Molecular profiling of microbial population dynamics in environmental water
Increasing socio-economic growth and development of South Africa’s freshwater systems require continuous augmentation of water sources to meet the growing water requirements of communities and industries. Anthropogenic disturbances have caused the water quality of many freshwater systems to drastically deteriorate due to constant disposal of domestic, industrial, and agricultural waste into surface waters. Government agencies make use of biomonitoring programmes to effectively manage the countries’ freshwater resources. These programmes use a variety of biological indicators (e.g., macroinvertebrates, fish, diatoms and algal species) and physico-chemical variables to determine the state of the environment. However, attempts to use microbial community structures as bioindicators of anthropogenic perturbations are greatly neglected. This study used molecular techniques (PCR-DGGE and 454-pyrosequencing) and multivariate analysis to develop a robust monitoring technique to determine the impacts of environmental disturbances on bacterial community compositions in river systems in the North West Province. Significant contributions made by this project included the establishment of a bacterial diversity framework for South African freshwater systems that are impacted by a variety of anthropogenic activities (e.g., urban and informal settlements, agriculture and mining). Furthermore, case studies demonstrated the prevalence of specific taxa at polluted sites, as well as positive and negative associations between taxa and environmental variables and pollutants. Finally, biogeochemical cycles could be partially matched to bacterial community structures in river systems. The first part of the project included a pilot study that investigated bacterial structures in a segment of the Vaal River in response to environmental parameters using molecular techniques and multivariate analysis. The most important observations made during this study included the generation of a larger bacterial diversity dataset by pyrosequencing compared to PCR-DGGE. In addition, metagenomic and multivariate analyses provided clues about potential biogeochemical roles of different taxa. The second and third part of the project included two case studies that investigated bacterial communities in the Mooi River and Wonderfonteinspruit in response to environmental activities. Both these systems are impacted by a variety of external sources such as urban and informal settlements, agriculture, and mining. The results demonstrated that perturbations nearby the Mooi River and Wonderfonteinspruit caused the overall water quality to deteriorate which in turn had a profound impact on bacterial community composition. Bacterial community structures at reference/control sites (Muiskraal and Turffontein dolomitic eye) had overall high species diversity (richness and evenness), whereas polluted sites showed lower species diversity and were dominated by the Beta- and Gammaproteobacteria, Bacteroidetes, and Verrucomicrobia. In addition, various potential pathogens (e.g. Eschirichia/Shigella, Legionella, Staphylococcus, Streptococcus etc.) were identified at impacted sites. Multivariate analysis suggested that bacterial communities and certain taxa (Malikia, Algoriphagus, Rhodobacter, Brevundimonas and Sphingopyxis) at polluted sites were mainly impacted by temperature, pH, nutrient levels, and heavy metals. Finally, the proportion of nitrogen and sulphur bacteria corresponded well with the nitrogen and sulphur levels measured in the Wonderfonteinspruit. Based on these results, it was concluded that bacterial community structures might provide a good indicator of anthropogenic disturbances in freshwater systems and may be incorporated into biomonitoring programs.