Ecological Distribution Characteristics Of Aerobic Anoxygenic Phototrophic Bacteria In Wulixia Reservoir

Microscopic plankton are widely distributed and have high abundance in the water,and they occupy a very important position in the ecosystem.Moreover,Microscopic plankton play a vital role in the process of energy transfer,transformation and material cycle in the ecosystem.AAPB is a special and important photosynthetic heterotrophic microorganism in nature and have a potentially important role in the process of biogeochemical cycle.This study mainly applied molecular biology methods,such as TA cloning technology and high-throughput sequencing to explore the diversity,community distribution and influencing factors of AAPB in wulixia reservoir.We collected samples in the depth of 0m,5m and 10m in the Wulixia reservoir four times from July of 2016 to December of 2016,at the same time tested water quality parameters,such as water temperature and salinity.Water samples were filtered before collected,and then extracted the total genomic DNA of the plankton,that amplified by coded light reaction center of specific primer,and sequenced by high-throughput sequencing techniques,finally according to the functional characteristics of AAPB to analyse the diversity and community structure of AAPB.Through the analysis of water ions,we found that hydrochemical type of Wulixia reservoir was HCO₃-Ca-Mg type,that is controlled by the weathering of carbonate rocks and had a significant effect in water-rock interactions.The spatial distribution characteristics of water temperature showed a decrease trend from the surface water to the depth 10m in the summer,however,there was no obvious trends in the winter.The rate of carbon sequestration were tested by ¹⁴C in the Wulixia reservoir,and combined primary productivity and greenhouse gas emissions rate,we found that the Wulixia reservoir was atmospheric CO₂ sinks in the summer,and greenhouse gas emissions rate range from-30.14 mg·m^-2·h^-11 to-3.47 mg·m^-2·h^-1,autumn and winter were the source of atmospheric CO₂,and greenhouse gas emissions rate range from 15.57mg·m^-2·h^-11 to115.06 mg·m^-2·h^-1.The primary productivity of micro photosynthetic organisms was negatively correlated with the rate of CO₂ emissions,and had a positive correlation with the rate of CH₄ emissions,showed that the fluxes of CO₂ and CH₄ had a direct relationship with primary productivity.Quantitatively analysis of 16S rRNA gene and PufM gene by real-time fluorescence quantitative method of Realtime PCR,we found that the change trend of bacterial abundance and AAPB abundance were consistent in vertical direction,the dynamic change as fllowed:5m>0m>10m.The abundance of bacteria was significantly negatively correlated with AAPB abundance,DO,HCO₃^-and conductivity,and had a significantly positive correlation with water temperature and TOC,Influence factor of the variation in the abundance of AAPB was not consistent with the bacteria,that reflected the different seasonal patterns and environmental effects between functional bacteria AAPB and other plankton.We analyzed the source of organic carbon in the Wulixia reservoir by combining the rate C/N and?¹³C,?¹³C vary from-35.44‰to-23.54‰with an average-29.65‰,the rate of C/N vary between 2.24 and 26.46 with an average 6.10,the results showed that the source of organic matter in the Wulixia reservoir presented a strong endogenous source,that mainly controlled by plankton.According to the diversity analysis of an Alpha by statistically removed the high quality sequences of chimeras,and combined Shannon index and Simpson index,the results showed that the highest of microbial diversity appeared in WLX05 point of the third sampling,its Shannon index reached 6.42,the lowest point appeared in WLX08point of the third sampling,the Shannon index was 4.09,it was more smaller compared with the second sampling,the WLX08 point was located in the reservoir riparian zone,through the analysis of PCoA showed that the water level fluctuation of the reservoir fluctuating zone had little effect on the bacterial diversity of the fluctuating zone.Classification of dominant bacteria at the phylum level,the bacteria can be divided into Actinobacteria,Proteobacteria,Verrucomicrobia,Bacteroidetes,Cyanobacteria,Chloroflexi,Planctomycetes,Chlorobi,Firmicutes,Gemmatimonadetes,Deinococcus-Thermus,Acidobacteria,Nitrospirae,Chlamydiae and unclassified bacteria in the Wulixia reservoir.The proportion of Actinobacteria and Proteobacteria in total bacteria vary from 62.6%to 90.2%.Through the analysis of Beta diversity,we found that the differences in the community structure of each sample as follows:HgcI clade genus and cl500-29 genus of actinobacteria phylum,FukuN18 freshwater group genus of Verrucomicrobia phylum,and OM43 clade genus of Proteobacteria phylum,their abundance are very high in samples.In the microbiological family,we found that the genus of OM43 clade,Sphingomonas,Methylobacterium,Cupriavidus,Novosphingobium,Polynucleobacter,Rhodovulum,Rhodobacter,Brevundimonas,and Methyloversatilis belonged to the AAPB.Through the analysis of RNA,we found that AAPB was suitable for growth in aquatic environment of karst areas,and temperature was the main factors that directly affected the composition of AAPB community,it indicated that AAPB play a special role in the production of organic carbon in the karst surface water system,moreover the source of organic carbon in wulixia reservoir was not only from photosynthetic plants,but also photosynthetic bacteria played an important role.