Characterization of a Mycobacterium bovis BCG insertion sequence related to the IS21 family

The structure and distribution of a Mycobacterium bovis BCG insertion eleme nt of the IS21 family were investigated. Several IS21-like elements found i n mycobacterial genomes were separated in four types, following their nucle ic acid similarities. The M. bovis BCG IS21 element is highly similar to IS 1533 (class I), 70% similar to IS1534 (class II), 52% similar to IS1532 (cl ass III) of Mycobacterium tuberculosis, and 54% similar to both an Mycobact erium avium serovar 2 and an M. avium silvaticum IS (class IV). The M bovis BCG IS21 element of the class I appears to be present in a single copy in the genome of M I. bovis BCG, M. bovis, M. tuberculosis and Mycobacterium a fricanum and to be absent from all other tested species of the Corynebacter ia-Mycobacteria-Nocardia group. (C) 1999 Federation of European Microbiolog ical Societies. Published by Elsevier Science B.V. All rights reserved.