Mycobacterium brisbanense is a member of Mycobacterium fortuitum third biovariant complex, which includes rapidly growing Mycobacterium spp. that normally inhabit soil, dust and water, and can sometimes cause respiratory tract infections in humans. We present the first whole-genome analysis of M. brisbanense UM_WWY which was isolated from a 70-year-old Malaysian patient. Molecular phylogenetic analyses confirmed the identification of this strain as M. brisbanense and showed that it has an unusually large genome compared with related mycobacteria. The large genome size of M. brisbanense UM_WWY (~7.7Mbp) is consistent with further findings that this strain has a highly variable genome structure that contains many putative horizontally transferred genomic islands and prophage. Comparative analysis showed that M. brisbanense UM_WWY is the only Mycobacterium species that possesses a complete set of genes encoding enzymes involved in the urea cycle, suggesting that this soil bacterium is able to synthesize urea for use as plant fertilizers. It is likely that M. brisbanense UM_WWY is adapted to live in soil as its primary habitat since the genome contains many genes associated with nitrogen metabolism. Nevertheless, a large number of predicted virulence genes were identified in M. brisbanense UM_WWY that are mostly shared with well-studied mycobacterial pathogens such as Mycobacterium tuberculosis and Mycobacterium abscessus. These findings are consistent with the role of M. brisbanense as an opportunistic pathogen of humans. The whole-genome study of UM_WWY has provided the basis for future work of M. brisbanense.
Mycobacteria a genus of Actinobacteria are widespread in nature ranging from soil-dwelling saprophytes to human and animal pathogens. The rate of growth has been a classifying factor for the Mycobacterium spp., dividing them into the rapid growers and the slow growers. Here we have performed a comparative genome study of mycobacterial species in order to get better understanding of their evolution, particularly to understand the distinction between the rapid and slow growers. Our study shows that the slow growers had generally gained and lost more genes compared to the rapid growers. The slow growers might haved eventually lost genes (LivFGMH operon, shaACDEFG genes and MspA porin) that could contribute to the slow growth rate of the slow growers. The genes gained and lost in mycobacteria had eventually helped these bacteria to adapt to different environments and have led to the evolution of the present day rapid and slow growers. Our results also show high number of Mycobacterium abscessus specific genes (811 genes) and some of them are associated with the known bacterial quorum sensing genes that might be important for Mycobacterium abscessus to adapt and survive in variety of unfavorable environments. Mycobacterium abscessus also does not contains genes involved in the bacterial defense system and together with the quorum sensing genes may have contributed to the high gene gain rate of Mycobacterium abscessus.