The current work was carried out under a screening program targeted at isolation of bioactive Streptomyces species from soil samples. A total of 54 Streptomyces species were isolated from soil samples, out of which 4 isolates were found to be promising. These isolates were identified as Streptomyces spectabilis, Streptomyces purpurascens, Streptomyces coeruleorubidus and Streptomyces lavendofoliae and their sequences have been deposited in the GenBank. The influence of culture conditions including, incubation time, incubation temperature, initial pH and different carbon and nitrogen sources on growth and bioactive compound formation was investigated. Isolate R1, identified as Streptomyces spectabilis, showed maximum bioactive metabolite production with cellobiose and peptone as the carbon and nitrogen sources, on the 5 th day at pH 5 at 30˚C. The optimum conditions for production by isolate R3, identified as Streptomyces purpurascens, were observed to be starch and casein as the carbon and nitrogen sources, pH 7, temperature 30˚C and an incubation period of eight days. For isolate R5, identified as Streptomyces coeruleorubidus, maximal production resulted on the sixth day at pH 6 and temperature of 35˚C with mannitol and JBM. Isolate Y8, identified as Streptomyces lavendofoliae, was found to produce high levels of bioactive metabolites in the medium supplemented with starch and peptone on the 10 th day at pH 7 and at an incubation temperature of 30˚C. The four strains tested here behaved differently, each one requiring specific conditions for maximum growth as well as bioactive metabolite production.

Bacteriological analysis of the water samples collected from upstream, midstream and downstream points along the bank of the river revealed high populations of Escherichia coli, Citrobacter freundii, Citrobacter diversus, Enterobacter aerogens and Klebsiella species. All these isolates were screened against eight antibiotics to determine the prevalence of multiple antibiotic resistance among isolates at different sites of the river. The study revealed that multiple antibiotic resistance was prominently seen in coliforms at downstream sites (Average multiple antibiotic resistance index, MAR Index = 0.43) while it was low in coliforms at upstream sites (MAR Index = 0.15). These differences in MAR indices provide a method for distinguishing high risk contamination sites in aquatic environment.

Hyperthermostable alkaline lipase from Bacillus sonorensis 4R was purified and characterized. The enzyme production was carried out at 80°C and 9.0 pH in glucose-tween inorganic salt broth under static conditions for 96 h. Lipase was purified by anion exchange chromatography by 12.15 fold with a yield of 1.98%. The molecular weight of lipase was found to be 21.87 KDa by SDS-PAGE. The enzyme activity was optimal at 80°C with t 1/2 of 150 min and at 90°C, 100°C, 110°C, and 120°C; the respective values were 121.59 min, 90.01 min, 70.01 min, and 50 min. The enzyme was highly activated by Mg and t 1/2 values at 80°C were increased from 150 min to 180 min when magnesium and mannitol were added in combination. The activation energy calculated from Arrhenius plot was 31.102 KJ/mol. At 80–120°C, values of ΔH and ΔG were in the range of 28.16–27.83 KJ/mol and 102.79 KJ/mol to 111.66 KJ/mol, respectively. Lipase activity was highest at 9.0 pH and stable for 2 hours at this pH at 80°C. Pretreatment of lipase with MgSO4 and CaSO4 stimulated enzyme activity by 249.94% and 30.2%, respectively. The enzyme activity was greatly reduced by CoCl2, CdCl2, HgCl2, CuCl2, Pb(NO3)2, PMSF, orlistat, oleic acid, iodine, EDTA, and urea.

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During a screening program for bioactive natural products, a potential Streptomyces sp was isolated from soil. On the basis of biochemical, cultural, physiological and 16S rRNA gene analysis, it was identified as Streptomyces purpurascens. The isolate was grown in liquid medium and the crude antibiotic complex was obtained by ethyl acetate extraction. Seven purified fractions were obtained by preparative Thin Layer Chromatography (TLC). Acid hydrolysis of each fraction and subsequent TLC led to the identification of aglycones and sugars indicating these compounds to be Rhodomycin and its analogues. The identity of these compounds was established on the basis of UV-visible and FT-IR spectra and comparison with published data. The compounds were active against Gram-positive bacteria. Compound E, identified as Rhodomycin B, was found to be the most potent compound with an MIC of 2 μg/ml against Bacillus subtilis. Compounds A and F identified as α2-Rhodomycin II and Obelmycin respectively, and Compound E exhibited an IC50 of 8.8 μg/ml against HeLa cell line but no cytotoxicity was found against L929.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-93) contains supplementary material, which is available to authorized users.