to its hygroscopic properties. While a wild-type and syringafactin mutant exhibited similar fitness on bean leaves incubated in static conditions, the fitness of the wild-type strain was higher under fluctuating humidity conditions typical of field conditions. When co-inoculated onto either the host plant bean or the non-host plant romaine lettuce, the proportion of viable wild-type cells recovered from plants relative to that of a mutant unable to produce syringafactin increased 10% over 10 days. The number of disease lesions incited by the wild-type strain on bean was also significantly higher than that of the syringafactin mutant. The production of hygroscopic biosurfactants on waxy leaf surfaces apparently benefits bacteria by both attracting moisture and facilitating access to nutrients.
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Agriculture and Water Use in Rural Areas as a Source of Water Pollution in Java -The Case of Petir Village, Bogor Regency, Indonesia- Reviewed
Rie Miyaura, Maki Hayashida, Kenji Yokota
Journal of Agriculture Science, Tokyo University of Agriculture 59 ( 1 ) 52 - 62 2014.06
Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)
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Diffusible Signal Factor (DSF) Synthase RpfF of Xylella fastidiosa Is a Multifunction Protein Also Required for Response to DSF Reviewed
Michael Ionescu, Clelia Baccari, Aline da Silva, Angelica Garcia, Kenji Yokota, Steven Lindow
Journal of Bacteriology IF:3.194 195 ( 23 ) 5273 - 5284 2013.12
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Xylella fastidiosa, like related Xanthomonas species, employs an Rpf cell-cell communication system consisting of a diffusible signal factor (DSF) synthase, RpfF, and a DSF sensor, RpfC, to coordinate expression of virulence genes. While phenotypes of a ΔrpfF strain in Xanthomonas campestris could be complemented by its own DSF, the DSF produced by X. fastidiosa (XfDSF) did not restore expression of the XfDSF-dependent genes hxfA and hxfB to a ΔrpfF strain of X. fastidiosa, suggesting that RpfF is involved in XfDSF sensing or XfDSF-dependent signaling. To test this conjecture, rpfC and rpfF of X. campestris were replaced by those of X. fastidiosa, and the contribution of each gene to the induction of a X. campestris DSF-dependent gene was assessed. As in X. fastidiosa, XfDSF-dependent signaling required both X. fastidiosa proteins RpfF and RpfC. RpfF repressed RpfC signaling activity, which in turn was derepressed by XfDSF. A mutated X. fastidiosa RpfF protein with two substitutions of glutamate to alanine in its active site was incapable of XfDSF production yet enabled a response to XfDSF, indicating that XfDSF production and the response to XfDSF are two separate functions in which RpfF is involved. This mutant was also hypervirulent to grape, demonstrating the antivirulence effects of XfDSF itself in X. fastidiosa. The Rpf system of X. fastidiosa is thus a novel example of a quorum-sensing signal synthase that is also involved in the response to the signal molecule that it synthesizes.
DOI： https://doi.org/10.1128%2FJB.00713-13
Other Link： http://jb.asm.org/content/195/23/5273.abstract
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Selecting a Research Site for Regional Agricultural Development Model -A Case of Promoting Local Products in Rural Areas of Bogor, Indonesia- Reviewed
Rie Miyaura, Hiroki Inaizumi, Akimi Fujimoto, Kenji Yokota, Hironobu Shiwachi, Tadashi Baba
Journal of Agriculture Science, Tokyo University of Agriculture 58 ( 3 ) 170 - 179 2013.12
Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)
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Characterization of a Diffusible Signaling Factor from Xylella fastidiosa Reviewed
Ellen D Beaulieu, Michael Ionescu, Subhadeep Chatterjee, Kenji Yokota, Dirk Trauner, Steven E Lindow
mBio IF:5.311 4 ( 1 ) 2013.01
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Cell-cell signaling in Xylella fastidiosa has been implicated in the coordination of traits enabling colonization in plant hosts as well as insect vectors. This cell density-dependent signaling has been attributed to a diffusible signaling factor (DSF) produced by the DSF synthase RpfF. DSF produced by related bacterial species are unsaturated fatty acids, but that of X. fastidiosa was thought to be different from those of other taxa. We describe here the isolation and characterization of an X. fastidiosa DSF (XfDSF) as 2(Z)-tetradecenoic acid. This compound was isolated both from recombinant Erwinia herbicola expressing X. fastidiosa rpfF and from an X. fastidiosa rpfC deletion mutant that overproduces DSF. Since an rpfF mutant is impaired in biofilm formation and underexpresses the hemagglutinin-like protein-encoding genes hxfA and hxfB, we demonstrate that these traits can be restored by ca. 0.5 µM XfDSF but not by myristic acid, the fully saturated tetradecenoic acid. A phoA-based X. fastidiosa biosensor that assesses DSF-dependent expression of hxfA or hxfB revealed a high level of molecular specificity of DSF signaling.
