Subtyping of Bacillus cereus by total cell protein patterns and arbitrary primer polymerase chain reaction

Changes in numbers and kinds of bacteria during a chickpea submerged fermentation used as a leavening agent for bread production

The microflora developed during a submerged fermentation of coarsely ground chickpea (Cicer arietinum L.) in water (primary starter) and during raising a dough from wheat flour (adapted starter) was studied. In the fermenting liquid, only populations of Bacillus and Clostridium developed. Bacilli increased their loads significantly (p<0.05) during fermentation for 8-12 h and then remained constant. Clostridia developed (p<0.05) subsequently to levels of 10(7) cfu/ml at 18 h, when the pH of the fermenting liquid had decreased (p<0.05) to approximately 5.4. It also seems that the rise of the adapted starter within 2 h was caused by enzymes present in the primary starter and those liberated after cell death by the declining populations of bacilli and clostridia. The principal groups of isolates in all fermentation experiments (with chickpea seeds from five different areas) seemed to have the phenotypic characteristics of Bacillus cereus group and Clostridium perfringens. SDS-PAGE of whole-cell proteins elucidated the taxonomic position of the B. cereus group of strains as B. cereus and Bacillus thuringiensis and confirmed the phenotypic allocation of C. perfringens isolates. Strains phenotypically characterized as Bacillus licheniformis and Clostridium beijerinckii were also found to belong to these same species by SDS-PAGE. In addition, results showed that the fermenting broth was not toxic to mice when inoculated intraperitoneally and the product can thus be considered as safe for consumption.

Production and characterization of monoclonal antibodies against vegetative cells of Bacillus cereus

Two monoclonal antibodies (MAbs) against Bacillus cereus were produced. The MAbs (8D3 and 9B7) were selected by enzyme-linked immunosorbent assay for their reactivity with B. cereus vegetative cells. They reacted with B. cereus vegetative cells while failing to recognize B. cereus spores. Immunoblotting revealed that MAb 8D3 recognized a 22-kDa antigen, while MAb 9B7 recognized two antigens with molecular masses of approximately 58 and 62 kDa. The use of MAbs 8D3 and 9B7 in combination to develop an immunological method for the detection of B. cereus vegetative cells in foods was investigated.

Cloning of the nprA gene for neutral protease A of Bacillus thuringiensis and effect of in vivo deletion of nprA on insecticidal crystal protein

The nprA gene, encoding Bacillus thuringiensis neutral protease A, was cloned by the use of gene-specific oligonucleotides. The size of neutral protease A deduced from the nprA sequence was 566 amino acids (60,982 Da). The cloned nprA gene was partially deleted in vitro, and the deleted allele, designated nprA3, was used to construct an nprA3 strain (neutral protease A-deficient strain) of B. thuringiensis. Growth and sporulation of the nprA3 strain were similar to those of an isogenic nprA+ strain, although the extracellular proteolytic activity of the nprA3 strain was significantly less than that of the nprA+ strain. The nprA3 strain produced insecticidal crystal proteins that were more stable than those of the isogenic nprA+ strain after solubilization in vitro, and sporulated cultures of the nprA3 strain contained higher concentrations of full-length insecticidal crystal proteins than did those of its isogenic counterpart. The absence of neutral protease A did not affect the insecticidal activity of a lepidopteran-specific crystal protein of B. thuringiensis. These results indicate that crystal protein stability and yield may be improved by deletion of specific proteases from B. thuringiensis.