Antifungal chitinases from Bacillus pumilus SG2: preliminary report

Abstract

A halotolerant bacterium capable of chitinase production was previously isolated from saline soils of Gavkhooni marsh, Iran. The strain was identified as Bacillus pumilus strain SG2. This strain secretes two chitinases into the medium in response to the presence of chitin in the medium. The two chitinases, ChiS and ChiL, were active on both polymeric as well as oligosaccharide substrates. In this study, these two extracellular chitinases were purified from the supernatant of the Bacillus culture by ammonium sulfate precipitation. The optimum pH and temperature for both of these chitinases were pH 6 and 37°C, respectively. According to the conserved domain analysis, ChiS and ChiL were categorized in family 18 of the glycosylhydrolases. Three essential conserved amino acid residues in in ChiL were found within the active site. Antifungal activities of the two purified chitinases were assessed on Rhizoctonia solani, Verticillium sp., Nigrospora sp., Stemphyllium botryosum and Bipolaris sp. demonstrating inhibition of all the tested strains. However, these chitinases did not inhibit cell wall formation of the non-chitin-containing fungi (oomycetes) Phytophthora citricola and Phytophthora capsici. This is the first investigation demonstrating antifungal activity of chitinases purified from B. pumilus SG2.

Chitinolytic Microorganisms and Their Possible Application in Environmental Protection

“…R. solani , Aspergillus niger (NCIM 563), Aspergillus , Rhizopus , Mucor sp.[4, 70, 75] Trichoderma atroviride PTCC5220 Rhizoctonia solani [39] Trichothecium roseum Alternaria alternata , Fusarium moniliforme, Magnaporthe grisea [22] Basidiobolus ranarum Rhizoctonia solani , F. solani .[68] Bacillus sp. BG-11 Rhizopus arrhizus , Sclerotium rolfsii , R. solani, Phytophthora infestans , F. oxysporum , Phanerochaete chrysosporium [7] Bacillus cereus YQQ 308 Fusarium oxysporum , F. solani , P. ultimum [11] Bacillus pumilus SG2 Fusarium graminearum , R. solani , Magnaporthe grisea , Sclerotinia sclerotiorum , Trichoderma reesei , B. cinerea , Bipolaris sp.[28] Bacillus cereus IO8 Botrytis cinerea [36] Bacillus thuringiensis subsp. colmeri 15A3 Rhizoctonia solani , B. cinerea , P. chrysogenum , P. piricola , Penicillium glaucum , Sclerotinia fuckelian [61] Brevibacillus laterosporus Fusarium equiseti [81] Aeromonas hydrophila SBK1 Aspergillus flavus , F. oxysporum [35] Enterobacter sp.…”

Purification and characterization of Streptomyces albidoflavus antifungal components

“…Jankiewicz et al [24] obtained 6 fold purified chitinase from Stenotrophomonas maltophilia with relatively high recovery of activity of 23%. Many researchers reported that bacterial chitinase belongs to the family of 18 glycoside hydrolases [22,25,26].…”

“…The molecular mass of the purified chitinase from Thermomyces lanuginosus SY2 was estimated to be 48 kDa by SDS PAGE [27]. Kim et al [25] reported that the molecular weight of the purified enzyme from Serratia sp. KCK was approxi mately 61 kDa.…”

Evaluation of rhizobacterial isolates from Argentina, Uruguay and Chile for plant growth-promoting characteristics and antagonistic activity towards Rhizoctonia sp. and Macrophomina sp. in vitro

“…Bacillus pumilus strain SG2 secretes two chitinases with antifungal activity [61]. Species of Pseudomonas have been known to excrete chitinases and b-1,3-glucanases to digest the fungal cell wall chitin and glucan respectively and use these as a carbon and energy source [62] and are also reported to produce wide range of antifungal metabolites [63,64].…”