Genome structure in the vole bacillus, Mycobacterium microti, a member of the Mycobacterium tuberculosis complex with a low virulence for humans

Open Access
Publisher Website
Google Scholar
Abstract
Mycobacterium microti, a member of theMycobacterium tuberculosiscomplex, is phylogenetically closely related toM. tuberculosis, differing in a few biochemical properties. However, these species have different levels of virulence in different hosts; most notablyM. microtishows lower virulence for humans thanM. tuberculosis. This report presents genomic comparisons using DNA microarray analysis for an extensive study of the diversity ofM. microtistrains. Compared toM. tuberculosisH37Rv, 13 deletions were identified in 12 strains ofM. microti, including the regions RD1 to RD10, which are also missing inMycobacterium bovisBCG. In addition, four new deleted regions, named MiD1, RD1β, MiD2 and MiD3, were identified. DNA sequencing was used to define the extent of most of the deletions in one strain. Although RD1 ofM. bovisBCG andM. microtiis thought to be crucial for attenuation, in this study, three of the fourM. microtistrains that were isolated from immunocompetent patients had the RD1 deletion. In fact, only the RD3 deletion was present in all of the strains examined, although deletions RD7, RD8 and MiD1 were found in almost all theM. microtistrains. These deletions might therefore have some relation to the different host range ofM. microti. It was also noticeable that of the 12 strains studied, only three were identical; these strains were all isolated from immunocompetent humans, suggesting that they could have arisen from a single source. Thus, this study shows that it is difficult to ascribe virulence to any particular pattern of deletion inM. microti.