Bacteria and antibiotic resistance genes during carcass decomposition

Carcass decomposition in water may cause serious environmental pollution, which will pose a great threat to water quality and public health. However, water microbial community succession and antibiotic resistance genes (ARGs) during carcass decomposition process are less explored. Using high-throughput sequencing and high-throughput quantitative PCR techniques, the temporal succession of bacterial communities and ARGs profiles in experimental groups (fish carcasses) and control groups (no fish carcasses) containing two different types of water (the Yellow River water and tap water) from 3th to 19th day were studied. Our results showed that three parameters (pH, TOC and ORP) had linear correlations with decomposition time. Comamonas, Bacteroides and Pseudomonas significantly increased during carcass decomposition process. Alpha diversity (phylogenetic diversity and observed species (OTUs) indexes) of experimental groups was significantly lower than that in control groups. Time and treatment significantly influenced the bacterial community structures, and community dissimilarities between groups decreased over time, indicating that microbial community convergence. NH3-N, time and treatment were most important factors in determining bacteria community structures. The relative abundance of seven detected ARGs (cmlA1-01, floR, sul1, sul2, tetG-01, tetM-01 and tetQ) in the experimental groups were higher than those in the control groups. The ARGs concentrations in the experimental groups were even enriched 19-fold (minimum) to 148-fold (maximum) compared to tetQ of the Yellow River water in the control groups on 3th day. Redundancy analysis (RDA) indicated that two bacterial phyla (Firmicutes and Bacteroidetes) and environmental factors (NH3-N, ORP, CON, TDS and salinity) were significantly correlated with all detected ARGs. This study emphasizes that long-term input of nutrients causing by carcass decomposition in water firstly shifted the microbial community composition especially potential pathogens and then effected the ARGs profiles via microbial communities and environmental factors, thereby uncovering the harmful effects of related water pollution for human health.