Diversity and functional profile of bacterial communities at Lancaster acid mine drainage dam, South Africa as revealed by 16S rRNA gene high-throughput sequencing analysis

Thabile Lukhele, Ramganesh Selvarajan, Hlengilizwe Nyoni, Bheki Brilliance Mamba, Titus Alfred Makudali Msagati

This study surveyed physicochemical properties and bacterial community structure of water and sediments from an acid mine drainage (AMD) dam in South Africa. High-throughput sequence analysis revealed low diversity bacterial communities affiliated within 8 dominant phyla; Acidobacteria, Actinobacteria, Chloroflexi, Firmicutes, Nitrospirae, Proteobacteria, Saccharibacteria, and ca. TM6_(Dependentiae). Acidiphilium spp. which are common AMD inhabitants but rarely occur as dominant taxa, were the most abundant in both AMD water and sediments. Other groups making up the community are less common AMD inhabitants; Acidibacillus, Acidibacter, Acidobacterium, Acidothermus, Legionella, Metallibacterium, Mycobacterium, as well as elusive taxa (Saccharibacteria, ca. TM6_(Dependentiae) and ca. JG37-AG-4). Although most of the taxa are shared between sediment and water communities, alpha diversity indices indicate a higher species richness in the sediments. From canonical correspondence analysis, DOC, Mn, Cu, Cr, Al, Fe, Ca were identified as important determinants of community structure in water, compared to DOC, Ca, Cu, Fe, Zn, Mg, K, Mn, Al, sulfates, and nitrates in sediments. Predictive functional profiling recovered genes associated with bacterial growth and those related to survival and adaptation to the harsh environmental conditions. Overall, the study reports on a distinct AMD bacterial community and highlights sediments as microhabitats with higher species richness than water.