Out of the 30 actinobacterial cultures screened for antimicrobial activity, 28 cultures were found to produce active products against various pathogenic microorganisms such as Gram-negative, Gram-positive bacteria and yeast, using a modified cross streak method. The modified method helped in easy quantification of results and also in ruling out probable mutual antibiosis. The actinobacterial strains that showed the ability to produce antimicrobial compounds belonged to Streptomyces (53%), Micromonospora (13%) and Actinomadura (10%) genera. Streptomyces sp. strain MMA-5 showed the highest multispecific antibiosis efficiency score value. Broad antibiotic spectrum activity was exhibited by Streptomyces sp. strain MMA-2 and Micromonospora sp. strain MMA-8. The multidrug resistant human pathogenic yeast strain Candida albicans was inhibited by 18 actinobacterial strains.
New molecule discovery from natural sources, such as that of actinobacteria, has proved to be an interesting area in antibiotic research, as most of these antibiotics are difficult to synthesize. Out of 30 actinobacterial cultures screened for antimicrobial activity, 28 cultures were found to produce active products against various pathogenic microorganisms such as Gram-negative, Gram-positive bacteria and yeast, using a ‘modified cross streak method.' The modified method helped in easy quantification of results and also in ruling out probable mutual antibiosis. 53%, 13% and 10% of tested actinobacterial strains belonging to Streptomyces, Micromonospora and Actinomadura genera, respectively, showed the ability of producing antimicrobial compounds. Streptomyces sp. strain MMA-5 showed the highest percentage multispecific antibiosis efficiency score value. Broad antibiotic spectrum activity was exhibited by Streptomyces sp. strain MMA-2 and Micromonospora sp. strain MMA-8. The multidrug resistant human pathogenic yeast strain Candida albicans was inhibited by 18 actinobacterial strains.
High frequency isolation of actinomycetes poses a challenge for the taxonomists hence simple and rapid identification methods are required. Our work to catalogue biodiversity of actinomycetes of Goa yielded several distinct morphotypes. After their tentative identification, the feasibility to distinguish these using digital image analyses (DIA) was explored. Digital images of wild colony morphotypes were processed using public domain SCION image analysis software. DIA revealed some intricate digital characters. A combination of these with standard morphological and microscopic characters could be potentially useful for preparing a digital identification key of the actinomycetes strains with potential application in rapid taxonomic identification.
High frequency isolation of actinomycetes poses a challenge for the taxonomists hence simple and rapid identification methods are required. Our work to catalogue biodiversity of actinomycetes of Goa yielded several distinct morphotypes. After their tentative identification, the feasibility to distinguish these using digital image analyses (DIA) was explored. Digital images of wild colony morphotypes were processed using public domain SCION image analysis software. DIA revealed some intricate digital characters. A combination of these with standard morphological and microscopic characters could be potentially useful for preparing a digital identification key of the actinomycetes strains with potential application in rapid taxonomic identification.
Soils are known to be ultimate and complex reservoirs of microbial diversity. The complex dimensions of bacterial and fungal diversity in tropical soils and microbial community dynamics are underexplored. Isolation techniques aimed at Actinomycetes generally employ highly selective media, powerful antibiotics and antifungal compounds to suppress undesirable bacteria and fungi. However some soil fungi may show their resistance towards these antifungal compounds. During our work to explore soil actinomycetes diversity, slides coated with Arginine Vitamin agar (AVA) incorporating a cocktail of antibiotics and antifungal compounds such as Nystatin, Cycloheximide, Terbinafin, Griseofulvin, and Fluconazole were exposed to soil environment and were retrieved at intervals of 4, 7, 15 and 28 days for detail microscopic studies of surface colonies. Along with actinomycetes the presence of unidentified aseptate and septate fungi was revealed indicating their resistance to combination and concentration of antifungals. Heat treatment of the soil was found to cause considerable decrease in fungal contamination probably due to elimination of heat labile fungi. Our results have led us to develop a simple procedure to sample the interesting and industrially useful strains of soil fungi resistant to common antifungal compounds. Some fungal strains are reported resistant to certain antifungals with resulting therapeutic failures as use of these antifungals inevitably selects resistant fungi, thereby pressing the urge for continuing and cyclical need of new antifungals (Augustin et al., 2004). This technique could prove useful to detect novel antifungal resistant strains with potential to emerge as novel human pathogens. It has not escaped our notice that the probability of such finding could also help to verify whether these fungi could utilize such antifungal compounds through use of hitherto undiscovered metabolic pathways and novel enzymes leading to identification of genes responsible for antifungal resistance.
An antibiotic produced by strain Streptomyces parvulus showing activity against Staphylococcus citreus was subjected to various optimization parameters for enhancing its production. Nutritional and physiological parameters produced by S. parvulus under shaken flask conditions were determined. Optimization of these parameters led to 11% increase in antibiotic activity with a mean zone of inhibition of 42 mm.Highest antibiotic production was obtained at 250 rpm for 14 days with optimum temperature of 28°C and pH 7. Kuster#x2019;s modified medium containing glycerol 0.7% (v/v), casein 0.03% (w/v), NaCl 0% (w/v), phosphate 0.25% (w/v), KNO3 0.1% (w/v) and CaCO3 0.0015% (w/v) concentration was found ideal.
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