Microarray analysis of RpoS-mediated gene expression in Escherichia coli K-12.

Area of Science:

• Microbiology
• Bacterial Genetics
• Gene Regulation

Background:

• The alternative sigma factor RpoS (RNA polymerase sigma 70 factor S) is crucial for bacterial adaptation to stress and nutrient deprivation.
• The RpoS regulon in Escherichia coli is extensive but incompletely characterized, particularly regarding its role during stationary phase entry.

Purpose of the Study:

• To comprehensively delineate the RpoS-controlled transcriptome during the entry into stationary phase in E. coli.
• To identify novel RpoS-regulated genes and characterize the extent of both positive and negative regulation.

Main Methods:

• Utilized oligonucleotide microarrays for high-throughput transcriptome analysis.
• Grew E. coli cultures in rich medium to observe gene expression changes during stationary phase entry.
• Validated RpoS control over known and novel genes through expression profiling.

Main Results:

• Confirmed RpoS regulation of known stationary-phase genes, validating the microarray approach.
• Identified over 100 positively regulated genes, with more than 45 newly discovered targets of RpoS.
• Discovered extensive negative regulation by RpoS affecting flagellum biosynthesis, TCA cycle enzymes, and Rac prophage genes.

Conclusions:

• RpoS controls a larger set of genes than previously understood, encompassing both positive and negative regulatory roles.
• Negative regulation by RpoS is a significant factor in bacterial physiology, potentially explaining the growth advantage of rpoS mutants.
• This study provides a more complete picture of the RpoS regulon's contribution to bacterial adaptation and survival.