Bacterial Diversity in Heavy Metal Poluted Soil Explored via 16S rRNA Gene Molecular-Genetic Analysis

Bacterial diversity in a xenobiotic polluted soil sample called KCM B was investigated using the 16S rRNA gene approach. The sample was collected from the vicinity of a Pb-Zn (KCM) smelter and pesticides manufacturing plant AGRIA both situated in short distance to each other near the town of Plovdiv, South Bulgaria. MS-ICP analysis showed the sample was moderately contaminated. Only Pb exceeded the EU Maximum Permission Levels (MPL). One clone library was constructed consisting of 150 clones. Our results demonstrated that in the investigated soil bacterial community was dominated by representatives of phylum Proteobacteria (α (28), β (2), γ (40) and δ (2) or in total 72%. Among them the most abundant were γ -Proteobacteria - 40%. Phyla Actinobacteria, Holophaga/Acidobacteria (AHA) and members of AD1 division were detected in an equal amount of 7% each. Bacteria belonging to phyla Cytophaga/Fla¬vobacterium/Bacteroides (CFB) represented 5% of the bacterial community. 2% of the studied clones were affiliated to novel bacteria. In the clone library were detected many unique bacterial fingerprints respective¬ly 16S rDNA sequences. Most of the identified bacterial groups were closely related to bacteria inhabiting other extreme- or xenobiotics polluted environments as uranium mill tailings, metal rich sediments, mine drainages, hydrocarbon contaminated environments, rocks at 300 m under the Ocean floor, deserts and waste water treatment facilities. Great number of recovered sequences in the sample were affiliated to not-yet-cultured bacteria with unknown physiology, morphology or metabolism. Once successfully cultivated these bacteria might be promising for biotransformation of heavy metals and biotechnological application.