Five recombinant plasmids, pBK2646, pBK611, pRC3, pRC4 and pRC5, carrying rpoB rifampicin-resistant RNA-polymerase genes were obtained. The sequence analysis of these plasmids revealed certain structural changes in the rpoB gene which specify corresponding alterations in the beta-subunit of RNA polymerase. Some functional properties of the corresponding mutant strains and their RNA polymerases have been investigated.

Most bacterial cells (Pseudomonas, Acinetobacter) obtained from the soil at the Khaidarkan mercury and antimony mine (Kirghiz USSR) contain R plasmids with mercury (HgCl2) resistance determinants. The plasmids have a large molecular mass (about 100 MD, though smaller ones also occur), and at least some of them are transmissive. Many of the Hgr bacteria also display an elevated antimony (SbCl3) resistance, though this trait was not shown to be plasmid-dependent. There are practically no Hgr plasmids in bacteria taken from the soil at different distances from the mine: the saturation of bacteria with Hgr plasmids is maintained by selective pressure only in the area with a high enough toxin concentration. In the same mercury and antimony deposit area Hgr plasmids were also found in Escherichia coli isolates from the gut of Mus musculus mice and Bufo viridis toads. At least some of the bacterial plasmids obtained from animals also carry antibiotic-resistance determinants (Tcr, Cmr, Smr). These plasmids are also transmissive. They display internal instability and lose their resistance determinants after a conjugation transfer to other E. coli strains.

The deficiency of the 38B-40 region containing histone genes in one of the 2nd chromosomes of D. melanogaster triploid intersexes increases the template activity of X-chromosomes both in vivo and in vitro without noticeably affecting autosome activity. This deficiency in the heterozygous state inhibits the variegated position effect of the white gene in the T(1;3)Wvco translocation in diploid females and males, but not affect their rate of development. The variegation suppressor Su(var)hg-1 not only suppress the gene position effect in diploid flies, but also increases the template activity of X-chromosomes in triploid intersexes. The results are discussed with respect to the dependence of gene activity on the structure of chromosomes (density of DNP packing).

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