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Research shows that occupational exposure to Bacillus thuringiensis poses a health hazard to greenhouse workers as shown by the isolation of B. thuringiensis in the fecal matter. However, fecal occurrence of the bacterium does not show any correlation with the gastrointestinal symptoms.

A comparison of the conjugation systems of F plasmid from Escherichia coli and plasmid pCF10 from Enterococcus faecalis using data from the aggregation-mediated conjugation system encoded from Bacillus thuringiensis' pXO16 reveals a number of common characteristics despite the obvious basic differences. One common characteristic shared by the two plasmids include their ability to sustain highly efficient conjugative transfers in a liquid environment.

The plasmid pAW63, the minor plasmid of the two large plasmids of Bacillus thuringiensis subspecies kurstaki strain HD73 was shown to be self-transmissible. Further, it can be transmitted to the other species of the genus Bacillus. The plasmid was tagged with the tetracycline resistance gene and was observed to be transmitted to all recipients within two hours. Bacillus thuringiensis subspecies kurstaki strain HD73 colonizes the larvae of lepidopterans.

Analysis of the plasmid contents of various B. thurigiensis subsp. israelensis isolates, aggregation mutants, plasmid-cured derivatives, transconjugants and recured transconsjugants showed that the Agr+ phenotype and Agr- of B. thuringiensis subsp. israelensis are correlated with the presence of plasmid pXO16. The evidence of this fact is presented.

Gene mobilization in small plasmids is related to specific aggregation of donor and receptor cells for the genus bacillus. A shuttle vector pAND006 containing the replication gene rep14-3 from a small plasmid pTX14-3 and it origin of replication, are mobilized and compared to the mobilization gene-containing small plasmid pBC16. PTX14-3 and pBC16 are part of the ten plasmids contained in the Bacillus thuringiensis subspecies israelensis.

Abstract Background Bacillus cereus, Bacillus anthracis and Bacillus thuringiensis belong to the genetically close-knit Bacillus cereus sensu lato group, a family of rod-shaped Gram-positive bacteria. pAW63 is the first conjugative plasmid from the B. cereus group to be completely sequenced. Results The 71,777 bp nucleotide sequence of pAW63 reveals a modular structure, including a 42 kb tra region encoding homologs of the Type IV secretion systems components VirB11, VirB4 and VirD4, as well as homologs of Gram-positive conjugation genes from Enterococcus, Lactococcus, Listeria, Streptococcus and Staphylococcus species. It also firmly establishes the existence of a common backbone between pAW63, pXO2 from Bacillus anthracis and pBT9727 from the pathogenic Bacillus thuringiensis serovar konkukian strain 97-27. The alignment of these three plasmids highlights the presence of well conserved segments, in contrast to distinct regions of high sequence plasticity. The study of their specific differences has provided a three-point reference framework that can be exploited to formulate solid hypotheses concerning the functionalities and the molecular evolution of these three closely related plasmids. This has provided insight into the chronology of their divergence, and led to the discovery of two Type II introns on pAW63, matching copies of the mobile element IS231L in different loci of pXO2 and pBT9727, and the identification on pXO2 of a 37 kb pathogenicity island (PAI) containing the anthrax capsule genes. Conclusion The complete sequence determination of pAW63 has led to a functional map of the plasmid yielding insights into its conjugative apparatus, which includes T4SS-like components, as well as its resemblance to other large plasmids of Gram-positive bacteria. Of particular interest is the extensive homology shared between pAW63 and pXO2, the second virulence plasmid of B. anthracis, as well as pBT9727 from the pathogenic strain B. thuringiensis serovar konkukian strain 97-27.

A detailed functional analysis of pG12, a 9672 bp plasmid from Bacillus thuringiensis H1.1 that harbors the 4149 bp transposon Tn4430, was conducted. The experiment included its double-strand and single-strand replication module, the activity of its Mob proteins and the influence of various modules on its segregational stability. The distribution of the pG12 replicon among members of the Bacillus cereus group was also investigated.

The presence of the B component of hemolysin BL (hblA), enterotoxin BceT (bceT), and enterotoxin S (entS) genes in mosquito-larvicidal Bacillus sp., including 25 B. sphaericus and 4 B. thuringiensis subsp. israelensis strains, has been analyzed by multiplex PCR in this study. The results showed that all four B. thuringiensis strains contain the hblA gene and the sequences of bceT and entS genes. However, none of the enterotoxin gene sequences were detected in the B. sphaericus strains. The enterotoxin production in all strains has also been analyzed by using two commercial immunoassay kits (TECRA and RPLA), and it has been proved that all the B. thuringiensis strains and one B. cereus strain can produce enterotoxins during growth. No enterotoxin activity could be detected in B. sphaericus strains. [ABSTRACT FROM AUTHOR]

Abstract: The impacts of growth media and temperature on production of cereulide, the emetic toxin of Bacillus cereus, were measured for seven well characterised strains selected for diversity of biochemical and genetic properties and sources of origin. All strains carried cereulide synthase gene, ces, on a megaplasmid of ca. 200 kb and all grew up to 48–50 °C, but produced cereulide only up to 39 °C. On tryptic soy agar five strains, originating from foods, food poisonings and environment, produced highest amounts of cereulide at 23 to 28 °C, whereas two strains, from human faeces, produced cereulide similarly from 23 to 39 °C, with no clear temperature trend. These two strains differed from the others also by producing more cereulide on tryptic soy agar if supplemented with 5 vol.% of blood, whereas the other five strains produced similarly, independent on the presence of blood. On oatmeal agar only one strain produced major amounts of cereulide. On skim milk agar, raw milk agar, and MacConkey agar most strains grew well but produced only low amounts of cereulide. Three media components, the ratio [K+]:[Na+], contents of glycine and [Na+], appeared of significance for predicting cereulide production. Increase of [K+]:[Na+] (focal variable) predicted (P <0.001) high cereulide provided that the contents of glycine and [Na+] (additional variables) were kept constant. The results show that growth medium and temperature up and downregulate cereulide production by emetic B. cereus in a complex manner. The relevance of the findings to production of cereulide in the gut and to the safety of amino acids as additives in foods containing live toxinogenic organisms is discussed. [Copyright &y& Elsevier]