Protein synthesis in the isolated forespores from sporulating cells of Bacillus subtilis

Prevalence and duration of asymptomatic Clostridium difficile carriage among healthy subjects in Pittsburgh, Pennsylvania

Previous studies suggested that 7 to 15% of healthy adults are colonized with toxigenic Clostridium difficile. To investigate the epidemiology, genetic diversity, and duration of C. difficile colonization in asymptomatic persons, we recruited healthy adults from the general population in Allegheny County, Pennsylvania. Participants provided epidemiological and dietary intake data and submitted stool specimens. The presence of C. difficile in stool specimens was determined by anaerobic culture. Stool specimens yielding C. difficile underwent nucleic acid testing of the tcdA gene segment with a commercial assay; tcdC genotyping was performed on C. difficile isolates. Subjects positive for C. difficile by toxigenic anaerobic culture were asked to submit additional specimens. One hundred six (81%) of 130 subjects submitted specimens, and 7 (6.6%) of those subjects were colonized with C. difficile. Seven distinct tcdC genotypes were observed among the 7 C. difficile-colonized individuals, including tcdC genotype 20, which has been found in uncooked ground pork in this region. Two (33%) out of 6 C. difficile-colonized subjects who submitted additional specimens tested positive for identical C. difficile strains on successive occasions, 1 month apart. The prevalence of C. difficile carriage in this healthy cohort is concordant with prior estimates. C. difficile-colonized individuals may be important reservoirs for C. difficile and may falsely test positive for infections due to C. difficile when evaluated for community-acquired diarrhea caused by other enteric pathogens.

Cloning of a novel gene yrbB, encoding a protein located in the spore integument of Bacillus subtilis

A DNA fragment (2.7 kbp) containing three deduced open reading frames, orf1, orf2 and orf3 (partial sequence), was isolated from the genomic library of Bacillus subtilis using an antiserum raised against spore integument, and was sequenced. orf2 was 519 nucleotides long and encoded a protein of 172 amino acids with a predicted molecular size of 19,552, corresponding to the protein which reacted with the antiserum. Immunoelectron microscopic observation indicated that YrbB, the product of orf2, was located within the spore integument, mainly in the cortex layer with a part in the inner region of the coat layer.

A Bacillus subtilis spore coat polypeptide gene, cotS

A gene, cotS, encoding a spore coat polypeptide of Bacillus subtilis, was isolated from an EcoRI fragment (5.4 kb) of the chromosome by using synthetic oligonucleotide probes corresponding to the NH2-terminal amino acid sequence of Cot40-2 previously purified from the spore coat of B. subtilis. The nucleotide sequence (2603 bp) was determined and sequence analysis suggested the presence of two contiguous ORFs, ORF X and cotS, followed by the 5'-region of an additional ORF, ORF Y, downstream of cotS. The cotS gene is 1053 nucleotides long and encodes a polypeptide of 351 amino acids with a predicted molecular mass of 41083 Da. The predicted amino acid sequence was in complete agreement with the NH2-terminal amino acid sequence of Cot40-2. The orfX gene is 1131 nucleotides long and encodes a polypeptide of 377 amino acids with a predicted molecular mass of 42911 Da. The gene product of cotS was confirmed to be identical to Cot40-2 by SDS-PAGE and immunoblotting from Escherichia coli transformed with a plasmid containing the cotS region. Northern hybridization analysis indicated that a transcript of cotS and orfX appeared at about 5 h after the onset of sporulation. The transcriptional start point determined by primer extension analysis suggested that -10 and -35 regions are present upstream of orfX and are very similar to the consensus sequence for the sigma k-dependent promoter. Terminator-like sequences were not found in the DNA fragment (2603 bp) sequenced in this paper, which suggested that the cotS locus may be part of a multicistronic operon. The cotS gene is located between dnaB and degQ at about 270-275 degrees on the genetic map. Insertional mutagenesis of the cotS gene by introducing an integrative plasmid resulted in no alteration of growth or sporulation, and had no effect on germination or resistance to chloroform.

Purification of Bacillus subtilis spore coat protein by electrophoretic elution procedure and determination of NH2-terminal amino acid sequences

Spore coat protein of Bacillus subtilis was purified by electrophoretic elution procedure. Solubilized coat protein components were separated on SDS-PAGE and the desired protein was recovered from the gel pieces under the optimal condition examined. Two purified polypeptides with molecular weights of about 40 kDa were obtained; each of them was in very closed size on SDS-PAGE, both retaining antigenic activity against anti-spore coat protein serum on immunoblot analysis. The N-terminal 23 and 30 amino acid sequences of them were determined, and they were not identical to each other and also not homologous in the sequences of coat proteins previously reported.

