Possibilities of the conjugation process in mycobacteria

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.

Mycobacteria in the light of modern genetics development

It is generally assumed that genetic research of mycobacteria is delayed as compared with other, more commonly used, bacterial models, particularly in the field of genetic transfers. In the field of mutagenesis the problems have been studied to such an extent that replication maps of the chromosome of M. phlei and M. tuberculosis H37 Rv have already been constructed and a new model of the cell cycle of bacteria exhibiting a slow growth rate has been worked out. When the problems of mycobacterial genetics are looked upon in the light of gene manipulations it may be concluded that mycobacteria belong to a few models whose genes are used for cloning and that problems of practical significance will be studied by means of the most modern approaches.

Restriction endonuclease mapping and cloning of Mycobacterium fortuitum var. fortuitum plasmid pAL5000

A restriction map of Mycobacterium fortuitum var. fortuitum plasmid pAL5000 was established. The unique sites for ApaI, BamHI, BglII, BstEII, ClaI, EcoRI, EcoRV, HpaI, KpnI and NarI were located on the 5.0-Kb plasmid. The plasmid had no sites for AhaIII, BclI, HindIII, PstI, SphI and XbaI. pAL5000 was cloned into pBR322 and propagated in Escherichia coli. Three hybrid pAL5000-pBR322 plasmids carrying the complete pAL5000 sequence were constructed by joining the plasmids at their BamHI, EcoRI or EcoRV sites. We also cloned into these plasmids a 1489-bp DNA fragment conferring resistance to kanamycin and originating from the streptococcal plasmid pJH1. The construction of these plasmids will facilitate the analysis and manipulation of pAL5000, and may allow the development of a vector system for genetic analysis in mycobacteria.

Genetic effects of N-methyl-N'-nitro-N-nitrosoguanidine and its homologs

Since the discovery of the mutagenic activity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in 1960, this compound has become one of the most widely used chemical mutagens. The present paper gives a survey on the chemistry, metabolism, and mode of interaction of MNNG with DNA and proteins, and of the genotoxic effects of this agent on microorganisms, plants, and animals, including human cells cultured in vitro. Data on the carcinogenicity and teratogenicity of MNNG as well as on the genotoxic effects of homologs of MNNG are also presented.

Recent European research activities in mycobacteriology

The subject of mycobacteriology is becoming an increasingly popular and complex one and the contribution by European scientists has been considerable. The important areas of research include taxonomy and the improvement of identification methods; biochemistry, including enzymology, metabolic regulation, lipid chemistry, iron uptake and metabolism, pigment synthesis and DNA chemistry; genetics and bacteriophages; ecology, including the effect of contact with environmental mycobacteria on the mammalian immune response; immunology; and the association of disease and cell-wall-free mycobacteria and studies on the leprosy bacillus. The European Society of Mycobacteriologists has recently been founded to unite workers in these disciplines and to promote and disseminate knowledge in this subject.