Infection/Anti-infective Gene Changes Of Pseudomonas Fluorescens W-6 And Its Phage VW-6S In Coecolution

The complex interactions between phage and host play an important role in the formation of environmental microbial community structures.The co-evolution process between bacteria and phage that repeatedly produces resistance and infectivity is called antagonistic co-evolution.Bacterial-phage antagonism co-evolution plays an important role in population dynamics,evolutionary diversity,and genetic recombination.The first step of phage-infected host is adsorption.In the process of co-evolution,the host's inhibition of phage adsorption and phage-to-host adsorption capacity lead to the co-evolutionary diversity of phage adsorption sites and bacterial adsorption receptors.In this study,Pseudomonas fluorescens W-6 and its long-tailed phage VW6 S isolated from the Napahai Plateau wetland water sample were used as materials to carry out host genome-wide analysis,co-evolution,host anti-infective genes,phage infection gene changes,Host adsorption receptors and phage adsorption sites were studied.W-6 genome length is 6,109,123 bp,G+C content is 59.79%;a total of 5,474 genes are encoded;74 repeats,89 non-coding RNAs,24 gene islands,2 CRISPR sequences and 4 spacer sequences W-6 was also found to contain prophage,indicating that W-6 is a lysogen.The results of host resequencing alignment in different stages of co-evolution showed that a total of 254 base mutations were involved,involving 80 genes,of which the receptors related to the adsorption receptors reached 10% of the total number of mutations,while the outer membrane proteins were mutated.Much more than LPS;while methyl chemotactic mutations account for 10%,which may be related to the restriction modification system.PCR amplification experiments also found that LPS-related genes showed little change,while the outer proteins changed significantly,further confirming that the outer membrane protein plays a much larger role in adsorption than LPS.It has also been discovered that phage integrates its integrase genes into the host genome during the later stages of the co-evolution process.The changes in phage genome during co-evolution mainly occurred in two tail silk proteins,especially the tail silk protein GP28,while the hydrolase protein and perforin protein were almost unchanged.In vitro activity experiments showed that the heterozygous expression of the tail protein GP28 was active and could compete with phage to recognize the adsorbent receptor.Therefore,it is speculated that gp28 may be an important adsorption gene in the process of phage adsorption of the host.This study preliminarily revealed the role of adsorption sites and adsorption receptors in host-phage interactions,and explained the changes of host and phage during co-evolution,providing a basis for elucidating the phage-host hostile relationship.