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New insights into virulence mechanisms of rice pathogen Acidovorax avenae subsp. avenae strain RS-1 following exposure to ß-lactam antibiotics.

ABSTRACT: Recent research has shown that pathogen virulence can be altered by exposure to antibiotics, even when the growth rate is unaffected. Investigating this phenomenon provides new insights into understanding the virulence mechanisms of bacterial pathogens. This study investigates the phenotypic and transcriptomic responses of the rice pathogenic bacterium Acidovorax avenae subsp. avenae (Aaa) strain RS-1 to ß-lactam antibiotics especially Ampicillin (Amp). Our results indicate that exposure to Amp does not influence bacterial growth and biofilm formation, but alters the virulence, colonization capacity, composition of extracellular polymeric substances and secretion of Type VI secretion system (T6SS) effector Hcp. This attenuation in virulence is linked to unique or differential expression of known virulence-associated genes based on genome-wide transcriptomic analysis. The reliability of expression data generated by RNA-Seq was verified with quantitative real-time PCR of 21 selected T6SS genes, where significant down-regulation in expression of hcp gene, corresponding to the reduction in secretion of Hcp, was observed under exposure to Amp. Hcp is highlighted as a potential target for Amp, with similar changes observed in virulence-associated phenotypes between exposure to Amp and mutation of hcp gene. In addition, Hcp secretion is reduced in knockout mutants of 4 differentially expressed T6SS genes.

SUBMITTER: Li B

PROVIDER: S-EPMC4768089 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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New insights into virulence mechanisms of rice pathogen Acidovorax avenae subsp. avenae strain RS-1 following exposure to ß-lactam antibiotics.

Li Bin B Ge Mengyu M Zhang Yang Y Wang Li L Ibrahim Muhammad M Wang Yanli Y Sun Guochang G Chen Gongyou G

Scientific reports 20160226

Recent research has shown that pathogen virulence can be altered by exposure to antibiotics, even when the growth rate is unaffected. Investigating this phenomenon provides new insights into understanding the virulence mechanisms of bacterial pathogens. This study investigates the phenotypic and transcriptomic responses of the rice pathogenic bacterium Acidovorax avenae subsp. avenae (Aaa) strain RS-1 to ß-lactam antibiotics especially Ampicillin (Amp). Our results indicate that exposure to Amp ...[more]

PMID: 26915352

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Project description:Determining how a bacterial pathogen responds to its host and other bacterial species by altering gene expression is key to understand its pathogenesis and environmental adaption. Here, we used RNA-Seq to comprehensively and quantitatively assess the transcriptional response of the rice bacterial pathogen Acidovorax avenae subsp. avenae strain RS-1 cultivated in vitro, in vivo and in co-culture with rice rhizobacterium Burkholderia seminalis R456. Results revealed a surprisingly large number of regulatory differences between these conditions indicating adaptation of A. avenae subsp. avenae to specific ecological conditions. In particular, a number of potential virulence factors such as type 3 secretion system proteins were specifically expressed under in vivo conditions, whereas genes whose protein products are involved in inter-bacterial interaction such as auxin efflux carrier, small mechanosensitive ion channel protein, and ureidoglycolate hydrolase were among those specifically up-regulated under co-culture conditions. In addition, global genomic analysis of strain RS-1 identified 406 putative non-coding (nc) RNA genes. Interestingly, 8 ncRNA genes that were uniquely expressed under in vivo may be linked to pathogenicity while 4 ncRNA genes that were uniquely expressed under coculture conditions may be involved in adaption to co-cultivation with B. seminalis. Expression data obtained by RNA-Seq were also confirmed for selected genes by quantitative real-time PCR and two-dimensional gel electrophoresis as well as knockout analysis. Aaa strain RS-1 and B. seminalis strain R456 was isolated from diseased rice plants (Li et al., 2011; Xie et al., 2011) and rice rhizosphere (Zhang et al., 2007; Li et al., 2011), respectively, in our previous studies, and were stored in 20-30% sterile glycerol at -80°C. The samples of Aaa strain RS-1 for in vitro and in vivo analysis were prepared as described before (Ibrahim et al., 2012). The co-culture analysis of Aaa strain RS-1 with B. seminalis strain R456 were conducted according to Ruiz et al. (2009) and Di Cagno et al. (2009). Briefly, Aaa strain RS-1 and B. seminalis strain R456 was inoculated and incubated in chambers of a double culture vessel apparatus separated by a 0.4-μm membrane filter (Millipore Isopore™). In order to avoid the possible contamination during in vivo and co-culture operation, all bacterial samples were further confirmed based on the sequence analysis of 16S-rRNA (Li et al., 2011). Then samples were processed for RNA harvesting, mRNA purification and cDNA synthesis.

Dataset Information

New insights into virulence mechanisms of rice pathogen Acidovorax avenae subsp. avenae strain RS-1 following exposure to ß-lactam antibiotics.

Publications

New insights into virulence mechanisms of rice pathogen Acidovorax avenae subsp. avenae strain RS-1 following exposure to ß-lactam antibiotics.

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