Antifungal Activity of Bacteria of the Genus Bacillus and Streptomyces Isolated from the Soil of the Republic of Moldova

Abstract

Aim. The article deals with the results of research, the aim of which was to determine antifungal activity of the strains Bacillus and Streptomyces genera, in relation to phytopathogenic fungi, widely distributed in Moldova. Methods. Strains were grown on classical agar media, the antifungal activity was determined by the method of agar blocks with test cultures -phytopathogenic fungi. Biological standard was the bacterium B. subtilis 26D. In the experiments on the germination of A. alternata conidia, 5 bacterial cultures grown in liquid nutrient medium No. 2. Results. It is established that all bacteria of genus Bacillus exhibit antifungal activity against test cultures, but in varying degrees. The growth of B. cinerea and F. oxysporum was least inhibited. Strain B. subtilis S4 most actively suppressed the growth of S. sclerotiorum. Strain Streptomyces sp. 10 is able to completely suppress the growth of A . alternata and B. cinerea, and the strain S. sp 9 completely suppressed the growth of S. sclerotiorum. Strains 9, 12, and 66 actively inhibited growth of F. culmorum (the radius of the zones was 16.0−20.0 mm), and strain S. sp. 185 against F. oxysporum (zones up to 28.0 mm). The strongest inhibitory effect on the germination of A. alternata conidia had strain S2. Conclusions. A comparative assessment of the antifungal activity of B. subtilis revealed a strain with the most pronounced antifungal properties. The investigated liquid cultures of bacteria of the genus Bacillus exhibited a special fungicidal effect on the germination of A. alternata conidia. Among 7 strains of streptomycetes tested, particular interest had S. sp. 10, capable to completely suppressing the growth of A. alternata and B. cinerea, and the strain S. sp. 9 -completely inhibits the growth of S. sclerotiorum, as well as the strain S. sp. 185 actively inhibited the growth of F. oxysporum and the strain S. sp. 10 − A. solani.

Studying Microbial Communities through Co-Occurrence Network Analyses during Processes of Waste Treatment and in Organically Amended Soils: A Review

“…This points towards a possible competition for resources among the bacterial and fungal members of the community, which can result in a selective competitive pressure on each other. Biological inhibition caused by the production of antimicrobial substances may be another factor leading to the occurrence of negative correlations over the course of the composting process [71]. The co-occurrence patterns of bacterial and fungal communities can also be altered by the presence of additives in the composting system.…”

Planifilum fulgidum Is the Dominant Functional Microorganism in Compost Containing Spent Mushroom Substrate

“…Meanwhile, the dominant microflora (Firmicutes, Actinomycetes) in the composts was beneficial to crop plants in eliminating pathogens (through the release of some antibiotics) and environmental stress tolerance (through the secretion of signal compounds) [15,16]. The antifungal and protease activities of dominant composting bacteria Bacillus can reduce the infection rate of bacterial wilt and other fungal diseases of tomatoes and cucumbers [17]. In order to maintain the beneficial microorganisms, tomato root could exudate lactic acid and hexanoic acid to favor the growth of Bacillus cereus [18].…”