Pyrosequencing reveals correlations between extremely acidophilic bacterial communities with hydrogen sulphide concentrations, pH and inert polymer coatings at concrete sewer crown surfaces

Aims: To investigate the acidophilic bacterial communities involved in microbially induced concrete corrosion (MICC). Methods and Results: Our study sites located downstream from a forced main provided a unique opportunity to study the microbial communities involved in MICC under different environmental conditions (gradients of atmospheric H2S, sulphate concentration and pH) and under pipe modifications (coated vs uncoated). Bacterial cell density estimated by both cultivation-and DNA-based methods was low in the corroded sewer samples. Pyrosequencing and cloning showed that Mycobacterium and Acidithiobacillus dominated the acidophilic microbial communities. Methylacidiphilum was also dominant in samples where methane was detected. Correlation analysis indicated that Mycobacterium and Acidithiobacillus were significantly affected by pH and that Mycobacterium could better withstand highly acidic conditions compared to Acidithiobacillus. Conclusions: Communities dominated by Mycobacterium favoured conditions in the lined sewer pipes, while communities with a higher relative abundance of Acidithiobacillus favoured the unlined sewer pipes. Significance and Impact of the Study: Identifying the key micro-organisms involved in MICC and knowing how they interact with their environment are essential aspects for identifying steps towards concrete corrosion management.