Effect of lowering temperature on the function and interactions of microbial communities in micro pressure swirl reactor under low-carbon source conditions

To investigate the changes in the function and interactions of the microbial communities in a micro-pressure swirl reactor (MPSR) with low-carbon source sewage and low temperature (15, 12, and 10 degrees C), highthroughput sequencing was used to examine the reactions of microbial structures, functional profiles, and metabolic pathways to three temperatures. The results revealed that temperature altered the microbial community structure of the system, the dominant phylum in 15 degrees C was Patescibacteria, accounting for 48.09 %, and the dominant phylum in 12 degrees C was Bacteroidetes, accounting for 85.82 %. The dominant phylum in 10 degrees C was composed of Bacteroidetes, Proteobacteria, Chloroflexi, and Actinobacteria together, accounting for 38.58 %, 25.13 %, 14.40 %, and 10.56 %, respectively. The dominant genera in the system changed from a single genus: Saccharimonadales (48 %) in 15 degrees C and Niabella (73 %) in 12 degrees C, to multiple genera: Niabella, Kouleothrix, and Saccharimonadales (26 %, 11 % and 9 % respectively) in 10 degrees C. 46.34 %, 91.22 %, and 99.41 % of the main functional microorganisms were found at 15, 12 and 10 degrees C respectively demonstrating that MPSR was able to screen bacteria adapted to low temperature and low carbon source conditions. According to the analysis of metabolic pathways, higher expression of functional genes connected to the dissimilatory and assimilatory nitrate reduction, denitrification, and glutamate metabolism were observed. MPSR improved the treatment efficiency by eliminating bacteria that were unable to remove organic matters, which made MPSR remove organic pollutants more effectively under low temperatures and low carbon source conditions.