Bradymonas Sediminis FA350~T Predation Effect On Microbial Community Structure And Establishment Of Genetic Operation System

As the largest habitat on earth,the ocean contains microbial resources that have an important impact on maintaining various biological and abiotic activities in the ocean.Marine bacteria are regulated by various factors,and the predation between microorganisms may be an important biological regulation factor affecting the composition of marine bacteria.Phage infection and protozoan predation are considered to be the driving force for biological regulation of the establishment of marine microbial communities.Recent studies have shown that predatory bacteria may also be one of the factors regulating the composition of marine microorganisms.It helps to better understand the evolution of marine microbial communities.This paper explores the impact of marine predatory bacteria B.sediminis FA350T on marine sediment microbial communities through microcosmic technology.The PCoA results show that the changes in the microbial community in the microcosm are mainly divided into three periods,the early stage(0-3 d),the middle stage(3-7 d)and the end stage(7-14 d)of the experiment.At the early and middle stage of the experiment,the differences in microbial community composition were not obvious.The end stages of the experiment were the period when the influence of B.sediminis FA350T on the microbial community structure appeared.Species composition analysis showed that the addition of B.sediminis FA350T caused the abundance of Flavobacteriales,Rhizobiales and other groups to decrease,while the abundance of Vibrionales,Alteromonales and other groups increased significantly.Co-occurrence network analysis results showed that B.sediminis FA350T changed the co-occurrence pattern among microorganisms.These results indicate that B.sediminis FA350T may have an important regulatory effect on the microbial community.Relying on the marine microbial strain resource platform of Shandong Province,a total of 15 strains of flavobacterium and B.sediminis FA350T were selected to evaluate the predation effect,and further explore whether the Flavobacteriales group significantly reduced during the microcosm experiment due to the predation effect of B.sediminis FA350T.Experimental results show that B.sediminis FA350T can prey on 86.7%Flavobacteriales.At the same time,this experiment evaluated the predation potential of B.sediminis FA350T to Flavobacteriales by RT-PCR absolute quantitative method.The results showed that the survival rate of prey bacteria was about 0.1%,indicating that B.sediminis FA350T had a high predation potential for Flavobacteriales.This study attempts to screen predatory-defective mutants by homologous recombination or insertion mutation to gain a deeper understanding of the predation mechanism of bradymonas.In this paper,a variety of B.sediminis FA350T antibiotic conversion concentration and voltage,resuscitation time and washing conditions,etc.were determined.Based on the current research on genes related to predatory bacteria,a number of homologous genes in the genome of B.sediminis FA350T were selected for structural prediction.Based on the research progress of genes related to predation by predatory bacteria,this study predicts the structure of multiple homologous genes of predation-related genes and constructs a mutation vector.The results show that the protein structure of B.sediminis FA350T is different from the reported protein structure.Most of the mutation vectors were constructed successfully,but no mutants with deletion of predation-related genes were screened.In this study,two mutants suspected to have reduced predation were screened by transposon insertion mutation.One of the mutants whose predation phenotype was significantly weakened H5-9 mutant gene and growth results showed that multiple genes were mutated,the mutants increased their growth ability,and their biofilm formation ability was weakened,but the transposon insertion mutation was not obtained point.This study shows that the predatory bacteria B.sediminis FA350T changed the microbial community structure of marine sediments,suggesting that predatory bacteria such as bradymonas also play an important role in the evolution of marine microbial communities.The role of predatory bacteria such as bradymonas in marine ecosystems provides the basis.This study constructed the genetic operation system of bradymonas,which will provide a technical basis for further research on the predation mechanism of bradymonas and the effect of bradymonas on the structure of marine microbial communities.