Exploration of the key functional strains from an azo dye degradation microbiota by DGGE and high-throughput sequencing technology. Dynamic change of a thermophilic microflora

In this study, a previously developed thermophilic microbiota that can effectively degrade azo dyes was used as the research target. To gain further insight into the key microbes of this microbiota, dilution-to-extinction approach combined with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and Illumina high-throughput sequencing technology (HTST) was firstly utilized. It was found that the decolorization efficiency and the related enzymatic activities (azoreductase, laccase, lignin peroxidase and manganese peroxidase) decreased with the increment of dilution ratios after serially diluting the microbiota, especially for high dilutions (10−9 and 10−11). Meanwhile, the decolorization situation deteriorated obviously (the original black color was still remained) in these dye solutions. The further combination analysis of PCR-DGGE and HTST results indicated the bacterial diversity was significantly reduced under high dilutions (10−9 and 10−11). It was found the strains belonging to Tepidiphilus sp. almost disappeared from the degradation solution with the dilution ratios increased over 10-7, where the diluted microbiota almost lost their decolorization ability. These results indicated the dilution ratio of 10−7 is the critical point for effective azo dyes decolorization of the microbiota, and the strains belonging to Tepidiphilus sp. were identified as the key functional microbes of this microbiota for effective azo dyes decolorization. Besides, the synergistic action of other microbes, such as Anoxybacillus sp. and Bacillus sp., were found can promote the decolorization process by secreting the azoreductase and laccase. Moreover, Caloramator sp. in the microbiota were found have ability to degrade proteins and amino acids, which might further promote the degradation process with other textile dyes degradation microbes.