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Molecular mechanism of the smart attack of pathogenic bacteria on nematodes.

ABSTRACT: Nematode-bacterial associations are far-reaching subjects in view of their impact on ecosystems, economies, agriculture and human health. There is still no conclusion regarding which pathogenic bacteria sense nematodes. Here, we found that the pathogenic bacterium Bacillus nematocida B16 was sensitive to C. elegans and could launch smart attacks to kill the nematodes. Further analysis revealed that the spores of B. nematocida B16 are essential virulence factors. Once gaseous molecules (morpholine) produced from C. elegans were sensed, the sporulation of B16 was greatly accelerated. Then, B16 showed maximum attraction to C. elegans during the spore-forming process but had no attraction until all the spores were formed. The disruption of either the spore formation gene spo0A or the germination gene gerD impaired colonization and attenuated infection in B16. In contrast, complementation with the intact genes restored most of the above-mentioned deficient phenotypes, which indicated that the spo0A gene was a key factor in the smart attack of B16 on C. elegans. Further, transcriptome, molecular simulations and quantitative PCR analysis showed that morpholine from C. elegans could promote sporulation and initiate infection by increasing the transcription of the spo0A gene by decreasing the transcription of the rapA and spo0E genes. The overexpression of rapA or spo0E decreased the induced sporulation effect, and morpholine directly reduced the level of phosphorylation of purified recombinant RapA and Spo0E compared to that of Spo0A. Collectively, these findings further support a 'Trojan horse-like' infection model. The significance of our paper is that we showed that the soil-dwelling bacterium B. nematocida B16 has the ability to actively detect, attract and attack their host C. elegans. These studies are the first report on the behaviours, signalling molecules and mechanism of the smart attack of B16 on nematodes and also reveal new insights into microbe-host interactions.

SUBMITTER: Zhang L

PROVIDER: S-EPMC7111092 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Molecular mechanism of the smart attack of pathogenic bacteria on nematodes.

Zhang Lin L Wei Yuping Y Tao Ye Y Zhao Suya S Wei Xuyang X Yin Xiaoyan X Liu Suyao S Niu Qiuhong Q

Microbial biotechnology 20191115 3

Nematode-bacterial associations are far-reaching subjects in view of their impact on ecosystems, economies, agriculture and human health. There is still no conclusion regarding which pathogenic bacteria sense nematodes. Here, we found that the pathogenic bacterium Bacillus nematocida B16 was sensitive to C. elegans and could launch smart attacks to kill the nematodes. Further analysis revealed that the spores of B. nematocida B16 are essential virulence factors. Once gaseous molecules (morpholin ...[more]

PMID: 31730281

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Project description:BackgroundThe present study dealt with the screening of soil bacteria with antibacterial activity from different locations in Bangalore, India. Antibiotics play the role of self-defense mechanism for the bacteria and are produced as secondary metabolites to protect themselves from other competitive microorganisms. The need for new antibiotics arose as the pathogenic bacteria acquire resistance to various antibiotics meant for treating human diseases. Given the importance of antibiotics of bacterial origin, standard techniques have been used to isolate and characterize the soil bacteria which showed antibacterial activity.ResultsThe isolated bacteria were tested against human pathogenic bacteria like Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae by primary and secondary screening methods. The isolates PR1, PR2, and PR3 were confirmed to have antibacterial activity against S. aureus, E. coli, P. aeruginosa, and K. pneumoniae by both methods. Studies on the effect of filter sterilization, autoclaving, and proteinase K treatment on culture filtrates showed filter sterilization as the best method. The effect of different carbon and nitrogen sources on the antibacterial activity showed that preference by each isolate differed for carbon and nitrogen requirements. The isolates PR1, PR2, and PR3 were identified as Bacillus aryabhattai strain PR-D07, Arthrobacter humicola strain PR-F07, and Neomicrococcus lactis strain PR-F11 through 16S rRNA sequencing.ConclusionFindings from this research work are encouraging and could proceed further to applied aspects. Only 3 bacterial isolates out of 263 isolates from soil samples displayed antibacterial activity against human pathogens S. aureus, E. coli, P. aeruginosa, and K. pneumoniae. They were identified as B. aryabhattai, A. humicola, and N. lactis by 16S rRNA studies and all of them are Gram-positive. Each isolate preferred different carbon and nitrogen sources for their enhanced antibacterial activity. Efficacy of the culture filtrates of these isolates was tested by filter sterilization, autoclaving, and proteinase K treatment. Filter-sterilized culture filtrates showed higher antibacterial activity than other treatments. A comparison of the antibacterial activity of culture filtrates and antibiotic streptomycin produced an inhibition zone of 18.5 mm and 15.5 mm respectively. This is the first report on the antibacterial activity of all the 3 bacterial strains (B. aryabhattai strain PR-D07, A. humicola strain PR-F07, and N. lactis strain PR-F11), against all the human pathogens, mentioned earlier. It is also found that the antibiotic factor is proteinaceous as proteinase K considerably reduced the antibacterial activity of the culture filtrates. With the above significant results, these 3 bacteria are considered to be promising candidates for the isolation of new antibacterial agents.

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Molecular mechanism of the smart attack of pathogenic bacteria on nematodes.

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Molecular mechanism of the smart attack of pathogenic bacteria on nematodes.

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