MICROBIAL DIVERSITY OF THE CONTAMINATED SOILS IN KAZAKHSTAN OILFIELDS

Oil and oil products adversely affect both the biodiversity of the microorganisms and the soil function. In oil-contaminated soils, unique bacterial communities develop that are adapted to pollution. In this work, the bacterial structure and diversity of the microbial community have been studied in samples of oil-contaminated soils in Kazakhstan deposits using the Illumina MiSeq sequencer. The results of the study showed that the representatives of the following bacterial phyla dominated in the selected soil samples: Proteobacteria, prevailing in oil-contaminated soils (up to 48%), Actinobacteria (up to 29.33%), Firmicutes (up to 25.74%), Bacteroidetes (up to 33.28 %). The representatives of Planctomycetes, Verrucomicrobia, Chloroflexi (0.76%-4.62%) phyla were found in smaller amounts. All the uncontaminated soils were dominated by Micrococcaceae, Flexibacteraceae, Sphingomonadaceae, Planococcaceae, Flavobacteriaceae families, contaminated ones – by Halomonadaceae, Flavobacteriaceae, Alteromonadaceae, Dietziaceae, Pseudomonadaceae, Bacillaceae, Xanthomonadaceae, Anaerolinaceae, Mycobacteriaceae and Peptococcaceae families. At the genus level, samples of uncontaminated and contaminated soils also demonstrated significant diversity. The dominant bacterial genera in the samples of the uncontaminated soil were Hymenobacter, Arthrobacter, Gillisia. In contaminated soils of three deposits the microorganisms of the Halomonas, Marinobacter, Pseudomonas (mostly in 2KO soil sample), Bellilinea and Mycobacterium (mostly Md sample) genera were spread more widely; and a very large population of the microorganisms of the Halomonas genus was found in the contaminated soil sample from the Atyrau region. A comparison of the taxonomic structure of microbial communities of oil-contaminated soils indicates that the composition of the microbial population changes depending on the degree of oil pollution. Samples of uncontaminated background soils were characterized by higher bacterial diversity than samples of contaminated soils. The microorganisms belonging to the dominant phyla were mostly associated with the decomposition of oil hydrocarbons. The characterization of the bacterial communities living in the contaminated soils and the assessment of their ability to decompose oil can potentially be a guide for bioremediation of contaminated soils.