Microbial community and antibiotic resistance genes of biofilm on pipes and their interactions in domestic hot water system.

This study aimed to explore the dynamics of microbial communities and antibiotic resistance genes (ARGs) during biofilm formation on polypropylene random (PPR), polyvinyl chloride and stainless steel pipes in domestic hot water system (DHWS), as well as their interactions. Full-scale classification was used to divide abundant and rare genera with 0.1% and 1% as the thresholds. The biofilm community structure presented a temporal pattern, which was mainly determined by conditionally rare or abundant taxa (CRAT) and conditionally rare taxa (CRT). The dynamics of microbial community during biofilm formation were observed, and the effect of pipe material on conditionally abundant taxa (CAT) and CRAT was greater than CRT and rare taxa (RT). CRAT showed the most complex internal associations and were identified as the core taxa. Notably, CRT and RT with low relative abundance, also played an important role in the network. For potential pathogens, 17 genera were identified in this study, and their total relative abundance was the highest (3.6-28.9%) in PPR samples. Enterococcus of CRAT was the dominant potential pathogen in young biofilms. There were 36 more co-exclusion patterns (140) observed between potential pathogens and nonpathogenic bacteria than co-occurrence (104). A total of 38 ARGs were predicted, and 109 negative and 165 positive correlations were detected between them. Some potential pathogens (Escherichia/Shigella and Burkholderia) and nonpathogenic bacteria (Meiothermus and Sphingopyxis) were identified as the possible hosts of ARGs. This study is helpful for a comprehensive understanding of the biofilm microbial community and ARGs, and provides a reference for the management and biosafety guarantee of newly-built DHWS.