Microbiological and genetic characteristics of Bacillus velezensis bacillibactinproducing strains and their effect on the sulfate-reducing bacteria biofilms on the poly(ethylene terephthalate) surface

Abstract

It was evaluated the antibiofilm-forming properties of NUChC C1 and NUChC C2b isolates (from the collection of the Department of Biology of the T.H. Shevchenko National University “Chernihiv Colehium”) against the sulfate-reducing bacteria biofilms on the poly(ethylene terephthalate) surface. NUChC C1 and NUChC C2b isolates were isolated by classical microbiology methods on Postgate’s “B” medium and their cultural-morphological, some physiological-biochemical properties and molecular-genetic characteristics were investigated. To identify bacteria the sequencing and analysis of the 16S rRNA gene were carried out. The bacteria were identified as Bacillus velezensis. Based on PCR-ISSR analysis, it was found that the studied bacteria belong to different strains. The 16S rRNA gene sequences were submitted in GenBank as MN508954.1 (NUChC C1), MN749356.1 and MN749357.1 (NUChC C2b). In the genome of B. velezensis the presence and transcriptional activity of the genes for the synthesis of bacillibactin (dhbC, dhbF), fengycin (fenA) and polyglutamic acid (epsK) were studied. Among these only genes belonging to bacillibactin synthesis operon were detected and only they demonstrated activity. The observed mode of dhbC and dhbF genes expression during 144 hours of cultivation differed between two B. velezensis strains: gradually increasing in NUChC C1 and sharply increased after 24 hours with decreasing on 144th hour in NUChC C2b. Antagonistic properties of the studied strains of B. velezensis against sulfate-reducing bacteria Desulfovibrio oryzae NUChC SRB1 and NUChC SRB2 were not observed. Siderophore-producing strains of Bacillus velezensis inhibit the formation of bacterial biofilms on the polymeric material poly(ethylene terephthalate) during its long-term exposure (50 days) in a culture of sulfate-reducing bacteria under conditions of sufficient iron supply. Bacillibactin-producing strains prevent the development of bacterial biofilms on the poly(ethylene terephthalate) surface. This is one of the reasons for the prolongation of the process of poly(ethylene terephthalate) biodegradation in natural ecosystems.