Isolation and characterization of microorganisms involved in the biodeterioration of concrete in sewers

The majority of studies concerning the microbiology of microbially induced concrete deterioration have indicated that the autotrophic sulfur oxidizing organism Thiobacillus thiooxidans and other Thiobacilli are the causative organisms. In this study, nine heterotrophic bacteria, two autotrophic bacteria and four fungi were isolated from corroding concrete sewage collection pipes in Houston, TX, USA. The microbial populations of samples of corroding concrete from the sewage collection system in Melbourne, Australia were also examined. The isolates were characterized by their colonial morphologies, substrate utilization and 16S rRNA sequences. Analysis of 16S rRNA sequences indicated the presence of Bacillus, Ochrobactrum anthropi, Microbacterium and T. thiooxidans in the samples. Results of substrate utilization tests demonstrated that all the fungi and six of the heterotrophic bacteria, although found in most of the sampled sites, did not use thiosulfate or elemental sulfur as sole energy source once isolated as pure cultures. Some were found to use thiosulfate as co-cultures with other organisms that were lost when co-cultures were separated. The findings verified the complexity of the microbiological population and the succession theory involved in the corrosion process.