Background
Antibiotic resistance is a growing problem that can be ameliorated by the discovery of novel drug candidates. Bacterial associates are often the source of pharmaceutically active natural products isolated from marine invertebrates, and thus, important targets for drug discovery. While the microbiomes of many marine organisms have been extensively studied, microbial communities from chemically-rich nudibranchs, marine invertebrates that often possess chemical defences, are relatively unknown.
Methods
We applied both culture-dependent and independent approaches to better understand the biochemical potential of microbial communities associated with nudibranchs. Gram-positive microorganisms isolated from nudibranchs collected in the Red Sea were screened for antibacterial and antitumor activity. To assess their biochemical potential, the isolates were screened for the presence of natural product biosynthetic gene clusters, including polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) genes, using PCR. The microbiomes of the nudibranchs were investigated by high-throughput sequencing of 16S rRNA amplicons.
Results
In screens against five model microorganisms, 51% of extracts displayed antimicrobial activity against more than one organism, and 19% exhibited antitumor activity against Ehrlich’s ascites carcinoma. Sixty-four percent of isolates contained PKS and NRPS genes, suggesting their genomes contain gene clusters for natural product biosynthesis. Thirty-five percent were positive for more than one class of biosynthetic gene. These strains were identified as belonging to the Firmicutes and Actinobacteria phyla via 16S rRNA gene sequencing. In addition, 16S rRNA community amplicon sequencing revealed all bacterial isolates were present in the uncultured host-associated microbiome, although they were a very small percentage of the total community. Taken together, these results indicate that bacteria associated with marine nudibranchs are potentially a rich source of bioactive compounds and natural product biosynthetic genes.
is capable of producing approximately 106kg of sugar and 46kg of molasses. A typical molasses to ethanol conversion rate is 4kg of molasses/L ethanol (Lavarack, 2001). However, this rate can vary based on production practices and sugar content of the molasses (Nguyen et al., 2009 andSilalertruksa &Gheewala, 2010).Molasses composition is usually influenced by the variety and maturity of the cane and beet, soil, climate and the processing conditions in the factory (El-Gendy et al., 2013). High yielding and efficient fermentation of molasses with varying composition requires selection of special yeast strains having high tolerances to inhibitory conditions as well as ability of fast fermentation. Other natural requirements like tolerance to high alcohol, sugar and temperature are also necessary (Bazmi et al., 2007
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