Bacillus subtilis is the best-characterized member of the Gram-positive bacteria. Its genome of 4,214,810 base pairs comprises 4,100 protein-coding genes. Of these protein-coding genes, 53% are represented once, while a quarter of the genome corresponds to several gene families that have been greatly expanded by gene duplication, the largest family containing 77 putative ATP-binding transport proteins. In addition, a large proportion of the genetic capacity is devoted to the utilization of a variety of carbon sources, including many plant-derived molecules. The identification of five signal peptidase genes, as well as several genes for components of the secretion apparatus, is important given the capacity of Bacillus strains to secrete large amounts of industrially important enzymes. Many of the genes are involved in the synthesis of secondary metabolites, including antibiotics, that are more typically associated with Streptomyces species. The genome contains at least ten prophages or remnants of prophages, indicating that bacteriophage infection has played an important evolutionary role in horizontal gene transfer, in particular in the propagation of bacterial pathogenesis.

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A .M . P R ES CO T T A ND C .R . F R IC KE R . 1999. In situ hybridization experiments with oligonucleotide probes directed against the 16S and 18S rRNA molecules have been used successfully to identify specific organisms in mixed microbial populations. However, there are limitations in applying these techniques to environmental samples. In the present study we have examined the possibility of using in situ reverse transcription as an alternative to hybridization methods for the rapid detection of Escherichia coli and the waterborne parasite Cryptosporidium parvum. Following fixation and permeabilization of the cells,extension reactions were performed with species-specific primers, AMV reverse transcriptase and either cy3-AP3-dUTP or fluorescein-11-dUTP at 45°C for 45 min. The cells or oocysts were then filtered onto Costar metallic membrane filters and images captured with a CCD camera. The results have shown that this technique can successfully detect E. coli cells and C. parvum oocysts in under 2 h.