Suppression of Engulfment Defects inBacillus subtilisby Elevated Expression of the Motility Regulon

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Abstract
During Bacillus subtilis sporulation, the transient engulfment defect of spoIIB strains is enhanced by spoVG null mutations and suppressed by spoVS null mutations. These mutations have opposite effects on expression of the motility regulon, as the spoVG mutation reduces and the spoVS mutation increases σD-directed gene expression, cell separation, and autolysis. Elevating σD activity by eliminating the anti-σ factor FlgM also suppresses spoIIB spoVG, and both flgM and spoVS mutations cause continued expression of the σD regulon during sporulation. We propose that peptidoglycan hydrolases induced during motility can substitute for sporulation-specific hydrolases during engulfment. We find that sporulating cells are heterogeneous in their expression of the motility regulon, which could result in phenotypic variation between individual sporulating cells.