Mapping of Antibiotic Resistance Markers in Mycobacterium smegmatis

Abstract

Linkage relationships among loci conferring resistances to neomycin-kanamycin (nek), viomycin-capreomycin (vic) and streptomycin (str), as well as auxotrophic markers, were analyzed employing the conjugation system of Mycobacterium smegmatis strains Rabinowitchi and PM5. Nek and vic loci were found to be closely linked to each other and also linked to argA-6 and argB-1. No linkage was observed between str and nek or vic. The locations of other loci, met-5, his-13 and leu-11, also could not be determined.In certain recombinant types, nek and vic alleles formed stable heterogenotes. When nekr and neks or vicr and vics alleles existed in one cell, sensitivity to those drugs was dominant over resistance. Segregants of nekr or vicr from the heterogenotes were detected at a frequency of about 10-4 to 10-5. Such a stable heterogenote was not detected in str allele.

Interactions between Viomycin Resistance and Streptomycin Resistance on Ribosomes of Mycobacterium smegmatis

“…This indicates that, in addition to the streptomycin resistant mutation, the 30 S subunit of ACP-2 has an altered component which is indispensable for modification of viomycin resistance. 2), it appears that several ribosomal genes of strain ATCC 14468 are located close to argB in a gene cluster as found in strain Rabinowitch (8,15). However, we do not know the relationships among the genetic loci of strain Rabinowitch (especially the vicA gene which determines a 50 S component) and the loci discussed in the present paper.…”

“…Resistance to viomycin, capreomycin, and tuberactinomycin of AC-13 is located on the 50 S ribosomal subunits and streptomycin resistance is due to an alteration of the 30 S subunits (20,21). Since genes vicA and vicB confer resistance to both viomycin and capreomycin (8,15), and complete cross resistance was observed between viomycin and tuberactinomycin (6,12), it was assumed that vic alleles also conferred resistance to tuberactinomycin. To understand the reason ET Table 5.…”

Multiple Mating Types of Mycobacterium smegmatis

“…All of the strains except SN 2 and ATCC 14468 had been maintained for more than 10 years in this laboratory. Auxotrophic mutant substrains and streptomycin (SM)-resistant substrains were isolated from strains Jucho ( J), Takeuchi (T), Rabinowitchi (R), Lacticola (L), ATCC 607 (F), PM 5 (P), and Nishi 1 (N) by the method described previously [12] lowing procedure. Colonies obtained from cultures treated with acridine dye, sodium dodecyl sulfate (SDS) or a higher temperature (45 C) were replicated on complete agar plates which had been seeded with compatible tester strain.…”

“…However, linkage relationships among most of the markers were impossible to detect because of the ordering ambiguity [15]. One exception was found for the markers of arginine biosynthesis and certain genes conferring drug resistance [7,12]. Employing R-46 and P-31, and R-28 and P-17, therefore, experiments were carried out to see whether the genes controlling mating were closely linked to the chromosomal markers ( argB , leu, his, str, , nek) .…”

“…These facts appeared to be explained by assuming that there might be two groups of strains of M. smegmatis, male and female, which were compatible with each other (Lacticola and Rabinowitchi groups as male and Jucho and PM 5 groups as female). Using these systems, however, no linkage map could be constructed for most of the markers tested because of the ordering ambiguity [15], except that a close linkage was demonstrated for certain markers including those of drug resistance [7,12]. Attempts to find new conjugation systems in mycobacteria other than those described above, with the aim of drawing the genetic map of mycobacteria, indicated that there are many conjugation systems among M. smegmatis strains, but we failed to demonstrate genetic interactions in the other species including Mycobacterium phlei, Mycobacterium tuberculosis and Mycobacterium bovis.…”