TY - JOUR
T1 - Appropriate regulation of the σEd-ependent envelope stress response is necessary to maintain cell envelope integrity and stationary-phase survival in Escherichia coli
AU - Nicoloff, Hervé
AU - Gopalkrishnan, Saumya
AU - Ades, Sarah E.
N1 - Publisher Copyright:
© 2017 American Society for Microbiology. All Rights Reserved.
PY - 2017/6/1
Y1 - 2017/6/1
N2 - The alternative sigma factor σE is a key component of the Escherichia coli response to cell envelope stress and is required for viability even in the absence of stress. The activity of σE increases during entry into stationary phase, suggesting an important role for σE when nutrients are limiting. Elevated σE activity has been proposed to activate a pathway leading to the lysis of nonculturable cells that accumulate during early stationary phase. To better understand σE-directed cell lysis and the role of σE in stationary phase, we investigated the effects of elevated σE activity in cultures grown for 10 days. We demonstrate that high σE activity is lethal for all cells in stationary phase, not only those that are nonculturable. Spontaneous mutants with reduced σE activity, due primarily to point mutations in the region of σE that binds the -35 promoter motif, arise and take over cultures within 5 to 6 days after entry into stationary phase. High σE activity leads to large reductions in the levels of outer membrane porins and increased membrane permeability, indicating membrane defects. These defects can be counteracted and stationary-phase lethality delayed significantly by stabilizing membranes with Mg2+ and buffering the growth medium or by deleting the σE-dependent small RNAs (sRNAs) MicA, RybB, and MicL, which inhibit the expression of porins and Lpp. Expression of these sRNAs also reverses the loss of viability following depletion of σE activity. Our results demonstrate that appropriate regulation of σE activity, ensuring that it is neither too high nor too low, is critical for envelope integrity and cell viability.
AB - The alternative sigma factor σE is a key component of the Escherichia coli response to cell envelope stress and is required for viability even in the absence of stress. The activity of σE increases during entry into stationary phase, suggesting an important role for σE when nutrients are limiting. Elevated σE activity has been proposed to activate a pathway leading to the lysis of nonculturable cells that accumulate during early stationary phase. To better understand σE-directed cell lysis and the role of σE in stationary phase, we investigated the effects of elevated σE activity in cultures grown for 10 days. We demonstrate that high σE activity is lethal for all cells in stationary phase, not only those that are nonculturable. Spontaneous mutants with reduced σE activity, due primarily to point mutations in the region of σE that binds the -35 promoter motif, arise and take over cultures within 5 to 6 days after entry into stationary phase. High σE activity leads to large reductions in the levels of outer membrane porins and increased membrane permeability, indicating membrane defects. These defects can be counteracted and stationary-phase lethality delayed significantly by stabilizing membranes with Mg2+ and buffering the growth medium or by deleting the σE-dependent small RNAs (sRNAs) MicA, RybB, and MicL, which inhibit the expression of porins and Lpp. Expression of these sRNAs also reverses the loss of viability following depletion of σE activity. Our results demonstrate that appropriate regulation of σE activity, ensuring that it is neither too high nor too low, is critical for envelope integrity and cell viability.
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U2 - 10.1128/JB.00089-17
DO - 10.1128/JB.00089-17
M3 - Article
C2 - 28373273
AN - SCOPUS:85019661178
SN - 0021-9193
VL - 199
JO - Journal of bacteriology
JF - Journal of bacteriology
IS - 12
M1 - e00089-17
ER -