Study On Microbial Stucture Of Heavy Polluted River And Its Response To Environmental Factors

This study was conducted in the summer of 2017?17su?,winter of 2017?17wi?,spring of 2018?18sp?,and summer of 2018?18su?.A total of 7 heavy rivers in the small watershed of the Yongan River and the upper and lower reaches of the Yongan River have been identified.The environmental factors?dissolved oxygen DO,chemical oxygen demand COD,ammonia nitrogen NH₃-N,and total phosphorus TP?of rivers with 0.5 m depth were measured.Combined with high-throughput metering technology,the composition and composition of bacteria in heavily polluted rivers and The characteristics of environmental factors and bacterial aggregation composition and differences in different river sections in different periods were analyzed,and the response relationship between bacterial aggregation and environmental factors in heavily polluted rivers was explored together.According to the characteristics of the interaction between microorganisms and environmental factors,a microbial indicator with an environmental indicator function is screened,and the indicator function is preliminary explored.The findings are as follows:Analysis of river environmental factors in the study area revealed that the field investigation at 17su was in a black and odorous state with low DO content;17wi and18sp study area DO COD,NH₃-N and TP are seriously polluted at most below the detection limit.The 18su has high DO content and COD,NH₃-N.And TP content is basically below the surface level V water.The water quality has improved significantly.The overall water quality is:18su is better than 18sp and 17wi is better than 17su.Using high-throughput sequencing technology to analyze the microbial community structure in the study area,it was found that the bacterial community diversity 18su was significantly higher than the other three periods,with an overall performance of 18su>17su>17wi?18sp.In the analysis of the composition of the bacterial community,a total of 11 classes and 45 classes were obtained from each sample point.The dominant Class are Gammaproteobacteria in Proteobacteria.The composition characteristics of bacterial phylum levels and phyla levels at different periods are obvious,and the differences between samples are significant.Analysis of the genus Mycobacterium genus showed significant differences in different points.Vibrio was the dominant genus at 17su.At 17wi and 18sp,East and West Cross River bacterial The composition is quite different.Arcobacter in the East Cross River Genus is the main dominant genus,and its relative abundance is 20.11%64.00%.At 18su,the relative abundance differences among other genus were small.The distribution is relatively even,among which Cyanobium?PCC-6307 and Hydrogenophaga are relatively abundant.The characteristics of bacterial community composition in different periods were obvious,and the differences were significant.By PCA analysis,it was found that 17su,18su and17wi,18sp were significantly different,17su and 18su were significantly different,the bacterial community structure was significantly different,and the bacterial community of East and West cross river was significantly different at 17su.The community structure of 18 su was little different.Through the analysis of genus level LEfSe,the key species with significant differences in different periods were identified.The results showed that in 17su g?Geobacter?o?Saccharimonadales and g?Vibrio is the smallest taxon with significant difference,in 18su g?Cyanobium?PCC?6307?o?Chloroplast and c?Chlorofloxia is the smallest taxon with significant differences,in which g?Vibrio and G?Cyanobium?PCC?6307 is the main characteristic genus with high relative abundance.The water environment at different points in the study area is very different,and the bacterial community structure shows similar conditions.In order to investigate the response relationship between bacterial community structure and river environmental factors,Pearson correlation analysis was used to explore the response relationship from the diversity and genera levels.The results showed that the bacterial community structure in the study area was greatly affected by DO,COD,NH₃-N,and TP,and overall DO>COD>NH₃-N?TP;the relative abundance of the top 30 bacteria and 4environmental factors In the correlation analysis,30 genus were mainly divided into four bacterial groups.There are 11 genus in the first group,including Unclassified?Novosphingobium?Hydrogenophaga?Candidatus?Aquiluna?hgcI?clade?CL500-29?marine?group?f??Methylophilaceae?Unclassified?Alsobacter?Cyanobium?PCC-6307?Rhodobacter and Candidatus?Aquirestis.The environment is characterized by high DO content and low pollution factor content.There are 10 genus in the second group,including Acinetobacter?Flavobacterium?Methylotenera?Polynucleobacter?Pseudorhodobacter?GKS98?freshwater?group?C39?Malikia?Limnohabitans and Rhodoferax,its environmental characteristics are not significant.There are 8 genus in the third area,including Arcobacter?Macellibacteroides?Pseudomonas?Janthinobacterium?Trichococcus?Aeromonas?Geobacter and Tolumonas,the environmental characteristics are extremely high COD pollution.The fourth group of bacteria includes one genus Vibrio,which is characterized by high-intensity domestic sewage pollution and black and smelly water.Based on the identified key bacterial genus,significantly different bacterial genus and strong response bacterial genus,etc.,the indicators that have an indicator effect on the river environment were screened and discussed.From the two aspects of bacterial community and environmental indicator function,seven loops were selected to indicate the specific microbial environmental conditions,specific pollutants,and environmental risks of special rivers.These indicators were Ace,Shannon,CL500-29?marine?group,Cyanobium?PCC-6307.,Candidatus?Aquirestis,Arcobacter,and Vibrio,and through the literature analysis,discussed its indicating function,Ace can indicate the degree of pollution of the river,and as the degree of pollution decreases,the Ace index increases;Shannon index should not be used as an indicator;CL500 Some detections of29?marine?group and Cyanobium?PCC-6307 may indicate a light or moderate eutrophication state;a large number of Arcobacter detections indicate that the river may be polluted by domestic sewage and there is a high risk of microbial pathogenicity;a large number of detections by Vibrio It is possible to indicate to some extent that aquatic organisms such as fish,shellfish and shrimp may be infected,and that there is a risk of mass death.