Five New Amicoumacins Isolated from a Marine-Derived Bacterium Bacillus subtilis

Four novel amicoumacins, namely lipoamicoumacins A–D (1–4), and one new bacilosarcin analog (5) were isolated from culture broth of a marine-derived bacterium Bacillus subtilis, together with six known amicoumacins. Their structures were elucidated on the basis of extensive spectroscopic (2D NNR, IR, CD and MS) analysis and in comparison with data in literature

Novel bacteria from the Red Sea

The marine environment contains a huge diversity of bacteria and may comprise of over a million different species. Analysis of cultured bacteria usually provides vast amount of information including phylogenetic relationship, ecological roles, metabolic pathway as well as production mechanism of bioactive compound. However, up to now, only a few thousands of bacterial species have been properly cultured and characterized. Therefore, the biodiversity of marine microbes along with the versatility of their bioactive metabolites is substantially underexplored. Consequently, it is highly motivated to expand culture collection and thus our knowledge of marine bacteria. With the precious opportunity of having direct access to environmental samples including water, brine, sediment and marine invertebrate tissues from a unique and less-explored environment, the Red Sea, my thesis work focused on discovering cultivate novel bacteria with modified cultivation techniques. After preliminary identification of novel candidates by 16S rRNA sequence analysis and phenotypic characteristics, a comprehensive polyphasic bacterial taxonomic characterization and description were performed to provide solid evident to support the establishment of new genus and species. This polyphasic approach employed a wide range of techniques to include all possible data in phenotypic, biochemical, genotypic, and phylogentic aspects. Therefore, it was chosen as the main research strategy in this MPhil thesis project. After preliminary analysis, I identified three novel bacterial species. They were then characterized in details and were proposed as two novel species, Erythrobacter pelagi, Marinobacter xestospongiae and one novel genus Profundibacterium mesophilum, respectively

Four New Antibacterial Xanthones from the Marine-Derived Actinomycetes Streptomyces caelestis

Four new polycyclic antibiotics, citreamicin θ A (1), citreamicin θ B (2), citreaglycon A (3), and dehydrocitreaglycon A (4), were isolated from marine-derived Streptomyces caelestis. The structures of these compounds were elucidated by 1D and 2D NMR spectra. All four compounds displayed antibacterial activity against Staphylococcus haemolyticus, Staphylococcus aureus, and Bacillus subtillis. Citreamicin θ A (1), citreamicin θ B (2) and citreaglycon A (3) also exhibited low MIC values of 0.25, 0.25, and 8.0 μg/mL, respectively, against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300