Bacterial Diversity And Bioactivity Assessment In Fangchenggang Coastal Shoal Of Beibu Gulf

Beibu Gulf,a semi-closed bay surrounded by land on three sides,is located in tropical and subtropical regions,it is a traditional fishing ground and a center of rich biodiversity,which also contains rich bacterial resources.In this study,the bacterial diversity and its relationship with environmental factors were analyzed in the sediment samples from five sample areas(mangrove reserve sediment,mangrove rhizosphere sediment,shrimp and crab pond sediment,Pearl culture sediment,paper mill polluted sea sediment)in Fangchenggang coastal shoal of Beibu Gulf by using the techniques of cultivation-independent and cultivation-dependent.The abundance and difference of functional genes and resistance genes among the five samples were analyzed by metagenomic sequencing.Functional genes and antimicrobial activity of the isolated and purified strains were screened so as to excavate the potential strains with biological activity.Firstly,high-throughput sequencing analysis of bacterial 16 S r RNA gene was used,combined with differences in environmental factors,so as to understand the bacterial diversity,abundance and correlation with environmental factors in the five sample regions.After species annotation,abundant bacterial resources were detected in the samples,which belonged to more than 50 phyla,more than 70 classes,more than 100 orders,more than 300 families and more than 1000 genera.At the phylum level,the proportion of Proteobacteria was much higher than that of other species,belonging to the dominant species,and was greatly affected by the contents of organic matter,potassium and salt.Secondly,the abundance and differences of functional genes and resistance genes in the five samples were studied by metagenomic sequencing.The results of functional gene annotation showed that a large number of genes were annotated to the related functions of KEGG,egg NOG and CAZy functional databases,and in KEGG,the abundance of genes annotated to metabolism was the highest;Among egg NOG,the abundance of genes annotated to energy production and conversion was the highest;In CAZy,the gene abundance of GHs and GTs was annotated to be the highest.The results of resistance gene annotation showed that a large number of genes were annotated into the resistance gene ARO,and the highest abundance of ARO gene was ade F.Thirdly,by using the pure culture technology,different separation media were selected to separate bacteria from the sediment samples from 5 sample areas,and 338 strains of bacteria were finally isolated,belonging to 3 phyla,4 classes,16 orders,24 families and 39 genera.Among them,there were 9 potential new taxa,accounting for 2.7%.Finally,functional genes were screened for 338 strains isolated from pure culture,and123 strains containing functional genes were screened,the proportion of Malacidin,Lugdunin,Teixobactin,Leinamycin,Glutarimide,Salinomycin and Diterpenes were 2.1%,0.6%,2.1%,26.3%,7.1%,8.9% and 9.2%,respectively.The antimicrobial activity of 141 strains after elimination was screened,and 28 strains showed antimicrobial activity,The proportion of strains against Staphylococcus aureus,Bacillus subtilis,Mycobacterium tuberculosis,Escherichia coli,Candida albicans and Aspergillus niger were 9.2%,5.7%,14.2%,4.3%,7.8% and 5.0%,respectively.In conclusion,there are abundant bacterial resources,a large number of functional genes and resistance genes in the coastal shoal samples of Fangchenggang,Beibu Gulf,which can provide a rich bacterial and gene bank for the development of natural products in the Beibu Gulf,and its development potential is huge,and it is worthy of further study.