Abstract
The novel alkaliphilic strain, designated as Bacillus sp. IB-OR17 and isolated from soda lake sediments, was identified and characterized. Isolated strain demonstrated slight antifungal activity against some plant pathogen fungi that are capable to grow under alkaline conditions. Based on its morphological, physiological and biochemical characteristics as well as on 16S rRNA gene analysis data, Bacillus sp. IB-OR17 were related to alkaliphilic species B. mannanilyticus. Such as type species, Bacillus sp. IB-OR17 produced extracellular β-mannanase but additionally it displayed also chitinolytic activity which is a new property reported for this species. Bacillus sp. IB-OR17 grew in pH range 8.0 - 11.0 with maximal intensity under 9.0 - 10.0 but not showed halophilic properties (growth limit under NaCl concentrations Bacillus sp. IB-OR17 produced chitinase(s) in presence of colloidal chitin as main carbon source and sodium carbonate (0.25% - 1.0%) demonstrating high enzyme yield under enough low concentrations of the substrate (0.20%). Unlike chitinase, β-mannanase was constitutively produced by Bacillus sp. IB- OR17 in presence of various substrates including crab shell chitin. Probable involvement of the enzymes in antifungal activity of Bacillus sp. IB-OR17 is discussed shortly in terms of further researches and application of this strain.
Highlights
Alkaliphilic microorganisms attract increased attention during last decades in the context of their great potential for biotechnological applications and research of ecological diversity, physiologic, biochemical and molecular specifics of extremophiles in general [1]
Bacillus sp., strain IB-OR17, isolated from alkaline lake sediments displays a slight growth-inhibiting effect against some plant pathogenic fungi under testing on the nutritional agar medium containing 1% of D-glucose and 1% of sodium carbonate (Ph ~ 9.5 - 10.0). These conditions are not very favorable for typically neutrophilic soil fungi such as Bipolaris sorokiniana and Fusarium oxysporum growing here as separate small colonies rather than mycelial lawn, production of antifungal compounds by IB-OR17 was confirmed visibly (Figure 1)
IB-OR17 demonstrated its highest similarity to B. mannanilyticus A-001 and B. horti A62 species among eighteen of reference type-strains
Summary
Alkaliphilic microorganisms attract increased attention during last decades in the context of their great potential for biotechnological applications and research of ecological diversity, physiologic, biochemical and molecular specifics of extremophiles in general [1]. Amylases, lipases and cellulases, production of chitin-degrading enzymes by alkaliphilic bacilli are reported more scarcely [3] [4], this group together with other extremophiles can be considered as a promising source of chitinases and chitosanases characterized with new properties interesting for their biotechnological application. Chitinases being active and stable in alkaline interval of pH values are applicable in composting process of chitin-containing wastes in sea-food industry; especially, the enzymes combining alkaline pH-optima and high thermostability are most suitable for these purposes [5]-[7]. The isolate displayed slight growth-inhibiting activity against some soil-borne fungi under alkaline conditions. Later, it demonstrated capability of visible hydrolysis of colloidal chitin when it cultivated on agar alkaline media containing this substrate
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