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.

[Construction of prokaryotic expression vector for MAP30 gene and study of PCR methods for rapid identification of recombinant].

Based on the sequence reported by Lee-Huang,S, we cloned the MAP30 gene of Momordica charantia (balsam pear) into a prokaryotic expression vector pET28a (+). A method by using PCR for rapid identification of positive clone was developed. Result showed this screening method can be used to detect positive colonies from samples of bacterial, purified plasmid, liquid culture,and liquid culture treated with mixture of phenol/Chloroform. The result from liquid-culture-treated- PCR (LCT-PCR) is very close to that of by plasmid-PCR. LCT-PCR is reliable and much easier to used than plasmid-PCR, therefore the LCT-PCR can be used for clone screening during the molecular cloning.