RESUMEN
The occurrence of antibiotic resistance genes (ARGs) and their associated environmental factors in estuaries are poorly understood. In this study, we comprehensively analyzed ARGs in both water and sediments from inlet to outlet of the Yangtze Estuary, China. The relative abundances of ARGs were higher in the turbidity maximum zone (TMZ) than other sites, implying that suspended particulate matter (SPM) was the major reservoir for ARGs in water. ARGs showed an increasing trend from inlet to outlet in sediments. Positively correlation between intI1 and sul1 in both water and sediments indicated that sul1 may be regulated by intI1. Correlation analysis and redundancy analysis showed that the spatial variations of estuarine ARGs were positively correlated with sample properties (e.g., temperature, SPM, pH) and chemical pollutants (e.g., heavy metals and antibiotic residues), among which chemical pollutants were the major drivers for the ARG distribution in both water and sediments.
Asunto(s)
Estuarios , Contaminantes Químicos del Agua/análisis , Antibacterianos/análisis , Bahías , China , Farmacorresistencia Microbiana , Monitoreo del Ambiente , Genes Bacterianos , Sedimentos GeológicosRESUMEN
Many studies have examined the acute toxicity of nanoparticles (NPs) towards model bacteria. In this study, we report the time-dependent effects of ZnO NPs on native, selected Zn-resistant and dominant bacteria in estuarine waters. An initial inhibition of bacterial growth followed by a recovery at 24â¯h was observed, and this rebound phenomenon was particularly notable when the raw water samples were treated with relatively high ZnO NP concentrations (1 and 10â¯mg/L).By comparing the groups treated with Zn2+, Zn2+ was shown to largely explain the acute cytotoxic effect of ZnO NPs on bacteria in raw waters. Furthermore, similar to the native bacteria, especially the dominant bacteria, the viability of Escherichia coli (E. coli) decreased with the increasing treatments time and the concentrations of ZnO NPs in water with different salinities. Moreover, the expression of Zn-resistance genes including zntA and zntR in E. coli suggested that the Zn-resistance system in E. coli can be activated to defend against the stress of Zn2+ released from ZnO NPs, and salinity may promote this process in estuarine aquatic systems. Thus, the effect of ZnO NPs on bacteria in estuarine water bodies is likely determined by the synergistic effect of environmental salinity and dissolved Zn ions. As such, our findings are of high relevance and importance for understanding the ecological disturbances caused by anthropogenic NPs in estuarine environments.
Asunto(s)
Bacterias/efectos de los fármacos , Nanopartículas del Metal/toxicidad , Contaminantes Químicos del Agua/toxicidad , Óxido de Zinc/toxicidad , Estuarios , SalinidadRESUMEN
In the contaminated coastal sediments, variations of microbial community can reflect the impact of anthropogenic activities. The identification, evaluation and monitoring of the potential bio-indicator species and biomarker communities are vital for the ecological studies in sedimentary environments. Based on the high-throughput sequencing, the microbial communities were characterized in the sediments along the Yangtze Estuary and its coastal area. The results showed that the structure and composition of microbial communities varied greatly among different sampling sites at the phyla level, especially for Euryarchaeota. Metabolic pathway and quantitative PCR analyses suggested that the methane metabolism-related microbes were mainly included in the phylum of Euryarchaeota. Elevated abundances of methane metabolism-related microbes were found at Shidongkou (SDK) and Wusongkou (WSK), where microbes were seriously impacted by the wastewater treatment plant (WWTP) effluent and urban runoff. By comparing with the Euryarchaeota in WWTP sludge, the relatively high abundance of Euryarchaeota in sediment at SDK may be mainly related to the massive growth of indigenous species, promoted by anthropogenic nutrients. Moreover, redundancy discriminant analysis and correlation analysis revealed that methanogens and methanotrophs mainly respond to the nutrients and metals, such as total organic carbon, total phosphorus, total nitrogen, SO42-, NO2-, NH4+, Cr, and Zn, which were often related to human activities. Network analyses showed that the species related to the metabolism of methane may play a vital role in the interassociation among different microbial communities. Therefore, methanogens, methanotrophs and their community compositions could be considered as potential bio-indicator species and biomarker communities, indicating anthropogenic activities in the sediments along the Yangtze Estuary and its coastal area.
Asunto(s)
Archaea/aislamiento & purificación , Bacterias/aislamiento & purificación , Estuarios , Sedimentos Geológicos/microbiología , Microbiota , Biomarcadores/análisis , China , Ambiente , ARN de Archaea/análisis , ARN Bacteriano/análisis , ARN Ribosómico 16S/análisisRESUMEN
Antibiotics resistance genes (ARGs) are considered as an emerging pollutant among various environments. As a sink of ARGs, a comprehensive study on the spatial and temporal distribution of ARGs in the estuarine sediments is needed. In the present study, six ARGs were determined in sediments taken along the Yangtze Estuary temporally and spatially. The sulfonamides, tetracyclines and fluoroquinolones resistance genes including sul1, sul2, tetA, tetW, aac(6')-Ib, and qnrS, were ubiquitous, and the average abundances of most ARGs showed significant seasonal differences, with relative low abundances in winter and high abundances in summer. Moreover, the relative high abundances of ARGs were found at Shidongkou (SDK) and Wusongkou (WSK), which indicated that the effluents from the wastewater treatment plant upstream and inland river discharge could influence the abundance of ARGs in sediments. The positive correlation between intI1 and sul1 implied intI1 may be related to the occurrence and propagation of sulfonamides resistance genes. Correlation analysis and redundancy discriminant analysis showed that antibiotic concentrations had no significant correlation to their corresponding ARGs, while the total extractable metal, especially the bioavailable metals, as well as other environmental factors including temperature, clay, total organic carbon and total nitrogen, could regulate the occurrence and distribution of ARGs temporally and spatially. Our findings suggested the comprehensive effects of multiple pressures on the distribution of ARGs in the sediments, providing new insight into the distribution and dissemination of ARGs in estuarine sediments, spatially and temporally.
