Unmasking Novel Sporulation Genes in Bacillus subtilis

Abstract

The Bacillus subtilis transcription factor E directs the expression of a regulon of 262 genes, but null mutations in only a small fraction of these genes severely impair sporulation. We have previously reported that mutations in seven E -controlled genes cause a mild (2-to 10-fold) defect in sporulation. In this study, we found that pairwise combinations of some of these seven mutations led to strong synthetic sporulation phenotypes, especially those involving the ytrHI operon and ybaN. Double mutants of ybaN and ytrH and of ybaN and ytrI had >10,000-fold lower sporulation efficiencies than the wild type. Thin-section electron microscopy revealed a block in cortex formation for the ybaN ytrH double mutant and coat defects for the ybaN single and ybaN ytrI double mutants. Sporulating cells of a ybaN ytrI double mutant and of a ybaN ytrHI triple mutant exhibited a pronounced loss of dipicolinic acid (DPA) between hours 8 and 24 of sporulation, in contrast to the constant levels seen for the wild type. An analysis of the spore cortex peptidoglycans of the ybaN ytrI and ybaN ytrHI mutants showed striking decreases in the levels of total muramic acid by hour 24 of sporulation. These data, along with the loss of DPA in the mutants, suggest that the developing spores were unstable and that the cortex underwent degradation late in sporulation. The existence of otherwise hidden sporulation pathways indicates that functional redundancy may mask the role of hitherto unrecognized sporulation genes.

Physical basis for the adaptive flexibility of Bacillus spore coats

“…We restricted our model to two dimensions, both because the wrinkle morphology is that of long ridges along the spore, and in order to focus on a minimal model. Typical parameter values in our model are as follows: spore radius R coat , and thickness, h, of the coat to be approximately 300 and 40 nm, respectively [2,21,22] (see the electronic supplementary material, table S1), the measured elastic modulus of the B. subtilis coat E approximately 13.6 GPa using an atomic force microscope [23] (AFM), and the energy of adhesion between the coat and the cortex, J, approximately 10 J m…”

Identification and Characterization of a Novel Polysaccharide Deacetylase C (PdaC) from Bacillus subtilis

“…1 shows identified or predicted polysaccharide deacetylases in B. subtilis and some other Gram-positive bacteria. It is known that PdaA and PdaB play roles in sporulation (10,28,29) but the other gene products, YjeA (renamed PdaC), YlxY, YxkH, and YheN, are not associated with sporulation and germination (28). Thus, these disruptants were created, and the sensitivity of these strains toward lysozyme (muramidase that digests a linkage of MurNAc-GlcNAc in peptidoglycan) was determined.…”

Gene Conservation among Endospore-Forming Bacteria Reveals Additional Sporulation Genes in Bacillus subtilis

“…ylxY encodes a probable polysaccharide deacetylase (Table 3) and exhibits some similarity to two B. subtilis genes under sporulation control, namely, pdaA and pdaB, mutants of which display defects in spore cortex maturation (41)(42)(43). The nature of the competition deficit of the ylxY mutant is currently unknown.…”