Importance: X. fastidiosa causes diseases in many important plants, including grape, where it incites Pierce's disease. Virulence of X. fastidiosa for grape is coordinated by cell-cell signaling molecules, designated DSF (Diffusible Signaling Factor). Mutants blocked in DSF production are hypervirulent for grape, suggesting that virulence is suppressed upon DSF accumulation and that disease could be controlled by artificial elevation of the DSF level in plants. In this work, we describe the isolation of the DSF produced by X. fastidiosa and the verification of its biological activity as an antivirulence factor. We also have developed X. fastidiosa DSF biosensors to evaluate the specificity of cell-cell signaling to be investigated.DOI： https://doi.org/10.1128/mBio.00539-12
Other Link： http://mbio.asm.org/content/4/1/e00539-12.full.pdf+html
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Comparative study on sample preparation methods for the HPLC quantification of iturin from culture supernatant of an antagonistic Bacillus strain Reviewed
Kenji Yokota, Maiko Yatsuda, Eitaro Miwa, Kyoko Higuchi
Journal of International Society for Southeast Asian Agricultural Sciences 18 ( 1 ) 70 - 75 2012.06
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Iturin is one of the antimicrobial cyclic lipopeptides produced by antagonistic strains of Bacillus
spp. This study evaluated sample preparation methods for high-performance liquid chromatography
(HPLC) quantification of iturin from culture supernatant of an iturin-producing Bacillus strain. The
acid precipitation and methanol extraction (APME) method showed a lower efficiency than the
butanol extraction and methanol substitution (BEMS) method. Direct application of culture
supernatant to HPLC analysis showed the lowest efficiency. The BEMS method was the most
effective method for quantifying the amount of iturin from culture supernatant based on the percent
recovery and the time required to perform the analysis. -
Effect of inorganic ions on bud cell formation by Fusarium oxysporum in potato dextrose broth Reviewed
Kenji Yokota, Takuma Teraoka, Hirofumi Suzuki, Keiichi Murakami, Eitaro Miwa, Kyoko Higuchi
Journal of General Plant Pathology IF:0.687 76 ( 3 ) 331 - 335 2010.10
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Potato dextrose broth (PDB), a well-known medium for cultivation of fungi, can be made from potato extract and glucose (handmade PDB) or bought as a commercial powder (commercial PDB). Previously, we reported that bud cell formation and fungal biomass of Fusarium oxysporum in handmade PDB are higher than in commercial PDB, and the presence of high molecular weight (>20 MDa) carbohydrates in PDB promoted bud cell formation by most strains of F. oxysporum. In this study, we report the effects of inorganic ions in PDB on bud cell formation and fungal biomass production by F. oxysporum. Concentrations of Mg, K, Fe, PO4 3− and SO4 2− were higher and of Na and Cl− were lower in handmade PDB than in commercial PDB. Adding each inorganic ion alone to commercial PDB showed that Mg is critical for enhancement of bud cell formation by some strains of F. oxysporum. The addition of Mg2+ with raw potato starch to commercial PDB promoted bud cell formation by some, but not all, of the seven F. oxysporum strains tested in this study.
