Isolation and Importance of Endophytic Actinomycetes of Some Red Sea Algae and their Biological Activities

Endophytic Actinomycetes attract scientist's attention and in particular, endophytes from marine algae were documented and showed many biological activities that maintain ecological balance in various habitats that solve many health problems. This research aimed at the development of antimicrobial and antioxidant agent from endophytic Actinomycetes. Three seaweed algal samples were collected from the Red Sea Umluj corniche, nestled in northwestern of Saudi Arabia and identified as Ulva lactuca (Chlorophyta), Dictyota dichotoma (Phyaephyta) and Gelidium sp. (Rhodophyta). The collected algal samples were washed, surface sterilized, cut into small squares for Endophytic Actinomycete isolation on Starch nitrate medium containing 10% NaCl. Twelve actinomycetes were isolated, purified and screened for antimicrobial activities against four different Gram-positive bacterial pathogens in addition to Candida albicans as test organisms. Five isolates belonging to genus Streptomyces showed excellent antibacterial activity against some species of human pathogens that infect urinary tract and cause complicated infection while no anticandida activities was recorded. The tested Gram-positive pathogens were Aerococcus urinae, Enterococcus faecalis, Staphylococcus saprophyticus, and Streptococcus agalactiae. The highest bacterial growth inhibition was by Streptomyces lavendulocolor NB11 and against A. urinae while the highest inhibition of biofilm formation, exopolysaccharide (EPS) formation and α amylase production were recorded against St. agalactiae. The MIC ranged from 50-75 μg/ml) and no toxicity was recorded against Artimia salina as test organisms or antitumor activity against MCF-7 cell line (LD50 more than ≥0.6 mg/ml), while excellent antioxidant activity was recorded using DPPH (2, 2-diphenyl-1-picrylhydrazyl) compared to synthetic antioxidant Butylated Hydroxytoluene (BHT). Actinomycetes associated with marine algae showed excellent antibacterial and antioxidant activities which make them active candidates to be used in different biotechnological applications.