Molecular genetic analysis of determinants defining synthesis of 2,4-diacetylphloroglucinol by Pseudomonas brassicacearum BIM B-446 bacteria

Based on a full-sized sequence of the genome of Pseudomonas brassicacearum BIM В-446 bacteria, we determined the nucleotide sequence of the locus encoding the synthesis of the 2,4-diacetylphloroglucinol antibiotic. It was shown in the limits of a nucleotide sequence with 9087 bp size to be localized at open reading frames homologous (96–99% identical residues) to structural ( phl A, phl C, phl B, phl D, phl E, and phl I) and regulatory ( phl F, phl G, and phl H) genes of Pseudomonas brassicacearum and Pseudomonas fluorescens bacteria, which determine the production of 2,4-diacetylphloroglucinol. It emerged that closely related phl -operons differ by their environment. Thus, different genes were localized on the 3'-end. It was determined that inactivation of the phl A gene in P. brassicacearum BIM bacteria caused a loss of the ability to synthesize antibiotic and inhibited the growth of the phytopathogenic Fusarium culmorum , F. oxysporum , and Botrytis cinerea fungi; the antimicrobial activity was also decreased toward with fungal ( Alternaria alternate ) and bacterial pathogens ( Pseudomonas syringae and Pectobacterium carotovorum ). During inactivation of the phl F regulatory gene, which determines the synthesis of the phl -operon transcription repressor, the production of 2,4-diacetylphloroglucinol was increased. In contrast to the wild-type bacteria, phl F-mutants synthesized an antibiotic that was found in cultural liquid after 12 h of cultivation; its content reached the maximum in medium with saccharose as the carbon source.