Each month, a manuscript published in our flagship journal Microbiology is chosen by a member of the Editorial Board. This month, the paper is New envelope stress factors involved in σE activation and conditional lethality of rpoE mutations in Salmonella enterica and was chosen by Dr David Grainger.
Ultra violet radiation has long been known to damage diverse cell types, primarily by inducing the formation of lesions, such as pyrimidine dimers, in DNA. In this work Amar and colleagues report the surprising observation that UV light triggers expression of the σE regulon in Salmonella. Usually activated in response to cell envelope stress, the σE mediated response to UV light appears important for cell survival. This work suggests that the UV damage in bacteria extends beyond mutation of the chromosome.
New envelope stress factors involved in σE activation and conditional lethality of rpoE mutations in Salmonella enterica
Salmonella enterica serovar Typhimurium (S. typhimurium) can cause food- and water-borne illness. A key factor the ability of S. typhimurium to cause disease is a protein called σE. σE is coded for by the gene rpoE
This study reports new stress factors that are able to activate σE expression. We demonstrate that UVA radiation induces σE activity in a pathway that is dependent on the stringent response regulator ppGpp.
σE activity is also induced by hypo-osmotic shock in the absence of osmoregulated periplasmic glucans (OPGs). It is known that the rpoE gene is not essential in S. typhimurium. However, we report here two cases of the conditional lethality of rpoE mutations in this micro-organism.
We demonstrate that rpoE mutations are not tolerated in the absence of OPGs or LPS O-antigen. The latter case resembles that of the prototypic Escherichia coli strain K12, which neither synthesizes a complete LPS nor tolerates null rpoE mutations.
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