Most importantly, it raises the question that, if one wishes to apply modern principles of phylogenetic systematics, where and how does one ‘draw the line’ in the attempt to delineate a novel species of Bacillus. Recently, it has been suggested that the use of multilocus sequence analysis should be investigated as a means to detect and define novel species of bacteria. The purpose of this study was to investigate the use of multilocus phylogenetic analysis as a tool to detect novel taxa within the B. subtilis species complex, which has become a model system for the study of bacterial speciation.