comparative biochemical study on two marine endophytes, Bacterium SRCnm and Bacillus sp. JS, Isolated from red sea algae

Two marine endophytic bacteria were isolated from the Red Sea algae; a red alga; Acanthophora dendroides and the brown alga Sargassum sabrepandum. The isolates were identified based on their 16SrRNA sequences as Bacterium SRCnm and Bacillus sp. JS. The objective of this study was to investigate the potential anti-microbial and antioxidant activities of the extracts of the isolated bacteria grown in different nutrient conditions. Compared to amoxicillin [25micro g/disk] and erythromycin [15micro g/disk], the extracts of Bacterium SRCnm in media II, III, IV and V were potent inhibitors of the gram-positive bacterium Sarcina maxima even at low concentrations. Also, the multidrug resistant Staphylococcus aureus [MRSA] was more sensitive to the metabolites produced in medium [II] of the same endophyte than erythromycin [15micro g/disk]. A moderate activity of the Bacillus sp. JS extracts of media I and II was obtained against the same pathogen. The total compounds [500ug/ml] of both isolated endophytes showed moderate antioxidant activities [48.9% and 46.1%, respectively]. LC/MS analysis of the bacterial extracts was carried out to investigate the likely natural products produced. Cyclo[D-cis-Hyp-L-Leu], dihydrosphingosine and 2-Amino-1,3- hexadecanediol were identified in the fermentation medium of Bacterium SRCnm, whereas cyclo [D-Pro-L-Tyr] and cyclo [L-Leu-L-Pro] were the suggested compounds of Bacillus sp. JS

Imidazole alkaloids from the indopacific sponge Pericharax heteroraphis

Chemical investigation of the sponge Pericharax heteroraphis [Polejeff] collected in Indonesia, has led to the isolation of three imidazole alkaloids, preclathridine-A [1], leucettamine-B [2] and leucettamine-A [3]. The structures of the isolated compounds were unambiguously established by [1]D and [2]D NMR and mass data. This is the first report of this class of compounds from the P. heteroraphis sponge. Investigation of the antimicrobial activities of the isolated compounds showed that leucettamin-A [3] was active against the gram-positive bacteria Staphylococcus aureus and the fungus Cladosporium herbarum, while other compounds were inactive