The
dgkB gene is essential for the growth of
Bacillus subtilis. It encodes a diacylglycerol (DG) kinase that converts DG to phosphatidic acid to reintroduce it into the phospholipid synthesis pathway. Repression of the
dgkB gene placed under a regulatable promoter causes accumulation of DG and leads to lethality. DG is formed as a byproduct of the synthesis of lipoteichoic acid (LTA), a polyanionic component of the cell envelope.
B. subtilis synthesizes LTA by polymerizing the glycerophosphate moiety of phosphatidylglycerol (PG) onto a glucolipid membrane anchor, and releasing the DG moiety of PG.
B. subtilis has four genes homologous to
Staphylococcus aureus ltaS, which encodes LTA synthase. Disruption of either or both of two genes,
yflE and
yfnI, whose products show higher homology with
S. aureus LtaS among the four homologues, suppressed the lethality caused by
dgkB repression. In cells with
dgkB repression, DG was accumulated to 43 ± 3% of total lipids, about three times the content of wild type cells (13 ± 1%). Disruption of
yfnI in the
dgkB-repressed cells reduced the DG content to 15 ± 2%, but
yflE-disruption did not (42 ± 1%); this was probably due to efficient LTA synthesis by YfnI in the
yflE-disrupted cells. Further introduction of a disrupted allele of
ugtP, encoding glucolipid synthase that consumes DG as a substrate, partially lowered the colony forming capacity in strains with
yflE-disruption. A disrupted
dgkB allele was successfully introduced into strains disrupted for either or both of
yflE and
yfnI, indicating that the essential gene
dgkB is dispensable in mutants defective in LTA synthesis.
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