Search for Cry proteins expressed by Bacillus spp. genomes, using hidden Markov model profiles

This report focuses on a systematic search for Cry proteins in Bacillus spp. other than B. thuringiensis by analyzing reported Bacillus spp. genomes, using conserved sequences from the C-terminal half of reported Cry proteins in hidden Markov model profiles. A high-throughput model based on the use of HMMER and CD-HIT tools was designed, which identified Cry proteins. This model was used on 857 reported Bacillus spp. genomes, where 174 Cry protein sequences were identified, mostly, as expected, in B. thuringiensis genomes but, interestingly, 42 were identified on other species. Despite including 89 species of Bacillus in the HMMER analysis, Cry protein sequences were found only in genomes from species within the B. cereus group. According to the species registered at the NCBI database containing each genome, this group was formed by 18 non-B. thuringiensis strains. However, when sequences in those genomes were analyzed by multilocus sequence typing, the number of non-B. thuringiensis strains increased to 39, indicating that as many as 119 Cry protein sequences were found in four non-B. thuringiensis species. Therefore, dispersion of Cry proteins is much wider and frequent than previously thought, questioning its role in nature.