Keratinases play an important role in biotechnological applications such as improvement of feather meal, enzymatic dehairing and production of amino acids or peptides from high molecular weight substrates. Bacillus subtilis P13, isolated from Vajreshwari hot spring (45-50 degrees C) near Mumbai, India, produces a neutral serine protease and has an optimum temperature of 65 degrees C. This enzyme preparation was keratinolytic in nature and could disintegrate whole chicken feathers, except for the remnants of shafts. The enzyme preparation also exhibited depilation of goat hides with the recovery of intact animal hair. The enzyme preparation could release peptides from ground feathers and bring about their weight reduction; however, similar action on hair was relatively weak. A single major PMSF-sensitive protease band could be detected upon zymogram analysis, indicating that a single enzyme may be responsible for feather degradation and hide depilation. The importance of these findings in the biotechnological application for feather and leather industries is discussed.
Isolation of five ionizing radiation (IR)-resistant bacteria by screening of isolates from various habitats classified as common and stressed is reported. IR-resistant isolates exhibited varying degrees of resistance to gamma-radiation and were classified as highly and moderately radiation resistant. Resistance to ultraviolet (UV) radiation correlated well with gamma-radiation resistance, whereas a comparable desiccation resistance for all the highly and moderately radiation-resistant isolates was observed. However, salt tolerance failed to correlate with IR resistance, indicating a divergent evolution of the salt tolerance and radiation resistance. Characterization of isolates by the amplified rDNA restriction analysis profiling attested to the clustering of these isolates with their stress phenotype. 16S rRNA gene-based analysis of the isolates showed that the bacteria with similar-resistance physiologies clustered together and belonged to related genera. Hydrogen peroxide resistance and mitomycin survival patterns of the isolates indicated the roles of oxidative-stress tolerance in desiccation survival and recombination repair in higher radiation resistance, respectively.
The Streptomyces spp. used in this work were previously isolated as diazotrophic endophytes from sorghum stems. Here, we characterized the Streptomyces spp. for their colonization ability, plant growth promotion and protection against fungal disease in three cereals. In vitro analysis by dual culture study showed inhibitory effect on the rice pathogen Magnaporthe oryzae B157 along with inhibition of the ubiquitous phytopathogen Rhizoctonia solani by the Streptomyces spp. used in this study. The active compounds responsible for phytopathogen inhibition were extracted with ethyl acetate and tested positive against the fungal pathogens. GC-MS based identification of the active compounds responsible for fungal pathogen inhibition showed them to be 2-(chloromethyl)-2-cyclopropyloxirane, 2, 4- ditert-butylphenol and 1-ethylthio-3-methyl-1, 3-butadiene in extracts of culture supernatants from the three different strains respectively. EGFP tagged Streptomyces strains showed profuse colonization in roots as well as aerial parts of cereal plants. Direct inhibitory action against M. oryzae B157 and R. solani correlated with the observation that upon fungal pathogen challenge, the bacterized rice, sorghum and wheat plants showed significantly good plant growth, particularly in aerial parts as compared to unbacterized controls. In addition, benefit was seen in inoculated healthy plants in terms of increase in wet weight of roots and shoots as compared to the uninoculated controls. The mechanism of biocontrol also involved induction of plant defense response as evidenced by the upregulation of PR10a, NPR1, PAL and LOX2 in Streptomyces colonized plants.
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