An avirulent strain derived from its virulent parent strain H37. Mycobacterium tuberculosis H37Ra strain:ATCC25177

Mycobacterium tuberculosis H37Ra. This strain (H37Ra; ATCC 25177) is an avirulent strain derived from its virulent parent strain H37 (isolated from a 19 year-old male patient with chronic pulmonary tuberculosis by Edward R. Baldwin in 1905) through a process of aging and dissociation from in vitro culture in 1935. H37Ra has several different characteristics compared with its virulent sister strain H37Rv, including a rough, raised colony morphology, loss of cord formation, loss of neutral red dye binding, decreased ability to survive under anaerobic conditions, reduced ability to survive inside macrophages, and loss of virulence in guinea pigs, mice and rabbits. Despite numerous studies in the past 70 years, the molecular basis for the loss of virulence in H37Ra has remained obscure. In this project, we determined the whole genome sequence for the H37Ra strain from ATCC (ATCC 25177). The choice of the ATCC type strain of H37Ra is important as repeated in vitro culture is known to create changes in the genome. Determination of the genome sequence of H37Ra and comparative genome analysis of H37Ra with the recently sequenced virulent sister strain H37Rv is of critical importance not only for elucidating the mechanism of attenuation of virulence in H37Ra but also for understanding the virulence and pathogenesis of M. tuberculosis.