DOI： https://doi.org/10.1007/s10327-010-0256-z
Other Link： http://link.springer.com/article/10.1007%2Fs10327-010-0256-z
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Effect of high molecular weight carbohydrates on bud cells formation by Fusarium oxysporum in potato dextrose broth Reviewed
Kenji Yokota, Takuma Teraoka, Yoshimasa Tsujii, Hirofumi Suzuki, Keiichi Murakami, Eitaro Miwa, Kyoko Higuchi
Journal of General Plant Pathology IF:0.687 76 ( 3 ) 219 - 224 2010.06
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Potato dextrose broth (PDB), one of the most popular culture media for fungi, can be made in the laboratory from potato extract and glucose (handmade PDB) and also bought as powder (commercial PDB). We compared growth of Fusarium oxysporum in handmade and commercial PDBs. For seven strains tested, bud cell formation and fungal biomass were higher in handmade PDB than in commercial PDB. Gel filtration analyses revealed that handmade PDB contained carbohydrates with molecular weights >20 MDa, while most carbohydrates in commercial PDB were <45 kDa. Freshly prepared, raw potato starch had a molecular weight >20 MDa and enhanced bud cell formation by five of seven strains when added to commercial PDB. The addition of glucose to commercial PDB promoted biomass production but not bud cell formation. Furthermore, in a semisynthetic medium containing raw potato starch, bud cell formation was enhanced for all strains tested. These results indicate that the high molecular carbohydrates present in raw potatoes enhanced bud cell formation by Fusarium oxysporum.
DOI： https://doi.org/10.1007/s10327-010-0238-1
Other Link： http://link.springer.com/article/10.1007%2Fs10327-010-0238-1
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Biocontrol of yellow disease of Brassica campestris caused by Fusarium oxysporum with Trichoderma viride under field conditions Reviewed
Ryota Kataoka, Kenji Yokota, Itsuo Goto
Archives of Phytopathology and Plant Protection 43 ( 9 ) 900 - 909 2010.06
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
Trichoderma viride was selected from three species of Trichoderma and was applied to the soil for biocontrol of yellow disease of Brassica campestris caused by Fusarium oxysporum. The population density of F. oxysporum averaged 103 to 104 cfu/g of soil in eight greenhouses. Moreover, the results of application of T. viride showed that the yellow disease of the first, second, and third crops in greenhouse A was 33%, 48%, and 35% in control plot, while it was 1.4%, 11.5%, and 3.0% in T. viride plots, respectively. Also in greenhouse B, the yellow disease of the first crop was inhibited by T. viride compared with control. However, the suppressive effect of T. viride declined on the second crop. Therefore, the third crop was not cultured in greenhouse B. The population density of T. viride in greenhouse A, in which yellow disease was successfully controlled, was higher than that in greenhouse B.
DOI： https://doi.org/10.1080/03235400802075583
Other Link： http://www.tandfonline.com/doi/pdf/10.1080/03235400802075583
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Differentiation of Iturin A Productivity by the Combination of Bacillus subtilis NB22 with organic matter Reviewed
Kenji Yokota, Shizuka Hirai, Nobuhiro Kondo
Journal of International Society for Southeast Asian Agricultural Sciences 13 ( 3 ) 91 - 95 2008.04
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Bacillus subtilis NB22 (NB22) is an Iturin A producing bacteria isolated from compost. Iturin A and its related compounds show antifungal activity for several plant pathogens. In this study, Iturin A productivity was estimated by NB22 on 5 organic matters, soybean cake, soybean curd residue, wheat bran, rapeseed cake, and spent grain and hop. NB22 grew from an initial concentration of 10 sup 7 to approximately 10 sup 10 cfu/g FW in 5 days on 4 kinds of organic matters without spent grain and hop. On the other hand, Iturin A productivity of soybean cake culture was two times higher than the others. The data showed that the selection of organic matter as solid state media for Bacillus spp. was one of the critical points for the productivity of Iturin A.
