Modulating the bacterial surface with small RNAs: a new twist on PhoP/Q-mediated lipopolysaccharide modification

P>In recent years, small non-coding RNAs have emerged as important regulatory components in bacterial stress responses and in bacterial virulence. Many of these are conserved in related species and act on target mRNAs by sequence complementarity. They are tightly controlled at the transcription level, and are frequently elements of global regulatory systems. In Escherichia coli and Salmonella, almost one-third of the functional characterized small RNAs participate in control of outer membrane protein production. A subset of these genes is under the control of the sigma E-signalling system that monitors the folding status of the envelope and interacts with other regulatory systems to integrate multiple signals into a co-ordinated cellular response. In this issue of Molecular Microbiology, Moon and Gottesman describe a novel baseparing small RNA that participates in modulation of bacterial surface properties by regulating lipopolysaccharide modification. The small RNA is expressed as part of the PhoP/PhoQ two-component system that plays a major role in virulence of pathogenic species. This work expands the list of global regulators known to control small RNA expression in enterobacteria and reinforces the idea that one central role of bacterial small regulatory RNAs is to modulate and fine-tune cell surface composition and structure.