Fungal cell-wall lytic enzymes, antifungal metabolite(s) production, and characterization fromStreptomyces exfoliatusMT9 for controlling fruit-rotting fungi

Abstract

An antifungal actinomycete strain MT9 was isolated from Loktak Lake, Manipur, India and its cultural characteristics, fatty acid methyl ester, 16S rRNA gene analysis suggests that strain MT9 is identical to Streptomyces exfoliatus. Strain MT9 displayed strong and broad-spectrum antagonism towards several fruit-rotting fungi by mycelial growth suppression. Crude fungal cell-wall lytic enzymes, i.e., chitinase, β-1,3-glucanase, and protease produced by S. exfoliatus MT9 were optimally active at pH 8.0 and 50 °C, pH 5.0 and 60 °C, pH 9.0 and 70 °C, respectively. All three mycolytic enzymes had good stability over a wide pH range of 5.0-10.0, with protease being more thermostable than both chitinase and β-1,3-glucanase. Interestingly zymogram analysis revealed that S. exfoliatus MT9 secretes six distinct chitinase isoenzymes with approximate molecular weights of 9.42, 13.93, 27.87, 36.43, 54.95, 103.27 kDa, six active protease isoenzymes with apparent molecular weights of 12.45, 30.20, 37.45, 46.32, 52.46, 131.46 kDa, and an active band of 119.39 kDa as β-1,3-glucanase enzyme. Extracellular fluid and its organic solvent extracts also exhibited inhibitory activity to various fruit-rotting fungi. The MIC value of n-butanol extract was 2-25 µg/ml against tested fruit-rotting fungi. Antifungal secondary metabolite(s) was found to be polyene in nature. To the best of our knowledge, this is the first report on extracellular production of fungal cell-wall lytic enzymes and antifungal metabolites by bioactive S. exfoliatus MT9 under submerged fermentation.

The ability of a cold-adapted Rhodotorula mucilaginosa strain from Tibet to control blue mold in pear fruit

“…The different biocontrol efficacy of these two species, however, was disparate, indicating something other than just competition for nutrients and the ability to grow at low temperature plays a role in their biocontrol activity. Differences between the two species in the level of activity of two enzymes (chitinase and b-1,3-glucanase) that have been reported to play an important role in biocontrol activity (Bautista-rosales et al 2014;Choudhary et al 2014;Lima et al 2013;Lutz et al 2013;Wang et al 2015), suggest that these enzymes may play a significant role in the differences observed in biocontrol activity at 4°C.…”

Biological control of toxigenic citrus and papaya‐rotting fungi by Streptomyces violascens MT7 and its extracellular metabolites

“…). As stated in many reports, extracellular production of secondary metabolites during stationary phase is related to the antibiosis toward pathogenic fungi . Broad spectrum antifungal potential of ECF of antagonist strain MT7 and its n ‐butanol extract indicates the presence of antifungal metabolite(s) in culture filtrate (Table ).…”

“…Ergosterol inhibition assay revealed the polyene type of extracellular antifungal metabolite(s) (Table ). Polyene antibiotics, e.g., nystatin or amphotericin B are known to have higher affinity toward egrosterol present in fungal cell‐wall thus causing micropores formation that disrupts the cell membrane function and hence leads to leakage of cellular constituents and fungicidal effect . The MIC values of the crude n ‐butanol extract in increasing order against C. gloeosporioides MTCC 9664, A. niger MTCC 281, G. candidum NFCCI 2848, R. stolonifer ITCC 5100, R. stolonifer NFCCI 2853, and Penicillium sp.…”

Diversity and antagonistic activity of endophytic fungi from sweet cherry and pepper

“…However, as low concentration of these substances are excreted by endophytes in host plant, the effects of antibiotics to pathogens In Vivo need to be assessed. As well, many microorganisms produce and release lytic enzymes that can hydrolyze a wide variety of polymeric compounds, including chitin, proteins, cellulose, hemi-cellulose and DNA DOI: 10.14267/phd.2015062 (Choudhary et al, 2014). When endophytes colonize on the plant surface, they produce enzymes to hydrolyze plant cell walls.…”

“…As a result, these enzymes also have the function to suppress plant pathogen activities directly and have the capability of degrading the cell walls of fungi and oomycetes. Although, the enzymes may not be of most importance in antagonism, they may contribute to antagonistic activity through a combination of mechanisms (Choudhary et al, 2014). Endophytic fungi are also thought to induce host resistance to pathogen by activating the plant natural defenses.…”