National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.
Guangdong Provincial Center for Disease Control and Prevention, Guangdong, China.
Sci Total Environ. 2023 Sep 1;889:164265. doi: 10.1016/j.scitotenv.2023.164265. Epub 2023 May 19.
Estuarine ecosystems undergo pronounced and intricate changes due to the mixing of freshwater and saltwater. Additionally, urbanization and population growth in estuarine regions result in shifts in the planktonic bacterial community and the accumulation of antibiotic resistance genes (ARGs). The dynamic changes in bacterial communities, environmental factors, and carriage of ARGs from freshwater to seawater, as well as the complex interrelationships among these factors, have yet to be fully elucidated. Here, we conducted a comprehensive study based on metagenomic sequencing and full-length 16S rRNA sequencing, covering the entire Pearl River Estuary (PRE) in Guangdong, China. The abundance and distribution of the bacterial community, ARGs, mobile genetic elements (MGEs), and bacterial virulence factors (VFs) were analyzed on a site-by-site basis through sampling along the salinity gradient in PRE, from upstream to downstream. The structure of the planktonic bacterial community undergoes continuous changes in response to variations in estuarine salinity, with the phyla Proteobacteria and Cyanobacteria being dominant bacterial throughout the entire region. The diversity and abundance of ARGs and MGEs gradually decreased with the direction of water flow. A large number of ARGs were carried by potentially pathogenic bacteria, especially in Alpha-proteobacteria and Beta-proteobacteria. Multi-drug resistance genes have the highest abundance and subtypes in PRE. In addition, ARGs are more linked to some MGEs than to specific bacterial taxa and disseminate mainly by HGT and not by vertical transfer in the bacterial communities. Various environmental factors, such as salinity and nutrient concentrations, have a significantly impact on the community structure and distribution of bacteria. In conclusion, our results represent a valuable resource for further investigating the intricate interplay between environmental factors and anthropogenic disturbances on bacterial community dynamics. Moreover, they contribute to a better understanding of the relative impact of these factors on the dissemination of ARGs.
由于淡水和海水的混合，河口生态系统会发生显著而复杂的变化。此外，河口地区的城市化和人口增长导致浮游细菌群落的转移和抗生素耐药基因（ARGs）的积累。从淡水到海水的细菌群落、环境因素和 ARG 的携带、以及这些因素之间的复杂相互关系的动态变化尚未完全阐明。在这里，我们基于宏基因组测序和全长 16S rRNA 测序，对中国广东的整个珠江河口（PRE）进行了全面的研究。通过在 PRE 沿盐度梯度进行采样，从上游到下游，对细菌群落、ARGs、移动遗传元件（MGEs）和细菌毒力因子（VF）的丰度和分布进行了站点分析。浮游细菌群落的结构会随着河口盐度的变化而不断变化，整个区域的优势细菌门为变形菌门和蓝细菌门。ARGs 和 MGEs 的多样性和丰度随着水流方向逐渐降低。大量的 ARGs 由潜在的致病细菌携带，尤其是在α-变形菌门和β-变形菌门中。多药耐药基因在 PRE 中的丰度和亚型最高。此外，ARGs 与某些 MGEs 的关联比与特定细菌类群的关联更密切，并且主要通过 HGT 而不是垂直转移在细菌群落中传播。各种环境因素，如盐度和营养浓度，对细菌群落结构和分布有显著影响。总之，我们的结果为进一步研究环境因素和人为干扰对细菌群落动态的复杂相互作用提供了有价值的资源。此外，它们有助于更好地了解这些因素对 ARG 传播的相对影响。
