Mercury-Resistant Bacteria from Permafrost Sediments and Prospects for their Use in Comparative Studies of Mercury Resistance Determinants

Mercury-resistant bacteria were isolated from permafrost sediments of Kolyma lowland and Canada existing over five thousand to two million years. Their content was shown to vary within the range 0.001–2.9% and to depend on the amount of mercury in sampling sites (coefficient of correlation 0.75). A collection of mercury-resistant bacterial strains was created. In this collection, various representatives of both Gram-positive bacteria (Bacillus, Exiguobacterium, Micrococcus, Arthrobacter) and Gram-negative bacteria (Pseudomonas, Acinetobacter, Plesiomonas, Myxobacteriales) were identified. Most resistant bacteria were found to contain determinants homologous to mer-operons of contemporary bacteria. The isolated strains of paleobacteria are proposed to be used for a comparative structural study of contemporary and ancient plasmids and transposons carrying mercury resistance determinants.