Metagenomic analysis of bacterial community richness and diversity in Belgrade Sava River alluvial aquifers

Abstract

Background: River aquifers are populated by a vast diversity of microorganisms and groundwater quality can be influenced by microbiological processes, while biological activity of bacteria can serve as an ecosystem status indicator and biological generated corrosion and fouling may have a direct impact on aquifer ageing. Objectives: This study aimed to: characterize and evaluate the spatial dynamics and changes of the total bacterial communities; determine whether these changes could be linked to variations of environmental conditions; and sensitivity of various sources of pollutants and undesirable bacteria. Methods: In this study, eleven Belgrade Sava river alluvial aquifers and one piezometer were investigated, using 16S rDNA 454 Life Sciences GSFLX Titanium sequencing. Results: Generally, more than 26 bacterial phyla with 395 of different bacterial taxa were revealed. Shannon, Simpson and Chao1 indices confirmed that the bacterial diversity was high but significantly varied between aquifers. The richest biodiversity in bacterial taxa was noted in aquifers RB-5m, RB15-1, RB-38 and RB-48, with the frequent presence of sulfur compounds oxidizers and nitrate reducers. Principal coordinate analysis showed that aquifers RB-13 and RB-16 were phylogenetically the most distant among all aquifers, with more than 47% of variability, the lowest number of bacterial taxa and the highest percent of facultative anaerobes. Site series investigation along the alluvial aquifers also highlighted habitat specialization for some major members of the community (genus Thiobacillus). It can be assumed that the low content of oxygen and organic carbon favours species that could use iron, sulphides and/or nitrates compounds in their metabolism.