Asunto(s)
Farmacorresistencia Microbiana/genética , Monitoreo del Ambiente , Estuarios , Genes Bacterianos , Sedimentos Geológicos/química , Contaminación del Agua/estadística & datos numéricos , China , Ríos , Estaciones del Año , Sulfonamidas/análisis , Tetraciclinas/análisis , Eliminación de Residuos Líquidos , Aguas Residuales/análisis , Aguas Residuales/química , Aguas Residuales/estadística & datos numéricos , Contaminación del Agua/análisisRESUMEN
Ubiquitous in the aquatic environment, sulphate-reducing bacteria (SRB) are considered one of the dominant microorganisms involved in the degradation of sulphate. This study focused on the spatial and temporal distributions of SRB in the Scirpus triquter rhizosphere sediments with a comparison to non-rhizosphere sediments and evaluated the implication of SRB to the bioavailability of metals in the Yangtze Estuary. The results showed that taking dsrB as the target gene, SRB abundances in rhizosphere sediments were significantly higher than those in non-rhizosphere sediments (P<0.01). SRB abundances were relatively higher in April and January than other seasons. Moreover, redundancy discriminate analysis (RDA) results indicated that sulphate, pH and TOC were the major environmental factors affecting the SRB abundance in rhizosphere sediments. The concentrations of most metals were significantly related to SRB abundance, and sulphide concentrations showed a significantly positive correlation to metal concentrations, indicating metal sulphide/metal associated sulphide could be regulated by SRB. Furthermore, electron microscope analysis found that nano-sized metal sulphide particles were ubiquitous in rhizosphere sediments and could be further taken up by plants. This study provides new insights into the immobilization and removal of heavy metals and the ecological value of the sulphate-reducing bacteria in the Yangtze Estuary.
Asunto(s)
Estuarios , Sedimentos Geológicos/química , Metales Pesados/análisis , Microbiología del Agua , Contaminantes Químicos del Agua/análisis , Biodegradación Ambiental , China , Sedimentos Geológicos/microbiología , Metales Pesados/metabolismo , Sulfatos , Contaminantes Químicos del Agua/metabolismoRESUMEN
This study was designed to investigate the characteristics of bacterial communities in intertidal sediments along the Yangtze Estuary and their responses to environmental factors. The results showed that bacterial abundance was significantly correlated with salinity, SO42- and total organic carbon, while bacterial diversity was significantly correlated with SO42- and total nitrogen. At different taxonomic levels, both the dominant taxa and their abundances varied among the eight samples, with Proteobacteria being the most dominant phylum in general. Cluster analysis revealed that the bacterial community structure was influenced by river runoff and sewerage discharge. Moreover, SO42-, salinity and total phosphorus were the vital environmental factors that influenced the bacterial community structure. Quantitative PCR and sequencing of sulphate-reducing bacteria indicated that the sulphate reduction process occurs frequently in intertidal sediments. These findings are important to understand the microbial ecology and biogeochemical cycles in estuarine environments.
Asunto(s)
Ecosistema , Estuarios , Sedimentos Geológicos/microbiología , Consorcios Microbianos , Bacterias/clasificación , China , Nitrógeno , Ríos/microbiología , SalinidadRESUMEN
Biofilms are ubiquitous throughout aquatic environments and they are thought to promote the acquisition and dissemination of antibiotic resistant genes (ARGs). This study focused on the occurrence and distribution of five types of ARG in naturally-occurring biofilms, in comparison to associated sediment and water samples, from the Yangtze Estuary, which borders the meta-city of Shanghai, China. The detection frequency and abundances of most ARGs showed the following order: biofilm > sediment > water, which can be attributed to a high level of antibiotics and metals that can accelerate the generation and propagation of ARGs in biofilms. Most of ARG abundances were contributed by extracellular DNA (eDNA) in biofilm and sediment samples. ARGs (sul1, sul2, tetA and tetW) in eDNA were significantly correlated with TOC in both biofilm and sediment samples. Furthermore, both intracellular DNA-associated ARGs per gram of microbial biomass carbon (MBC) and eDNA-associated ARGs per gram of non-MBC and were higher in biofilms than sediments, and the partitioning coefficients of ARGs in eDNA between biofilm and water were higher than those between sediment and water. Our results provide new insight for evaluating the occurrence and abundance of ARGs in aquatic environments, confirming that biofilms are a significant sink for ARGs in the estuarine environment.
Asunto(s)
Biopelículas , Farmacorresistencia Microbiana/genética , Estuarios , Genes Bacterianos , Contaminantes Químicos del Agua/análisis , Antibacterianos/análisis , China , Agua Dulce/análisis , Sedimentos Geológicos/análisisRESUMEN
In this study, the 16S rRNA-based Illumina MiSeq sequencing was used to investigate the bacterial community structure and composition of intertidal biofilm taken along the Yangtze Estuary. The results showed that 680,721 valid sequences of seven samples were assigned to 147,239 operational taxonomic units, which belonged to 49 phyla, 246 family and 314 genera. Compared to other studies on water and sediments in the study area, biofilms showed highest index of bacterial diversity and abundances. At different taxonomic levels, both dominant taxa and their abundances varied among the seven samples, with Proteobacteria as the dominant phylum in general. Principal component analysis and cluster analysis revealed that bacterial communities at WSK differed from those at other sampling sites. Salinity, dissolved oxygen, pH and nutrients were the vital environmental factors to influence the bacterial community structure of biofilms. These results may provide a new insight into the microbial ecology in estuarine environments.