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Ensuring Sufficient Yeild and High-Palatability Rice Cultivated through the Direct Sowing with Recycled-Paper Mulch in Japan Reviewed
Mayuko Okabe, Tadashi Baba, Masahiro Kamei, Kenji Yokota, Kazuo Suyama
Journal of International Society for Southeast Asian Agricultural Sciences 13 ( 3 ) 62 - 68 2008.04
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Direct sowing with recycled-paper mulch has the constraint of an unstable seedling emergence, but has the possibility of substantial labor saving in organic rice cultivation. Direct sowing with recycled-paper mulch was conducted towards overcoming its defects using cultivar Koshihikari. The percentage of emergence was higher than 70%, and that of established hills was lower than 15% because of bird damage after emergence in 2005. In 2006, an early sowing date was effective for recovering the percentage of established hills up to 76% without the use of many strings as barriers against birds. Yield had a 19% reduction as compared with conventional cultivation in 2006. The rice cultivated using paper mulch had low palatability because the protein content was 1% higher than the commonly cultivated rice in 2005, presumably resulting from the excess absorption of nitrogen supplied from the mulch paper. High palatability rice was obtained through the reduction of nitrogen application as a single basal dressing of organic fertilizer. Since the percentage of established hills highly depends on the conditions of each plot, the evaluation of adaptability for direct sowing was required for each paddy field to ensure sufficient yield.
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Identification of serine138 residue in the 4-residue segment K135K1361137S138 of LukS-I component of Staphylococcus intermedius leukocidin crucial for the LukS-I-specific function of staphylococcal leukocidin Reviewed
Akihito Nishiyama, Marie Antonette Ruth V Guerra, Noriko Sugawara, Kenji Yokota, Jun Kaneko, Yoshiyuki Kamio
Bioscience, Biotechnology, and Biochemistry 66 ( 2 ) 328 - 335 2002.02
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Luk-I produced by Staphylococcus intermedius was found to be a new member of the staphylococcal bi-component pore-forming toxin family, in which staphylococcal leukocidin, Panton-Valentine leukocidin, and gamma-hemolysin are included. Luk-I consists of LukS-I and LukF-I. From the deduced amino acid sequence of LukS-I, a 4-residue sequence, K135K1361137S138, at the root of the stem region was found to be identical with that of the phosphorylated segment of a protein phosphorylated by protein kinase A. A mutant of LukS-I (MLSI-SA), in which the Ser138 residue was replaced by an alanine residue, was created, purified, and assayed for its leukocytolytic and pore-forming activities with LukF-I. Both LukS-I and MLSI-SA formed a ring-shaped complex with LukF-I on rabbit erythrocytes and human polymorphonuclear leukocytes (HPMNLs) membrane. However, MLSI-SA showed no leukocytolytic activity with LukF-I. LukS-I was phosphorylated by protein kinase A in the presence of [gamma-32P] ATP in a cell-free system, but MLSI-SA was not phosphorylated significantly. A potent and selective inhibitor of protein kinase A (N-[2(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89)) showed 50% inhibition of the Luk-I-induced cell lysis at 0.5 nM. Thus, it is concluded that the phosphorylation of the Ser138 residue in the 4-residue segment K135K1361137S138 of LukS-I is important for the leukocytolysis of HPMNLs.
