New Resources for Genome-Scale Genetic Analysis of Acinetobacter baumannii
Acinetobacter baumannii is a relatively uncharacterized pathogen frequently responsible for antibiotic-resistant infections in health care settings. Gallagher et al. (p. 2027–2035) present a suite of resources for dissecting the genetic basis of clinically relevant traits of reference strain AB5075. The resources include an ordered library of transposon mutants with insertions corresponding to virtually all nonessential genes, an adaptation of transposon mutant pool sequencing (Tn-seq) technology for profiling changes in the makeup of large pools of mutants subjected to growth under selection, and the completion and annotation of the strain's genome sequence.
An Alternative Form of Regulation for an Alternative Respiratory System
Escherichia coli, like many other bacteria, can utilize several compounds as alternative electron acceptors when oxygen is scarce. Most of these anaerobic respiratory pathways are repressed by oxygen. However, the Tor system, which confers the ability to respire trimethylamine oxide (TMAO), is active even when oxygen is present. Roggiani and Goulian (p. 1976–1987) report a peculiar form of oxygen dependence in which aerobic growth leads to high cell-to-cell variability of Tor system expression, without affecting the mean expression level. This oxygen-dependent variability, which originates from the TMAO-sensing phosphorelay, is an unexpected and previously unrecognized form of regulation.
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