Purification and properties of a germination-specific cortex-lytic enzyme from spores of Bacillus megaterium KM

Two peptidoglycan-lytic enzyme activities were isolated from spores of Bacillus megaterium KM. Surface-bound lytic enzyme was extracted from dormant spores and hydrolysed a variety of peptidoglycan substrates including isolated spore cortex, but did not cause refractility changes in permeabilized spores. Germination-specific lytic enzyme activity appeared early in germination and had minimal activity on isolated peptidoglycan substrates, but caused refractility changes in permeabilized spores of several Bacillus isolated peptidoglycan substrates, but caused refractility changes in permeabilized spores of several Bacillus species. The germination-specific lytic enzyme was shown to be a heat-sensitive 29 kDa protein with maximal activity at pH 6.5. It catalysed post-commitment muramic acid delta-lactam synthesis and displayed an inhibitor profile similar to that for post-commitment A600 loss. The relationship of the germination-specific enzyme to a recently proposed model of spore germination is discussed.

Isolation and characterization of forespores from Bacillus megaterium

A procedure for isolation of intact forespores from sporulating Bacillus megaterium cells was developed. The cells were digested with lysozyme and made to release free forespores from the protoplasts by disruption of the cytoplasmic membrane with sonication in phosphate buffer containing 10% glycerol. The suitability of the procedure was confirmed by recovery of dipicolinic acid in the isolated forespores and an electron microscopic observation. The fine structure of the forespores prepared at 6 hr (t6) after initiation of sporulation was similar to that of mature spores, except that the cortex layer and primordial cell wall were thinner and the core was larger. The density, determined by density gradient centrifugation, of the forespores isolated at t6, t10, t12, and mature spores was estimated to be 1.2783, 1.2875, 1.2861, and 1.2858, respectively. The isolated forespores at t6 and t8 were extremely heat labile (D80 of 9.5 and 21.5 min, respectively) relative to mature spores (D80 of 277.8 min). These forespores were also less resistant to organic solvents. Germination of the forespores as well as mature spores was induced by KNO3, D-glucose, and L-leucine. Forespores at t6 were more sensitive to KNO3-induced germination than those at t10, t12, and mature spores when measured by reduction in the optical density of cell suspension.

Comparative antigenicity of spore coat proteins from Bacillus species using antibody to spore coat proteins of Bacillus megaterium

Spore coat proteins obtained by extraction with sodium dodecylsulfate/dithiothreitol from six Bacillus spores were compared by immunoblot analysis using antibodies to spore coat proteins from two strains of B. megaterium. Although the extract from spores of each strain had heterogenous proteins with various molecular weights, there were some bands which cross-reacted with specific antibodies from B. megaterium spores. Specific antibody to 48K protein from B. megaterium ATCC 12872 cross-reacted with 17K protein from B. megaterium ATCC 19213, 13K protein from B. cereus and 50K protein from B. subtilis 60015 and B. subtilis NRRL B558. Also, specific antibody to 22K protein from the same strain cross-reacted with 22K and 17K proteins from B. megaterium ATCC 19213 and 13K protein from B. cereus T. Specific antibody to 17K protein from B. megaterium ATCC 19213 reacted with 22K and 19K proteins in addition to 17K protein of own strain, and it was cross-reactive with 16K protein from B. megaterium ATCC 12872, 19K and 27K proteins from B. thiaminolyticus, 13K protein from B. cereus.

Precursor processing during the maturation of a spore-coat protein in Bacillus megaterium KM

A protein of apparent mol.wt. 35000 that is extractable from the purified coat fraction of Bacillus megaterium KM spores is synthesized during sporulation as a precursor protein from which a 12-13 amino acid peptide is removed. Cleavage of this small peptide is delayed until 60-90 min after precursor synthesis and is concomitant with the morphological appearance of stage VI. The addition of chloramphenicol, subsequent to precursor synthesis, prevents the appearance of this late processing event. Two-dimensional non-equilibrium pH-gradient gel electrophoresis of the integument extract of forespores isolated at stage V from sporangia pulse-labelled with L-[35S]methionine 1 h before isolation, revealed both unprocessed and processed components. Similar analysis of total protein from the corresponding mother cells revealed only the unprocessed component in relatively small amounts, suggesting that, although the protein may be synthesized in the mother-cell compartment, processing may be restricted to the forespore. Peptide analysis by limited proteolysis was used to examine the relationship between the 35000- and a 17500-mol.wt. coat protein. The possible implications of limited proteolytic processing to maturation of the spore coat are discussed.