AUTHOR=van Beilen Johan , Blohmke Christoph J. , Folkerts Hendrik , de Boer Richard , Zakrzewska Anna , Kulik Wim , Vaz Fred M. , Brul Stanley , Ter Beek Alexander 

TITLE=RodZ and PgsA Play Intertwined Roles in Membrane Homeostasis of Bacillus subtilis and Resistance to Weak Organic Acid Stress

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.01633

DOI=10.3389/fmicb.2016.01633

ISSN=1664-302X

ABSTRACT=<p>Weak organic acids like sorbic and acetic acid are widely used to prevent growth of spoilage organisms such as Bacilli. To identify genes involved in weak acid stress tolerance we screened a transposon mutant library of <italic>Bacillus subtilis</italic> for sorbic acid sensitivity. Mutants of the <italic>rodZ</italic> (<italic>ymfM</italic>) gene were found to be hypersensitive to the lipophilic weak organic acid. RodZ is involved in determining the cell’s rod-shape and believed to interact with the bacterial actin-like MreB cytoskeleton. Since <italic>rodZ</italic> lies upstream in the genome of the essential gene <italic>pgsA</italic> (phosphatidylglycerol phosphate synthase) we hypothesized that expression of the latter might also be affected in <italic>rodZ</italic> mutants and hence contribute to the phenotype observed. We show that both genes are co-transcribed and that both the <italic>rodZ</italic>::mini-Tn<italic>10</italic> mutant and a conditional <italic>pgsA</italic> mutant, under conditions of minimal <italic>pgsA</italic> expression, were sensitive to sorbic and acetic acid. Both strains displayed a severely altered membrane composition. Compared to the wild-type strain, phosphatidylglycerol and cardiolipin levels were lowered and the average acyl chain length was elongated. Induction of <italic>rodZ</italic> expression from a plasmid in our transposon mutant led to no recovery of weak acid susceptibility comparable to wild-type levels. However, <italic>pgsA</italic> overexpression in the same mutant partly restored sorbic acid susceptibility and fully restored acetic acid sensitivity. A construct containing both <italic>rodZ</italic> and <italic>pgsA</italic> as on the genome led to some restored growth as well. We propose that RodZ and PgsA play intertwined roles in membrane homeostasis and tolerance to weak organic acid stress.</p>