title: Whole-genome expression profiling of Bradyrhizobium japonicum in response to hydrogen peroxide.
abstract: Bradyrhizobium japonicum, a nitrogen-fixing bacterium in soil, establishes a symbiotic relationship with the leguminous soybean plant. Despite a mutualistic association between the two partners, the host plant produces an oxidative burst to protect itself from the invasion of rhizobial cells. We investigated the effects of H(2)O(2)-mediated oxidative stress on B. japonicum gene expression in both prolonged exposure (PE) and fulminant shock (FS) conditions. In total, 439 and 650 genes were differentially expressed for the PE and FS conditions, respectively, at a twofold cut-off with q < 0.05. A number of genes within the transport and binding proteins category were upregulated during PE and a majority of those genes are involved in ABC transporter systems. Many genes encoding ? factors, global stress response proteins, the FixK(2) transcription factor, and its regulatory targets were found to be upregulated in the FS condition. Surprisingly, catalase and peroxidase genes which are typically expressed in other bacteria under oxidative stress were not differentially expressed in either condition. The isocitrate lyase gene (aceA) was induced by fulminant H(2)O(2) shock, as was evident at both the transcriptional and translational levels. Interestingly, there was no significant effect of H(2)O(2) on exopolysaccharide production at the given experimental conditions.
authors.affiliation: Department of Biology, University of Texas, Arlington, TX, USA.
authors.forename: Jeong-Min
authors.initials: JM
authors.lastname: Jeon
authors.forename: Hae-In
authors.initials: HI
authors.lastname: Lee
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Donati
authors.forename: Jae-Seong
authors.initials: JS
authors.lastname: So
authors.forename: David W
authors.initials: DW
authors.lastname: Emerich
authors.forename: Woo-Suk
authors.initials: WS
authors.lastname: Chang
mesh_terms: D020369:Bradyrhizobium / Q000187:drug effects* / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D004790:Enzyme Induction; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects* / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D005816:Genetic Complementation Test; D016680:Genome, Bacterial / Q000235:genetics; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007522:Isocitrate Lyase / Q000096:biosynthesis / Q000187:drug effects; D050296:Microbial Viability; D009586:Nitrogen Fixation; D020411:Oligonucleotide Array Sequence Analysis; D016877:Oxidants / Q000494:pharmacology*; D018384:Oxidative Stress; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D013559:Symbiosis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D059467:Transcriptome
chemical_list: D016877:Oxidants; D011135:Polysaccharides, Bacterial; D014157:Transcription Factors; D006861:Hydrogen Peroxide; D007522:Isocitrate Lyase