Transcriptional responses during outgrowth of Bacillus subtilis endospores.

The Bacillus subtilis 168 genome contains an array of alternative sigma factors, many of which play important roles in reprogramming expression during stress and sporulation. The role of the different sigma factors during outgrowth, when the germinated endospore is converted back to a vegetative cell, is less well characterized. The activity of the alternative sigma factors sigmaB, sigmaD and sigmaH during endospore outgrowth was analysed by Northern blotting and lacZ reporter assays. While sigmaD and sigmaH were transcriptionally active during outgrowth, sigmaB-dependent transcription was not observed until after the first cell division, when growth slowed. Using an IPTG-controllable copy of sigA, an optimal level of expression was required to maintain growth rate at the end of outgrowth. The genes encoding the putative extracytoplasmic function (ECF) sigma factors sigmaI, sigmaV, sigmaW, sigmaZ and YlaC were insertionally inactivated using pMUTIN4. These strains, together with sigM and sigX mutants, were tested to determine their role and measure their expression during endospore outgrowth. Transcripts or beta-galactosidase activity were observed for each of the ECF sigma factors early after germination. With the exception of MJH003 (sigM), which showed an exacerbated salt stress defect, inactivation of the ECF sigma factor genes did not affect outgrowth in the conditions tested.

GerN, an antiporter homologue important in germination of Bacillus cereus endospores.

A homologue of the grmA spore germination gene of Bacillus megaterium and of a NaH-antiporter gene (napA) of Enterococcus hirae has been identified in Bacillus cereus 569 (ATCC 10876). The putative protein product has 58 and 43% amino acid identity with GrmA and NapA, respectively. Insertional inactivation of this B. cereus gene, named gerN, did not affect vegetative growth or sporulation. The null mutant spores were 30-fold slower to germinate in inosine (5 mM) but germinated almost normally in response to L-alanine (10 mM). The null mutant spores germinated after several hours with inosine as the sole germinant, but germination was asynchronous and the normal order of germination events was perturbed. At a suboptimal germinant concentration (50 microM), inosine germination was completely blocked in the mutant, while the rate of germination in 50 microM L-alanine was reduced to one-third of that of the wild type. The requirement for GerN function in the response to a particular germinant suggests that a germination receptor may have a specifically associated antiporter, which is required at the initiation of germination and which, in the case of the inosine receptor, is GerN. Since germination in suboptimal concentrations of L-alanine shows a delay, additional germination transporters may be required for optimal response at low germinant concentrations.

Pilo-sebaceous duct physiology. III. Observations on the number and size of pilo-sebaceous ducts in acne vulgaris.

We have used surface microscopy to measure the pil-sebaceous duct orifices at different sites in 150 subjects. Our data have shown that there are more pilo-sebaceous units on the face compared to the back and that these exists are smaller on the face. Despite the small exit the sebum excretion rate per gland on the forehead was not significantly different from that on the back. Thus the number of pilo-sebaceous duct units and the pilo-sebaceous canal exit size are possible factors in the localization of acne.