AUTHOR=Riera Nadia , Davyt Danilo , Durán Rosario , Iraola Gregorio , Lemanceau Philippe , Bajsa Natalia 

TITLE=An antibiotic produced by Pseudomonas fluorescens CFBP2392 with antifungal activity against Rhizoctonia solani

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1286926

DOI=10.3389/fmicb.2023.1286926

ISSN=1664-302X

ABSTRACT=<p><italic>Pseudomonas fluorescens</italic> CFBP2392 has been recognized as a potential biocontrol agent due to its ability to suppress damping-off and root rot disease. This isolate has antibacterial activity <italic>in vitro</italic> as many other strains from the <italic>Pseudomonas fluorescens</italic> complex. In this work, the antibacterial and antifungal activity of the strain were explored. Dual culture assays evidenced the antifungal activity of the strain against different phytopathogens: <italic>Alternaria</italic> sp., <italic>Pythium ultimun</italic>, <italic>Fusarium oxysporum</italic>, and <italic>Rhizoctonia solani</italic>. Purification of an antifungal fraction was performed by preparative HPLC from the chemical extraction of growth media. The fraction showed altered <italic>R. solani</italic> growth and ultrastructure. Transmission electron microscopy revealed the purified compound <italic>induced</italic> hypertrophied mitochondria, membranous vesicles, and a higher number of vacuoles in <italic>R. salani</italic> cytoplasm. In addition, co-cultivation of <italic>P. fluorescens</italic> CFBP2392 with <italic>R. solani</italic> resulted in an enlarged and deformed cell wall. To gain genomic insights on this inhibition, the complete genome of <italic>P. fluorescens</italic> CFBP2392 was obtained with Oxford Nanopore technology. Different biosynthetic gene clusters (BGCs) involved in specialized metabolites production including a lokisin-like and a koreenceine-like cluster were identified. In accordance with the putative BGCs identified, sequence phylogeny analysis of the MacB transporter in the lokisin-like cluster further supports the similarity with other transporters from the amphisin family. Our results give insights into the cellular effects of the purified microbial metabolite in <italic>R. solani</italic> ultrastructure and provide a genomic background to further explore the specialized metabolite potential.</p>