Study On Geosmin Producing Microbial Communities In The RAW Water Of Huangpu River In Winter

Geosmin,a common odor rising in water supply,is widely found in surface water of China,causing great negative impact on the production and people’s living.The concentrations of geosmin in surface water are shifted along with the compositions of microbial community,as well as the transfer of seasons.Based on the shift properties of geosmin concentration in the raw water of Huangpu River,it was proposed to determinate the geosmin concentration and collect the corresponding microbial samples regularly through DNA extraction and High through-put sequencing to illustrate the odorous compounds production mechanism by comparing the samples from summer water and winter water at the microbial level.Therefore,According to the comparative analysis of microbial population structure in the raw water,Cyanobacteria might not be the mainly potential geosmin-producing microbe,for GPXI（Microcystis）and GPIIa（Synechococcus）were bloomed in Summer rather than Winter,while in winter samples the hgcI_clade（Candidatus_Nanopelagicales）and CL500₂9_marine_group take the highest abandunce which belong to Actinobacteria,not streptomycetes.It was speculated that cyanobacteria produced geosmin intracellularly in summer;while with decomposition of cyanobacteria,actinobacteria became the dominant genera in winter,which require exogeous source like vitamin,amino acid continuously due to the lack of corresponding gene sequences,therefore,the geosmin produced intracellularly was released into water.As another potential geosmin producing microbe,Actinobacteria was much higher in Winter than Summer,like Flavobacterium,whereas it can’t be classified into the genus level in this study.After the analyzing of environmental factors,both the origin linear fit and co-occurrence network analysis results show the turbidity and nutrition including NH₃-N and TP have the closest relationship with geosmin concentration,which favored the production and release of geosmin obviously.Besides,with the heatmap,Novosphigobium,Sphigomonas and Pseudomonas were found to be positively correlated with the production and biodegradation of geosmin.,verifying the growth of cyanobacteria in summer was proliferated by actinobacteria in winter,and the olfactory mechanism of the release of geomsin into the water.The qPCRresult showed that the summer abundance of the geoA gene was significantly higher than that in winter,and the relative copy number was20-60 times that of the winter water sample,which confirmed that the taste and odor problem outbroke in Huangpu River was because cyanobacteria produced geosmin in summer internally and actinobacteria released geosmin out of cells in winter.Based on the results of linear fitting and co-network analysis,this study also proposed an warning plam and in-situ reduction scheme for the control of the olfactory substances in the raw water of Huangpu River,which provided a theoretical reference for the treatment of raw water.