Inhibition of growth and cell wall synthesis of Mycobacterium smegmatis by d-threonine

Gene manipulation in mycobacteria

Gene manipulation in mycobacteria developed in two phases. In the first phase genes of mycobacteria were transferred into cells of E. coli and Streptomyces lividans. In the second phase, heterologous genes were transferred into mycobacteria either with a shuttle plasmid or hybrid plasmids. A prerequisite for successful gene manipulation in mycobacteria was a thorough understanding of plasmids in mycobacteria. Construction of recombinant DNA molecules contributed not only to the fact that mycobacteria did not remain outside the mainstream of modern genetic research but also to their present practical importance.

Spheroplast formation of Mycobacterium smegmatis and morphological aspects of their reversion to the bacillary form

Cell wall-deficient forms (spheroplasts) of Mycobacterium smegmatis strain P53 were prepared by combined treatment with glycine, lysozyme, and lytic enzyme no. 2 as the spheroplasting agents. Quantitative mass conversion to spherical forms was effected by pretreatment of the intact cells with 1.2% glycine in nutrient broth, followed by transfer to spheroplasting medium containing the above agents. Two apparent modes of reversion to the bacillary form were observed under electron microscopy. The first one was initiated by budding from the spheroplasts. The buds gradually elongated to become the mycelial form, which showed branching, septation, and fragmentation. The second resulted from the intracellular formation of tiny cells, possibly the elementary bodies, and their release from the spheroplasts.