Citation: Moaz M. Hamed, Lamis Sh. Abdelfattah and Nayer M. Fahmy, Antimicrobial Activity of Marine Actinomycetes and the Optimization of Culture Conditions for the Production of Antimicrobial Agent(s), J Pure Appl Microbiol., 2019; 13(4):2177-2188. Abstract The aim of the present study was to isolate antagonistic actinomycetes from marine sediment collected from the Red Sea coast at Hurghada city and the Suez Gulf. A total of 16 actinomycete isolates were obtained in October 2018 and their antagonistic activities were evaluated against Aeromonas hydrophila, Vibrio damsela, Staphylococcus aureus ATCC6538, Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa ATCC 9027, Salmonella typhimurium ATCC 14028, Escherichia coli ATCC 19404 and Candida albicans ATCC 10231 by using the agar well diffusion method. Among the 16 isolates, 14 (87.5%) isolates exhibited antimicrobial activity against most of the tested pathogens. The most potent isolate was identified by 16S rRNA sequence analysis as Streptomyces sp. and designated Streptomyces sp. MK388207. The experimental design of Plackett-Burman was implemented to optimize the culture conditions for antimicrobial agent(s) production by the most powerful isolate against C. albicans ATCC 10231 when grown in starch nitrate broth and the data revealed that negative (-) levels of KNO 3 , K 2 HPO 4 and pH and positive (+) levels of starch, MgSO 4 .7H 2 O, FeSO 4 and incubation period supported the production of the antimicrobial agent(s). Growth under the optimized culture conditions led to a 1.4-fold rise in antimicrobial activity. The ethyl acetate extract of Streptomyces sp.MK388207 was subjected to gasliquid chromatography mass spectrometry (GC MS) and revealed the presence of six fractions with the major component being phenol, 2,4-bis (1,1 dimethylethyl). The findings of this study suggested that the antagonistic marine Streptomyces, in particular Streptomyces sp MK388207, the antibacterial compounds produced by this isolate, could be used as antibiotics that could have future applications in the pharmaceutical industry.
Ten sediment samples were gathered from several geographical locations around mangrove habitat, Red Sea coast, Egypt, during summer 2019. Actinobacteria are widespread in most mangrove soil samples. The average actinomycetes counts in sediment samples were ranged from 4 to 15 CFUg-1, also physico-chemical characters for soil samples were determined. Statistical analysis was applied to assess if the geographical location and physico-chemical characters influenced the communities of actinomycetes. A total of 10 actinomycetes were isolated and characterized physiologically and biochemically. The antimicrobial activities of different actinomycetes isolates were assessed. Isolate M3 was chosen as the most promising isolate with broad antagonistic activity against Bacillus subtilis ATCC 6633, Escherichia coli ATCC 19404, Staphylococcus aureus ATCC6538, Pseudomonas aeruginosa ATCC 9027, and Candida albicans ATCC 10231 with inhibition zones ranged from 12.0 ± 0.9 to 20.0 ± 1.9 mm. Genotypic characterization of isolate M3 was made using 16S rDNA sequence analysis and identified as Streptomyces mutabilis M3 with accession number MT483919. This strain exhibited anticancer activity against breast cancer cell line (Mcf7), liver cancer cell line (HepG2) and colon cancer cell line (HCT116) and the IC50 values were 324.77, 333.71 and 354.46, respectively. Streptomyces mutabilis M3 MT483919 had high bio-flocculating activity for seawater treatment, and the recovery of the samples ranged between 71.97 and 76.05%. The crude extract of Streptomyces mutabilis MT483919 M3 was analyzed by Fourier transform infrared spectrum (FT-IR) and Gas chromatography-mass spectrometry (GC-MS).
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