Global Analysis of Extracytoplasmic Stress Signaling in Escherichia coli

The Bae, Cpx, Psp, Rcs, and σE pathways constitute the Escherichia coli signaling systems that detect and respond to alterations of the bacterial envelope. Contributions of these systems to stress response have previously been examined individually; however, the possible interconnections between these pathways are unknown. Here we investigate the dynamics between the five stress response pathways by determining the specificities of each system with respect to signal-inducing conditions, and monitoring global transcriptional changes in response to transient overexpression of each of the effectors. Our studies show that different extracytoplasmic stress conditions elicit a combined response of these pathways. Involvement of the five pathways in the various tested stress conditions is explained by our unexpected finding that transcriptional responses induced by the individual systems show little overlap. The extracytoplasmic stress signaling pathways in E. coli thus regulate mainly complementary functions whose discrete contributions are integrated to mount the full adaptive response

Dynamics of the compartmentalized Streptomyces chromosome during metabolic differentiation

Publisher: Cold Spring Harbor Laboratory Section: New ResultsInternational audienceStreptomyces are among the most prolific bacterial producers of specialized metabolites, including antibiotics. The linear genome is partitioned into a central region harboring core genes and two extremities enriched in specialized metabolite biosynthetic gene clusters (SMBGCs). The molecular mechanisms governing structure and function of these compartmentalized genomes remain mostly unknown. Here we show that in exponential phase, chromosome structure correlates with genetic compartmentalization: conserved, large and highly transcribed genes form boundaries that segment the central part of the genome into domains, whereas the terminal ends are transcriptionally, largely quiescent compartments with different structural features. Onset of metabolic differentiation is accompanied by remodeling of chromosome architecture from an open to a rather closed conformation, in which the SMBGCs are expressed forming new boundaries. Altogether, our results reveal that S. ambofaciens linear chromosome is partitioned into structurally distinct entities, indicating a link between chromosome folding, gene expression and genome evolution