Isolation and difference in anti-Staphylococcus aureus bioactivity of curvularin derivates from fungus Eupenicillium sp.

With the anti-microbial and anti-tumor composite screening model, bioassay-guided fractionation led to the isolation of two structurally related bioactive compounds, curvularin and alphabeta-dehydrocurvularin, from ethyl acetate extract of Eupenicillium sp. associated with marine sponge Axinella sp. Further study on the structure-activity relationship demonstrated that both compounds exhibited differences in bioactive profiles which are highly associated with their minor structural differences. Both curvularin and alphabeta-dehydrocurvularin have similar level of anti-fungal and anti-tumorous activity, while alphabeta-dehydrocurvularin is active against Staphylococcus aureus with a minimal inhibitory concentration of 375 microg/ml but curvularin does not. No detectable activity against Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa exists for both compounds. It is suggested that the partial planar backbone structure, due to the conjugation of pi electrons in the presence of a 3,4-double bond and the carbonyl group at position C-2 in alphabeta-dehydrocurvularin, acts as a key factor for the inhibition of S. aureus, a Gram-positive low G + C bacteria that are often the hospital-acquired and/or community-acquired pathogen.

[Marine microbial metagenomics: progress and prospect].

Preliminary statistics showed that there are more than one million species of microbes in marine environments that formed a dynamic genetic reservoir, among which the majority are not revealed and categorized due to barrier in cultivation techniques. However, the situation has changed in recent years because of the rapid development of phylogenetic studies based on small ribosomal RNA and rDNA sequencing independent to standard laboratory cultivation. These changes have significantly altered our understanding about microbial diversity and microbial ecology. In this review, we highlight some of recent progress and innovation in research on microbial diversity, and propose a metagenomic scheme as an alternative to overcome some of the barriers that still remain for exploitation of marine microbial diversity for its enormous potential in pharmaceutical applications. We believe that rapid progress in marine metagenomics allows direct access to the genomes of numerous non-cultivable microorganisms for their associated chemical prosperity.