DOI： https://doi.org/10.1271/bbb.66.328
Other Link： https://www.jstage.jst.go.jp/article/bbb/66/2/66_2_328/_pdf
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Tyrosine72 Residue at the Bottom of Rim Domain in LukF Crucial for the Sequential Binding of the Staphylococcal gamma-Hemolysin to Human Erythrocytes Reviewed
Kenji Yokota, Yoshiyuki Kamio
Bioscience, Biotechnology, and Biochemistry 64 ( 12 ) 2744 - 2747 2000.12
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Staphylococcal bi-component cytotoxins, leukocidin (Luk), Panton-Valentine leukocidin (PVL), and γ-hemolysin (Hlg) consist of LukF and LukS, LukF-PV and LukS-PV, and LukF and Hlg2, respectively, and Luk and Hlg share LukF. LukF-PV can not substitute for LukF for Hlg, despite 73% identity in amino acid sequence and close similarity in the 3-dimensional structure between them. Here, we demonstrated that the absence of hemolytic activity of LukF-PV in cooperation with Hlg2 is due to the failure of the binding of LukF-PV to human erythrocytes. We identified Y72 residue at the bottom of rim domain in LukF as the crucial residue for its binding, which is a prerequisite to the subsequent binding of Hlg2 to human erythrocytes. The data obtained showed that a mutant of LukF-PV in which T71 residue was replaced by the corresponding residue of LukF, Y72, endowed LukF-PV with the binding capability to human erythrocytes which was accompanied by its hemolytic activity in the presence of Hlg2.
DOI： https://doi.org/10.1271/bbb.64.2744
Other Link： https://www.jstage.jst.go.jp/article/bbb/64/12/64_12_2744/_pdf
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Crystal Structure of Staphylococcal LukF Delineates Conformational Changes Accompanying Formation of a Transmembrane Channel Reviewed International coauthorship
Rich Olson, Hirofumi Nariya, Kenji Yokota, Yoshiyuki Kamio, Eric Gouaux
Nature Structural Biology IF:13.563 6 ( 2 ) 134 - 140 1999.02
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Staphylococcal LukF, LukS, HgammaII, and alpha-hemolysin are self-assembling, channel-forming proteins related in sequence and function. In the alpha-hemolysin heptamer, the channel-forming beta-strands and the amino latch make long excursions from the protomer core. Here we report the crystal structure of the water soluble form of LukF. In the LukF structure the channel-forming region folds into an amphipathic, three-strand beta-sheet and the amino latch forms a beta-strand extending a central beta-sheet. The LukF structure illustrates how a channel-forming toxin masks protein-protein and protein-membrane interfaces prior to cell binding and assembly, and together with the alpha-hemolysin heptamer structure, they define the end points on the pathway of toxin assembly.
DOI： https://doi.org/10.1038/5821
Other Link： http://www.nature.com/nsmb/journal/v6/n2/full/nsb0299_134.html
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Further Study on the Two Pivotal Parts of Hlg2 for the Full Hemolytic Activity of Staphylococcal gamma-Hemolysin Reviewed
Kenji Yokota, Noriko Sugawara, Hirofumi Nariya, Jun Kaneko, Toshio Tomita, Yoshiyuki Kamio
Bioscience, Biotechnology, and Biochemistry 62 ( 9 ) 1745 - 1750 1998.09
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Staphylococcal gamma-hemolysin consists of LukF of 34 kDa and Hlg2 (or H gamma II) of 32 kDa, which cooperatively lyse human and rabbit erythrocytes. Our previous data showed that the 5-residue segment K23R24L25A26I27 of Hlg2 is pivotal for the hemolytic activity [Nariya, H. and Kamio, Y., Biosci. Biotechnol. Biochem., 59, 1603-1604 (1997)]. Here, we identify an additional amino acid residue in Hlg2 necessary for the full gamma-hemolysin activity by measuring the toxin activity of Hlg2 mutants in the presence of LukF. The data obtained showed that Arg217 of Hlg2 is an additional pivotal amino acid residue besides the KRLAI segment for the full Hlg2-specific function in gamma-hemolysin. We also report evidence that the Hlg2 mutants showing a low or null hemolytic activity in the presence of LukF towards human erythrocytes had low or no binding activity to the cells, resulting in failure of formation of the ring-shaped pore-forming complex on the erythrocytes.
DOI： https://doi.org/10.1271/bbb.62.1745
Other Link： https://www.jstage.jst.go.jp/article/bbb/62/9/62_9_1745/_pdf