Biocontrol of wood-rotting fungi withStreptomyces violaceusnigerXL-2

Abstract

During the previous decade, chitinases have received increased attention because of their wide range of applications. Chito-oligomers produced by enzymatic hydrolysis of chitin have been of interest in recent years because of their broad applications in medical, agricultural, and industrial applications, such as antibacterial, antifungal, hypo cholesterolemic, and antihypertensive activity, and as food quality enhancer. Fungal cell walls being rich in chitin also enable the use of chitinases in biocontrol of fungal pathogens, as bio-fungicides. An actinomycete was isolated from the bark of trees of Dehradun in India and was later identified as Streptomyces violaceusniger. This strain exhibits strong antagonism towards various wood-rotting fungi, such as Phanerochaete chrysosporium, Postia placenta, Coriolus versicolor, and Gloeophyllum trabeum. Further, studies showed an extracellular bioactive compound was responsible for the antagonism. The conditions for the production of this biocontrol agent were optimized, and the effects of various stress factors (like nitrogen-deficient media, carbon-deficient media, etc.) were studied. The presence of chitin in the growth media was found to be an essential factor for the active production of the biocontrol agent. The pH and temperature optima for the biocontrol agent were determined. Purification and characterization of this specific biocontrol agent was performed through anion exchange chromatography using a DEAE-cellulose column, and a single protein band was obtained on a 10% sodium dodecyl sulfate-polyacrylamide gel. The protein was later identified as a 28 kDa endo chitinase by MALDI-TOF (matrix-assisted laser desorption ionization-time of flight) and by a chitobiose activity assay.

Chitinases: An update

“…[2] Bacterial chitinases are active over a wide range of pH and temperatures, depending on the source of the bacteria from which they have been isolated. For example, endochitinase from Streptomyces violaceusniger [43] and thermostable chitinase from Streptomyces thermoviolaceus OPC-520[16] have an optimum temperature of, respectively, 28°C and 80°C. Also, the last enzyme has high pH optima in the range of 8.0 to 10.075, while the chitinase isolated from Stenotrophomonas maltophilia C3 has a pH optima in the range of 4.5 to 5.0.…”

Purification and Characterization of Chitinase Produced by Endophytic <i>St</i><i>re</i><i>ptomyceshygroscopicus</i><i> </i>Against Some Phytopathogens

“…Owing to the innocuous nature of these organisms, deliverysystems to introduce endophytic bacteria, such asStreptomyces spp., into plants have been developed, andthe potential for endophytes as biocontrol agents has beenexplo red [16]. In a recent study, [1]. Shekharet al [1]purified a bioactive compound from endophytic Streptomyces violaceusnigr that showed a strong antagonism towards various wood-rotting fungi, and chitinase enzymes wereassociated with this inhibition.…”

“…In a recent study, [1]. Shekharet al [1]purified a bioactive compound from endophytic Streptomyces violaceusnigr that showed a strong antagonism towards various wood-rotting fungi, and chitinase enzymes wereassociated with this inhibition. In general, the higherchitinase activity was correlated with h igher fungalinhibit ion.…”

“…Microbial antagonists are widely used for the b iocontrol of fungal plant diseases [1]. Endophytic micro-organis ms have receiv ed cons iderab le atten tion fo r th eir poten tial as biocontrol agents of fungal p lant pathogens.…”

Rhizospheric streptomycetes as potential biocontrol agents of Fusarium and Armillaria pine rot and as PGPR for Pinus taeda

“…Although several authors have shown the effectiveness of these microorganisms as biological plant disease control agents (Shekhar et al 2006;Lehr et al 2008), very few reports involve forest species (Lehr et al 2007).…”