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Suspended particles in water can shelter both microorganisms and contaminants. However, the emerging pollutants antibiotic resistance genes (ARGs) in free-living (FL) or particle-attached (PA) bacteria in aquatic environments are less explored. In this study, we compared the free-living and particle-attached ARGs during four seasons in the Yellow River using high-throughput quantitative PCR techniques and 16S rRNA gene sequencing. Our results demonstrated that both the free-living water and particles were dominated by tetracycline and beta-lactamase resistance genes. The PA-ARGs had a higher absolute abundance than FL-ARGs in the Yellow River, regardless of the season. Both PA-ARGs and FL-ARGs had the highest absolute abundance and diversity during winter. Mobile genetic elements (MGEs) were the dominant driver for both size-fractionated ARGs. However, the microbiome had less influence on PA-ARG profiles than the FL-ARG profiles, while the effects of the heavy metals on ARGs were negligible. The community assembly of both FL-ARG and PA-ARG can be explained by neutral processes. Several opportunistic pathogens (e.g., Escherichia coli) associated with human health exhibited a higher relative abundance in the particles than during a free-living lifestyle. Parts of these pathogens were potential ARG hosts. As such, it is important to monitor the ARGs and opportunistic pathogens from size-fractionated bacteria and develop targeted strategies to manage ARG dissemination and opportunistic pathogens to ensure public health. [Display omitted] • The PA-ARGs in the Yellow River had higher diversity and abundance than FL-ARGs. • The effects of the heavy metals on size-fractionated ARGs were negligible. • Both FL-ARG and PA-ARG community assembly can be explained by neutral processes. • Opportunistic pathogens Escherichia coli had higher abundance in particles. [ABSTRACT FROM AUTHOR]

The prevalence and transmission of antibiotic resistance genes (ARGs) and opportunistic pathogens in water environments can pose great threat to public health. However, the dissemination of ARGs and opportunistic pathogens from water environments to humans has been poorly explored. Here, we employed 16S rRNA gene sequencing and high-throughput quantitative PCR techniques to explore the seasonal distribution of ARGs and opportunistic pathogens in the Yellow River water (source water) and tap water, as well as their relationships with healthy humans at Lanzhou, China. Physiochemical analysis was applied to detect water quality parameters and heavy metal contents. The absolute abundance and diversity of ARGs in the Yellow River and tap water demonstrated distinct seasonal patterns. In winter, the Yellow river water had the highest ARG abundance and diversity, while tap water owned the lowest. Mobile genetic elements (MGEs) were the predominant driver of ARG profiles in both the Yellow river and tap water. Null model analysis showed that ARG assembly in the Yellow River was more influenced by stochastic processes than tap water and this was independent of seasons. Total organic carbon and arsenic contents exhibited positive correlations with many ARGs. Opportunistic pathogens Aeromonas and Pseudomonas may be potential hosts for ARGs. Approximately 80% of detected ARGs were shared between water samples and the human gut. These persistent ARGs could not be entirely eliminated through drinking water treatment processes. Thus, it is crucial to protect sources of tap water from anthropogenic pollution and improve water treatment technologies to reduce the dissemination of ARGs and ensure drinking-water biosafety for human health. [Display omitted] • The ARG profiles in the Yellow River and tap water had distinct seasonal patterns. • MGEs were the key driver for ARG profiles in the Yellow River and tap water. • ARGs assembly in the Yellow River had more stochastic processes. • Opportunistic pathogens Aeromonas and Pseudomonas may be potential hosts for ARGs. • Persistent ARGs cannot be entirely eliminated via drinking water treatment process. [ABSTRACT FROM AUTHOR]

As a common natural phenomenon, corpse decomposition may lead to serious environmental pollution such as nitrogen pollution. However, less is known about antibiotic resistance genes (ARGs), an emerging contaminant, during corpse degradation. Here, ARGs and microbiome in three soil types (black, red and yellow soil) have been investigated between experimental and control groups based on next-generation sequencing and high-throughput quantitative PCR techniques. We found that the absolute abundance of total ARGs and mobile genetic elements (MGEs) in the experimental groups were respectively enriched 536.96 and 240.60 times in different soil types, and the number of ARGs in experimental groups was 7–25 more than that in control groups. For experimental groups, the distribution of ARGs was distinct in different soil types, but sulfonamide resistance genes were always enriched. Corpse decomposition was a primary determinant for ARGs profiles. Microbiome, NH 4 + concentrates and pH also significantly affected ARGs profiles. Nevertheless, soil types had few effects on ARGs. For soil microbiome, some genera were elevated in experimental groups such as the Ignatzschineria and Myroides. The alpha diversity is decreased in experimental groups and microbial community structures are different between treatments. Additionally, the Escherichia and Neisseria were potential pathogens elevated in experimental groups. Network analysis indicated that most of ARGs like sulfonamide and multidrug resistance genes presented strong positively correlations with NH 4 + concentrates and pH, and some genera like Ignatzschineria and Dysgonomonas were positively correlated with several ARGs such as aminoglycoside and sulfonamide resistance genes. Our study reveals a law of ARGs' enrichment markedly during corpse decomposing in different soil types, and these ARGs contaminant maintaining in environment may pose a potential threat to environmental safety and human health. [Display omitted] • Corpse decomposition changes soil environment. • Corpse decomposition causes the accumulation of ARGs in all soil types. • Soil types have few impact on ARGs. • Treatment, microbiome, NH 4 + concentrates and pH are primary determinants. • ARGs are correlated with integrons, NH 4 +, pH and microbes during corpse decay. [ABSTRACT FROM AUTHOR]

Animal carcass decay produces many poisonous metabolites and chemical pollutants, which pose potential ecological risks to the aquatic environment and human health. However, the effects of animal cadaver decomposition on high-risk antibiotic resistance genes (ARGs) and potential pathogens in different water types are still unknown. In this study, fifteen freshwater economic fish (Carassius auratus) corpses were put into three types of water (i.e., pond water, tap water, and domestic sewage) for a 100-day decomposition. Next generation sequencing and HT-qPCR were used to illustrate how corpse decomposition affected microbial communities and ARG profiles. Our results revealed that fish corpse degradation caused similar resistomes and microbiome in different water types. MLSB (Macrolide-Lincosamide-Streptogramin B), β-lactamase, sulfonamide, tetracycline resistance genes and transposase genes in the experimental groups were increased. Among them, tetracycline resistance genes were enriched by 224 to 136,218-fold during the process of corpse degradation. Furthermore, high-risk ARGs (ermB , floR and dfrA1), which resist to MLSB, multidrug and sulfonamide respectively, were significantly enriched in the cadaver groups and had co-occurrence patterns with opportunistic pathogens, such as Bacteroidetes , which was more than 37 times in carcass groups than that in control groups. The study is able to draw a general conclusion that cadaver decomposition of freshwater economic fish deteriorates the aquatic environment by affecting high-risk ARGs and pathogenic microorganisms regardless of water types, which poses potential threats to human health. Therefore, timely management and treatment of animal carcasses is of great significance to the protection of water environment. [Display omitted] • Fish corpse degradation caused similar resistomes and microbiome in different water types. • Fish cadaver decomposition led to enrichment of opportunistic pathogens and high-risk ARGs. • Corpse decay, microbiomes, MGEs and environment factors primarily affect ARG profiles. • Timely management and treatment of animal carcasses is of great significance to the protection of water environment. [ABSTRACT FROM AUTHOR]