Journal of Microbiology

Research Support, Non-U.S. Gov'ts

NOTE] Identification of Genes That Are Dispensable for Animal Infection by Salmonella typhimurium: Hyun-Ju Kim , Hyon E. Choy; J. Microbiol. 2010;48(3):399-403. Published online June 23, 2010; DOI: https://doi.org/10.1007/s12275-010-9332-5

Abstract: In the current study, we generated a pool of Salmonella typhimurium mutants using the Tn10d-cam minitransposon. This pool of mutants was administered to BALB/c mice through the oral route, and bacteria were recovered from the spleen 3 days post-infection. After three rounds of serial passage, we observed enrichment of two insertion mutants, a yddG insertion and an amyA insertion. These two genes have been implicated in growth on plant products (amyA) and survival in the presence of paraquat (yddG), both of which are natural environments for Salmonella. Thus, while in vivo expression technology has identified S. typhimurium genes that are absolutely necessary for animal infection, other genes involved in vegetative growth also appear to play role in the establishment of pathogenesis.

ppGpp-Mediated Stationary Phase Induction of the Genes Encoded by Horizontally Acquired Pathogenicity Islands and cob/pdu Locus in Salmonella enterica serovar Typhimurium: Miryoung Song , Hyun-Ju Kim , Sangryeol Ryu , Hyunjin Yoon , Jiae Yun , Hyon E. Choy; J. Microbiol. 2010;48(1):89-95. Published online March 11, 2010; DOI: https://doi.org/10.1007/s12275-009-0179-6

Abstract: Salmonella enterica is highly diverse in terms of genome structure, which is at least partly due to the horizontal transfer of genetic elements from various sources. In this study, we examined the expression profiles of such genes in Salmonella Pathogenicity Islands (SPIs) and the cob/pdu locus, horizontally acquired large DNA segments, during growth under standard growth conditions. Transcripts from exponentially growing and early stationary phase Salmonellae were compared using various methods including cDNA microarray analysis. Nearly all genes encoded by SPIs and the cob/pdu locus were induced at the onset of the stationary phase in a stringent molecule ppGpp-dependent but stationary phase σ, σ38-independent manner. Although, it has been suggested that ppGpp acts in concert with DksA, we found the stationary phase induction of those SPI genes was not DksA dependent. It is suggested that ppGpp stimulates the expression of these stress-inducible genes encoded by horizontally acquired DNA, by itself or in concert with DksA.

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