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The LysR-Type Transcriptional Regulator LeuO Controls Expression of Several Genes in Salmonella enterica Serovar Typhi

2007; American Society for Microbiology; Volume: 190; Issue: 5 Linguagem: Inglês

10.1128/jb.01649-07

1098-5530

Ismael Hernández-Lucas, Ana L. Gallego-Hernández, Sergio Encarnación, Marcos Fernández‐Mora, Ángel G. Martínez-Batallar, Heladia Salgado, Ricardo Oropeza, Edmundo Calva,

Bacterial Genetics and Biotechnology

ABSTRACT LeuO is a LysR-type transcriptional regulator that has been implicated in the bacterial stringent response and in the virulence of Salmonella . A genomic analysis with Salmonella enterica serovar Typhi revealed that LeuO is a positive regulator of OmpS1, OmpS2, AssT, and STY3070. In contrast, LeuO down-regulated the expression of OmpX, Tpx, and STY1978. Transcriptional fusions supported the positive and negative LeuO regulation. Expression of ompS1 , assT , and STY3070 was induced in an hns mutant, consistent with the notion that H-NS represses these genes; transcriptional activity was lower for tpx and STY1978 in an hns background, suggesting that this global regulatory protein has a positive effect. In contrast, ompS2 and ompX expression appeared to be H-NS independent. LeuO specifically bound to the 5′ intergenic regions of ompS2 , assT , STY3070, ompX , and tpx , while it was not observed to bind to the promoter region of STY1978, suggesting that LeuO regulates in direct and indirect ways. In this work, a novel set of genes belonging to the LeuO regulon are described; interestingly, these genes are involved in a variety of biological processes, suggesting that LeuO is a global regulator in Salmonella .