Induction of extracytoplasmic function sigma factors in Bacillus subtilis cells with membranes of reduced phosphatidylglycerol content

Abstract

The Bacillus subtilis gene pgsA, which codes for the phosphatidylglycerophosphate synthase that catalyzes the committed step for the synthesis of phosphatidylglycerol (PG), is essential since Pspac-pgsA cells require IPTG for growth. Removal of the inducer caused a dramatic decrease of PG content in the membranes of cells and retarded growth. At 60 min and 120 min after removal, it was reduced to 14.1% and 8.9% of total lipid, respectively, from an initial content of 28.1%. We conjectured that the activity of some extracytoplasmic function (ECF) sigma factors, most of which are caught and regulated directly by cognate transmembrane anti-sigma factors, are affected by altered lipid composition of the membranes. Induction of the activities of ECF sigma factors (σ M and σ V ) was observed after removal of IPTG, though that of σ V was small. But other ECF sigma factors (σ W , σ X , σ Y , σ YlaC and σ Z ) and the general stress sigmas σ B and σ I were not induced. Especially σ M was activated strongly with the reduction of PG content and sustained a high level of activity, in contrast to the transient activation in PG normal cells after exposure to high salinity. This study demonstrates a new relationship between the alterations of lipid composition in the membranes and the activation of ECF sigma factors.

Repeated triggering of sporulation in Bacillus subtilis selects against a protein that affects the timing of cell division

“…yku (encoding a hypothetical thiol:disulfide oxidoreductase) and sigV contain SNPs, therefore it is uncertain how the functions of these proteins are affected. Nevertheless, the sigV mutation is interesting because sigV is expressed upon cell wall stress (Hashimoto et al, 2009;Hashimoto et al, 2013), perhaps induced by malfunctioning TagE. Although it has been suggested that ECF sigma factor s V is functionally redundant because of regulon overlap (Mascher et al, 2007), mutations tuning s V affinity may still be beneficial.…”

“…The remaining mutated genes are bmrU, yhaU and sigV. bmrU is part of an operon-encoding multidrug transporter Bmr and regulator BmrR and is expressed, for example, under glucose starvation (Petersohn et al, 1999;Petersohn et al, 2001), yhaU encodes a K þ /H þ antiporter for K þ efflux (Fujisawa et al, 2007) and sigV encodes one of seven extracytoplasmic function (ECF) sigma factors and is related to cell envelope homeostasis and antibiotic resistance (Mascher et al, 2007;Hashimoto et al, 2009Hashimoto et al, , 2013Matsuoka et al, 2011).…”

Specific roles of phosphatidylglycerols in hosts and microbes

“…The sigma factor can be released from its inhibitor upon receiving a stimulus from the environment, thereby coupling cytoplasmic transcriptional response to extracellular signals. In E coli, acute drop in membrane PG content (by removing a synthetic inducer of a pgsA artificial construct) rapidly induced transcriptional activity of sigma M, which is normally known to mediate responses to high salt exposure (45). This might suggest that detection of changes in membrane PG linked to membrane permeability can be an important component in stress response.…”

Heterologous Expression of theOceanobacillus iheyensisSigW and Its Anti-Protein RsiW inBacillus subtilis

“…31,32) It is suggested that the lipid composition of the membranes is associated with the activity of anti-ECF sigma protein. Judging by the gene annotation of O. iheyensis, its genome lacks pssA and psd (genes for phosphatidylethanolamine synthesis), mprF (a gene for lysylphosphatidylglycerol synthesis), and ugtP (a gene for glycolipids synthesis).…”