The genome, evolution and diversity of Mycobacterium ulcerans

Mycobacterium ulcerans (M. ulcerans) causes a devastating infection of the skin and underlying tissue commonly known as Buruli ulcer (BU). Genetic analyses indicate that M. ulcerans has a common ancestor with Mycobacterium marinum (M. marinum) and has diverged from this fish and human pathogen perhaps around a million years ago. M. ulcerans is characterized by minimal genetic diversity and since it has a highly clonal population structure, genetic differences between individual isolates reflect changes that have occurred sequentially from their respective progenitors. This feature, which is shared by other bacterial pathogens with low sequence diversity, such as Yersinia pestis and Bordetella pertussis renders M. ulcerans a promising model to reveal evolutionary mechanisms. Until today transmission pathways and environmental reservoirs of M. ulcerans are not entirely explored. However, comparative genome analysis of closely related M. ulcerans isolates is anticipated to give deeper insights into the population structure of this enigmatic mycobacterium.

► We review genome, evolution and genetic diversity of Mycobacterium ulcerans. ► Evolution is dominated by acquisition of a virulence plasmid. ► Extensive genome downsizing and pseudogene formation is ongoing. ► Limited genetic diversity and a clonal population structure are hallmarks.