Violacein is a biotechnologically significant secondary metabolite due to its antibacterial, antifungal, and other properties. Isolation, research, and identification of violacein producing strains are of interest for the development of biotechnological processes, in order to enhance the biosynthesis of this compound. The purpose of the present work was to study the properties of a newly isolated bacterium capable of synthesizing blue-purple pigment. An aboriginal bacterium was isolated from the coastal zone of the Vezelka River in the city of Belgorod. Based on chemical and spectrophotometric studies of the crude ethanol extract, the pigment was identified as violacein, and the isolate was assigned to the group of violacein-forming bacteria, which includes bacteria of the genera Chromobacterium, Iodobacter, Janthinobacterium, Duganella, Collimonas, and Massilia. Based on cultural, morphological, tinctorial, physiological, and biochemical properties, as well as analysis of the 16S rRNA gene sequence, the new isolated strain was assigned to the genus Janthinobacterium. The isolated strain is capable of suppressing the growth of a number of fungal and bacterial phytopathogens. For representatives of the genus Janthinobacterium, their inhibitory influence on cyanobacteria was shown for the first time.

A study of antifungal properties of violacein-forming strain Janthinobacterium sp. B-3515 as well as its secondary metabolite, violacein, against Alternaria brassicicola F-1864 is presented. Regardless of the presence of bacteria, mycelium growth in the first two days proceeded at the same rate. The effect of the bacterial strain was manifested after the third day of incubation. In general, during co-culture, the bacterial strain statistically significantly reduced the average growth of the mycelium of the mould fungus by 10%. The average growth of A. brassicicola F-1864 was decreased in the presence of an aqueous solution of violacein in the nutrient medium (1%, 3%, and 5%). The pigment in 5% concentration had the greatest effect, as the difference between the average growth of the control group and the experimental group was 18%. The mycostatic activity of bacteria of genus Janthinobacterium and violacein against mould fungus Alternaria brassicicola F-1864 was shown for the first time.

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The paper presents data on the evaluation of the antagonistic potential of Pseudomonas chlororaphis 3 and P. chlororaphis BS-1393 strains against the bacterium of the genus Ralstonia. It was revealed that the native strain is 30% more effective than the collection one. A scheme for obtaining an ethyl acetate extract of phenazine compounds, whose antibacterial activity exceeds the effectiveness of the extractant (ethyl acetate) by 57%, has been developed.