Abstract
BackgroundBacterial community play a key role in environmental and ecological processes in river ecosystems. Rivers are used as receiving body for treated and untreated urban wastewaters that brings high loads of sewage and excrement bacteria. However, little is known about the bacterial community structure and functional files in the rivers around the eutrophic Chaohu Lake, the fifth largest freshwater lake in China, has been subjected to severe eutrophication and cyanobacterial blooms over the past few decades. Therefore, understanding the taxonomic and functional compositions of bacterial communities in the river will contribute to understanding aquatic microbial ecology. The main aims were to (1) examine the structure of bacterial communities and functional profiles in this system; (2) find the environmental factors of bacterial community variations.ResultsWe studied 88 sites at rivers in the Chaohu Lake basin, and determined bacterial communities using Illumina Miseq sequencing of the 16 S rRNA gene, and predicted functional profiles using PICRUSt2. A total of 3,390,497 bacterial 16 S rRNA gene sequences were obtained, representing 17 phyla, and 424 genera; The dominant phyla present in all samples were Bacteroidetes (1.4-82.50 %), followed by Proteobacteria (12.6–97.30 %), Actinobacteria (0.1–17.20 %). Flavobacterium was the most numerous genera, and accounted for 0.12–80.34 % of assigned 16 S reads, followed by Acinetobacter (0.33–49.28 %). Other dominant bacterial genera including Massilia (0.06–25.40 %), Psychrobacter (0-36.23 %), Chryseobacterium (0.01–22.86 %), Brevundimonas (0.01–12.82 %), Pseudomonas (0-59.73 %), Duganella (0.08–23.37 %), Unidentified Micrococcaceae (0-8.49 %). The functional profiles of the bacterial populations indicated an relation with many human diseases, including infectious diseases. Overall results, using the β diversity measures, coupled with heatmap and RDA showed that there were spatial variations in the bacterial community composition at river sites, and Chemical oxygen demand (CODMn) and (NH4+ )were the dominant environmental drivers affecting the bacterial community variance.ConclusionsThe high proportion of the opportunistic pathogens (Acinetobacter, Massilia, Brevundimonas) indicated that the discharge of sewage without adequate treatment into the rivers around Chaohu Lake. We propose that these bacteria could be more effective bioindicators for long-term sewage monitoring in eutrophic lakes.
Highlights
Bacterial community play a key role in environmental and ecological processes in river ecosystems
Many studies have focused on bacterial community composition (BCC) in the water body of lakes [5,6,7,8,9,10], BCC in the input rivers around lakes has not been examined in as much detail
Total nitrogen (TN) concentration ranged from 0.71 mg L− 1 at C45 to 18.80 mg L− 1 at C25, Total phosphorus (TP) concentration ranged from 0.03 mg L− 1 at C45 to 3.00 mg L− 1 at C25 and Chemical oxygen demand (CODMn) concentration ranged from 1.43 mg L− 1 at C81 to 16.71 mg L− 1 at C25
Summary
Bacterial community play a key role in environmental and ecological processes in river ecosystems. As a crucial constituent of the river ecosystem, microbes are widely distributed in water column and are diverse in terms of numbers of species They play a key role in the mineralization of organic matter, and biogeochemical processes [3, 4]. Rivers are often used as receiving body for treated and untreated urban wastewaters [12], which brings high loads of sewage and excrement bacteria [13]. These bacterial genera usually include waterborne pathogens which are a danger to human health [14,15,16]. The taxonomic and functional compositions of bacterial communities, and the influencing factors in the river around lakes have been largely ignored and the investigations are crying needed
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