Exploration of the key functional strains from an azo dye degradation microbial community by DGGE and high-throughput sequencing technology.

This study investigated a previously developed thermophilic microbial community with the ability to effectively degrade azo dyes. To identify the key microbes of this microbial community, a dilution-to-extinction approach was combined with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and Illumina high-throughput sequencing technology (HTST). Strains belonging to Tepidiphilus sp. almost disappeared from the degradation solution at dilution ratios above 10-7; furthermore, at this ratio, the diluted microbial community almost lost their decolorization ability, indicating this ratio as the critical point for effective azo dye decolorization. Strains belonging to Tepidiphilus sp. were indicated as possible key functional microbes of this microbial community for effective azo dye decolorization. Moreover, the synergistic action of other microbes, such as Anoxybacillus sp., Clostridium sp., and Bacillus sp., was suggested to further promote the decolorization process by secreting azoreductase and laccase. Caloramator spp. were found have the ability to degrade proteins and amino acids, which might promote the degradation process with further degradation microbes. The loss of these bacteria might diminish the synergistic relationships among different strains, which further results in the failure of efficient azo dye decolorization and degradation by this microbial community.