Abstract
An investigation into the presence of plasmids in Mycobacterium tuberculosis was conducted. No extrachromosomal DNA was found although some evidence for their presence were detected. Plasmid-related sequences were however found in the genomic DNA of M, tuberculosis. Isolation of plasmid-related sequences from a strain of M, tuberculosis resulted in two different DNA probes which showed high specificity for M, tuberculosis and related species. One of these probes gave banding patterns which suggest the presence of restriction fragment polymorphism in M, tuberculosis. The other probe gave banding patterns which were unique for each strain tested. The use of these probes for epidemiological studies is suggested. An E. coli plasmid, pIJ666, was successfully introduced into Mycobacterium smegmatis ATCC607 and stably maintained through several subcultures. One of the selective markers, a chloramphenicol resistance gene from Tn9, was efficiently expressed in M. smegmatis ATCC607. The development of a transformation system in M. smegmatis from this initial study is indicated.