Pseudomonas fluorescens SF4c produces two types of retractable tailocins

LOPEZ RAMIREZ, V; ASCONAPE, J; RUIZ, M; ROSSI, E; BONAMICO, N; FISCHER, S

virtual

Congreso; IV Reunión conjunta de Sociedades de Biología de la República Argentina; 2020

Sociedades de Biología de la República Argentina

Microorganisms in the rhizosphere produce metabolites, including bacteriocins, which allow them to compete for a specific niche. Bacteriocins antagonize bacteria which are phylogenetically related to the producing strain. Bacteriocins showing structural similarities with bacteriophage tails are known as tailocins. The native Pseudomonas fluorescens SF4c strain produces two tailocins (type R and type F). R tailocin has a common ancestor with the tail of Enterobacteriophage P2 of the Myoviridae family, while the same is true for type F with phage lambda of the Siphoviridae family. A F tailocin mutant derived from P. fluorescens SF4c was previously constructed in our laboratory. The present work aimed to construct a mutant in R tailocin and to compare them to each other. Primers were designed to amplify two fragments corresponding to the beginning and the end of the region that comprises the structural genes of R tailocin. Thus, 12000 bp of the cluster were deleted and replaced by a kanamycin gene. The antimicrobial activity of the R and F mutants was analyzed against different strains of the genera Pseudomonas and Xanthomonas. F tailocin inhibited 7 of the 8 strains tested, including Xanthomonas vesicatoria Xcv Bv5-4a which causes tomato and pepper spot disease, while R tailocin showed antimicrobial activity only against P. fluorescens CTR212. Thus, F tailocin had a wider killing spectrum. Therefore, it could be used in the future as a tool to control spot disease. A phylogenetic study of P. fluorescens SF4c bacteriocins was also performed. The structural genes of each SF4c tailocin were aligned using MEGA software with those of tailocins produced by other plant-associated Pseudomonas. Furthermore, EDGAR software was used to analyze the average amino-acid identity matrix (AAI) and to generate a Venn diagram of the orthologous gene cluster. Phage prediction was carried out on PHASTER software with the structural gene sequences for R and F tailocins. These bioinformatic analyses showed that F tailocin was grouped with R-type tailocins from others plant-associated Pseudomonas. Likewise, the prediction of related phages indicated identity with bacteriophages of the Myoviridae family, which have long retractable tails. In conclusion, the results suggest that P. fluorescens SF4c produces two types of retractable tailocins, called R1 and R2, with different spectra of action. An orthologous gene analysis could help to understand the phylogenetic evolution of these elements and their distribution in nature.