[Identification and Antagonistic Properties of the Soil Streptomycete Streptomyces sp. 100]

Determination of the taxonomic status of the soil streptomycete Streptomyces sp. 100 and study of its antagonistic properties against phytopathogenic and opportunistic human microorganisms.

For the identification of the strain a set of conventional methods morphological and cultural, physiological and biochemical characteristics of the producer, as well as molecular genetic analysis of 16S rRNA gene were used. Streptomycete was cultivated on agar nutrient and liquid soy medium until the stationary phase of growth. The antagonistic activity of the strain was studied by agar diffusion method.

The study of morphological and cultural properties showed that Streptomyces sp. 100 formed the colonies with irregular edges protruding from the depressed center, straight sporophores were short, gathered in whorls; spores were oval, smooth shell dispute. Growing on agar medium (pH 6.8-7.4, temperature 28 °C, microaerophilic conditions) this strain formed mycelium of various colors: the air white, white-yellow, white-brown or substrate tan, cream and yellow, creamy carmine, yellow-brown. A soluble pigment was yellow and yellow-brown, while melanoid pigment was not detected. The morphological, cultural, physiological, biochemical and molecular genetic characteristics of the soil streptomycete let to identify it as Streptomyces netropsis (Finlay et al., 1951) IMV Ac-5025 (UCM Ac-2186) that is an active antagonist IMV Ac-5025 against plant pathogens. Growing on a surface of agaric nutrient media it inhibits phytopathogenic bacteria (Xanthomonas axonopodis pv. glycines 8609, Pseudomonas savastanoi pv. glycinea 8571, P. syringae pv. coronafaciens 9030) and fungi (Alternaria alternata 16814, Fusarium оxysporum 54201) zone of growth inhibition were 20 - 32 mm and 16 - 30 mm respectively. The supernatant of culture medium and the ethanol extract of biomass inhibited the growth of pathogenic bacteria and fungi. The most sensitive to action of a supernatant of cultural liquid were P. syringae pv. atrofaciens 7886 and Clavibacter michiganensis ssp. michiganensis 102, growth inhibition zones - 42 and 30 mm respectively. It should be noted that in the majority of cases the supernatant of cultural liquid suppressed growth of phytopathogenic bacteria in comparison with biomass extract more actively. At the same time only biomass extract inhibited the growth of P. syringae pv. coronafaciens 9060, P. corrugatа 9070, X. anoxopodis pv. glycines 9075, X. anoxopodis pv. glycines 8609 and Pantoea agglomerans 8490. Tolerant to metabolites of S. netropsis IMV Ac-5025 were P. syringae pv. atrofaciens 8291 and X. visicatoriae 7790. The extract of biomass S. netropsis IMV Ac-5025 inhibited growth of all studied strains of phytopathogenic fungi (A. alternata 16814, A. culmorum 00790, F. оxysporum 54201, F. tricinetum 00795, F. oxysporum n.33, Cladosporium herbarum 16863, Cochliobolus spicifas 16860, Nigrospora oryzae 16864). The supernatant of the cultural liquid also showed the oppressing action on fungi, except for Cladosporium herbarum 16863 and Cochliobolus spicifas 16860. The strain was almost ineffective against opportunistic human microorganisms (Escherichia coli ATCC 25922, Bacillus pumilus NCTC 8241, Staphylococcus aureus FDA 209P et al.).

The lack of action of Streptomyces netropsis IMV Ac-5025 on the opportunistic human microorganisms and the active antagonism of phytopathogens, both, define potential its application for plant protection.