Draft genome comparison of representatives of the three dominant genotype groups of dairy Bacillus licheniformis...

The spore-forming bacterium Bacillus licheniformis is a common contaminant of milk and milk products. Strains of this species isolated from dairy products can be differentiated into three major groups, namely, G, F1, and F2, using random amplification of polymorphic DNA (RAPD) analysis; however, little is known about the genomic differences between these groups and the identity of the fragments that make up their RAPD profiles. In this work we obtained high-quality draft genomes of representative strains from each of the three RAPD groups (designated strain G-1, strain F1-1, and strain F2-1) and compared them to each other and to B. licheniformis ATCC 14580 and Bacillus subtilis 168. Whole-genome comparison and multilocus sequence typing revealed that strain G-1 contains significant sequence variability and belongs to a lineage distinct from the group F strains. Strain G-1 was found to contain genes coding for a type I restriction modification system, urease production, and bacitracin synthesis, as well as the 8-kbp plasmid pFL7, and these genes were not present in strains F1-1 and F2-1. In agreement with this, all isolates of group G, but no group F isolates, were found to possess urease activity and antimicrobial activity against Micrococcus. Identification of RAPD band sequences revealed that differences in the RAPD profiles were due to differences in gene lengths, 3' ends of predicted primer binding sites, or gene presence or absence. This work provides a greater understanding of the phylogenetic and phenotypic differences observed within the B. licheniformis species.