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The current study aimed to isolate xylanase-producing marine actinobacteria, which is a novel idea; ascribed to the challenges associated with the culturing of marine microorganisms. A total of 5 actinobacterial colonies were isolated from Kanyakumari marine sediments. Among them only one isolate, A1 indicated the elevated xylanase activity manifesting a zone of hydrolysis of around 20 mm during primary screening. On the other hand, secondary screening of A1 i.e., sugar estimation by 3,5-dinitrosalicylic acid method, resulted in A1 exhibiting 400 µg/ml of enzyme activity. The enzyme extracted from the isolate A1 also contained a protein concentration of 600 µg/ml. Physical and chemical mutation studies were carried out to over-express xylanase production. Chemical mutation involving the use of EDTA did not show a significant increase in xylanase production and thus, was not subjected to further analyses. The isolate, A1 also showed a zone of hydrolysis of 28 mm in the physical mutation study and was named A'1.75. This zone was 8 mm more than the wild-type strain after UV-exposure for 75 min. A'1.75 also exhibited an enzyme activity of 600 µg/ml and protein content of 800 µg/ml. The potential isolate was identified as Streptomyces variabilis VITMUVB02 using 16S rRNA molecular sequencing. The molecular weight of the purified xylanase extracted from A1 and A'1.75 was found to be 25 kDa and 20 kDa, respectively. Fourier Transform Infrared spectroscopy (FT-IR) and High-Performance Liquid Chromatography (HPLC) analyses showed the mutagenic effect with the change in the spectral and functional groups. [ABSTRACT FROM AUTHOR]

A total of 192 different Streptomyces isolates were recovered from 34 soil samples collected from different localities in Egypt. The cytotoxic activities of culture supernatant of each of the recovered isolate were investigated against Caco-2 cell line using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The Streptomyces isolate coded S19, that showed the highest cytotoxic activity against Caco-2 cell line (CD50 of 26.4 µg/mL), was identified using 16S rRNA gene sequence analysis as Streptomyces variabilis isolate MW091521. The influence of cultural parameters affecting the cytotoxic activity of the respective isolate including the different culture media, initial pH value, temperature and rotation speed was investigated. A maximum cytotoxic activity (CD50 of 13.4 µg/mL) was obtained using the culture medium of soybean meal at an initial pH of 7.0, incubation temperature 28°C and 200 rpm. Thereafter, the fermentation was conducted in a 14 L laboratory fermenter under the previously stated optimum conditions with the aim of extraction, and purification of cytotoxic metabolite(s). Fractionation of the ethyl acetate extract followed by advanced spectroscopic analysis using LC/ESI/MS as well as 1D and 2D NMR experiments yielded the cytotoxic metabolite heliomycin. To the best of our knowledge, this is the first report on the production of heliomycin by Streptomyces variabilis isolate MW091521. [ABSTRACT FROM AUTHOR]

Streptomyces variabilis strain RD5, a marine actinomycete was isolated from Gulf of Khambhat and was employed to degrade, a model polycyclic aromatic hydrocarbon, phenanthrene. S. variabilis strain RD5 degraded (50 mg/L phenanthrene within 6 d) and the degradation was confirmed using the different analytical techniques. The phenanthrene biodegradation resulted in the formation of carbonochloridic acid ethyl ester, ethanol and acetone which were found in the mass spectral profile of the recovered degradation products. The plant seeds of Phaseolus mungo did not exhibit any growth inhibition when irrigated with the products of degradation. [ABSTRACT FROM AUTHOR]

Most immunosuppressive agents were initially developed as antibiotics produced by the genus Streptomyces. This investigation was devoted to explore the bioactive metabolite of the Streptomyces variabilis ASU319 extract and testing the purified active compound of this extract as an immunosuppressive agent in rats blood. Elucidation of the chemical structure and optimization of the active compound were studied as well. Antimicrobial activity was conducted using agar-well diffusion and disc diffusion assays. The antimicrobial metabolite was extracted from the fermentation broth by ethyl acetate and purified by TLC and silica gel column chromatography. The pure active compound was then subjected to spectroscopic analyses: 1H NMR, Elemental analysis, IR and Mass spectra. The active antimicrobial compound was tested as an immunosuppressive agent by injection in the rat blood and the complete blood count (CBC) was determined. The crude extracts of the selected active antagonistic five isolates were tested to prevent the inflammation and proliferation of lymphocytes of the rats blood. The active antimicrobial compound of Streptomyces ASU319 was purified and proven as an immunosuppressive agent. The tested compound decreased each of the neutrophils, lymphocytes and monocytes than the positive control. The compound was of molecular weight 458 g/mol and had given the proposed chemical formula C24H46O8. The most potent bacterial isolate was identified by 16SrRNA sequencing as Streptomyces variabilis ASU319 with accession number [GenBank: KC145278]. These results revealed that Streptomyces variabilis ASU319 is potential microbial for production of active antimicrobial compound that has the ability to decrease the proliferation of the lymphocytes cells in the blood and may be a good immunosuppressive agent. [ABSTRACT FROM AUTHOR]