Screening And Identification Of Oligotrophic Heterotrophic Nitrifying Bacteria And Its Ammonia Removal Characteristics

In recent years,the discharge of ammonia nitrogen wastewater has gradually increased with complex composition and a rising trend of concentration.The increase of nitrogen emissions leads to a decrease of dissolved oxygen in water,and thus resulting in the gradual deterioration and eutrophication of water.However,the traditional physical and chemical methods for ammonia removal can no longer meet the current needs due to high economic costs and possible secondary pollution.Therefore,biological denitrification technology has attracted much attention.What’s more,oligotrophic bacteria can achieve the removal of ammonia nitrogen under less nutrition,which is of great significance to the treatment of environmental pollution.In this experiment,a strain able of oligotrophic heterotrophic nitrification was screened out from ammonia nitrogen micro-polluted water samples.The carbon source needed for its normal growth was about 1/100 of that of ordinary bacteria.The colony of this strain was white,smooth,neat edge and round with a diameter of about 1 mm.ESEM scanning images showed that the strain was short rod-shaped with a length of about 0.5～1.0 μm.Through the identification of the 16 S r RNA gene sequence of this bacterium,it was found that it belongs to the genus Pseudomonas,named Pseudomonas sp.N31942.By measuring the growth curve of Pseudomonas sp.N31942,it can be seen that the strain entered the logarithmic growth phase at 2h and reached the stable growth phase at12 h.The ammonia nitrogen removal rate has reached more than 80% within 10 h.During the whole growth process,the final removal rate of ammonia nitrogen reached 85%,and the strain exhibited the ability of aerobic denitrification.Single factor experiment showed that the optimal inoculum amount for ammonia removal was 1%,the optimal temperature was30℃,the pH was 7.0,and the optimal C/N was 10.Through response surface optimization and further model calculation,when the temperature was 29℃,the initial pH was 7.13,and the C/N was 10,this strain reached the highest ammonia nitrogen removal rate(86.97%).The whole genome of the strain was sequenced and the sequencing information was analyzed by bioinformatics methods.The results showed that the total length of the strain’s genome was 5.36 Mb,and the GC content was 63.54%.The predicted number of coding genes was 4790,and the average length was 993 bp.In addition,CRISPR predicted that seven regions contained in the chromosome genome of the strain were found.Different databases were used to analyze the gene function of the strain,and the protein sequence,gene function,classification information and carbohydrate enzyme content of the strain were further explored.Also,the localization analysis of the protein subcellular of this strain was carried out,and the number of signal peptides was predicted to be 527,the number of transmembrane proteins was 1136,and the number of secreted proteins was 527.