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We used the concept of chemical space to explore a virtual library of bicyclic peptides formed by double thioether cyclization of a precursor linear peptide, and identified an antimicrobial bicyclic peptide (AMBP) with remarkable activity against several MDR strains of Acinetobacter baumannii and Pseudomonas aeruginosa.

In Bacillus subtilis the citM gene encodes the Mg 2+ -citrate transporter. A target site for carbon catabolite repression ( cre site) is located upstream of citM . Fusions of the citM promoter region, including the cre sequence, to the β-galactosidase reporter gene were constructed and integrated into the amyE site of B. subtilis to study catabolic effects on citM expression. In parallel with β-galactosidase activity, the uptake of Ni 2+ -citrate in whole cells was measured to correlate citM promoter activity with the enzymatic activity of the CitM protein. In minimal media, CitM was only expressed when citrate was present. The presence of glucose in the medium completely repressed citM expression; repression was also observed in media containing glycerol, inositol, or succinate-glutamate. Studies with B. subtilis mutants defective in the catabolite repression components HPr, Crh, and CcpA showed that the repression exerted by all these medium components was mediated via the carbon catabolite repression system. During growth on inositol and succinate, the presence of glutamate strongly potentiated the repression of citM expression by glucose. A reasonable correlation between citM promoter activity and CitM transport activity was observed in this study, indicating that the Mg 2+ -citrate uptake activity of B. subtilis is mainly regulated at the transcriptional level.

The dichloromethane extract of the leaves of Myrica serrata inhibits growth of Cladosporium cucumerinum, Bacillus subtilis, and Escherichia coli on TLC plates. Activity-guided fractionation led the isolation of 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (1), 2',4'-dihydroxy-6'-methoxy-5'-methylchalcone (aurentiacin A) (2), 2',6'-dihydroxy-4'-methoxy-3',5'-dimethyldihydrochalcone (3), 2'-hydroxy-4',6'-dimethoxy-3'-methyldihydrochalcone (4), and 2', 6'-dihydroxy-4'-methoxy-3'-methyldihydrochalcone (5). In addition, the flavanones demethoxymatteucinol (6) and cryptostrobin (7) were also identified.

The EtOAc soluble constituents of the unripe fruits of Ginkgo biloba showed motility inhibition followed by lysis of zoospores of the phytopathogenic Aphanomyces cochlioides. We purified 22:1-ω7-anacardic acid (1), 24:1-ω9-anacardic acid (2) and 22:0-anacardic acid (3), together with other related compounds, 21:1-ω7-cardol (4) and 21:1-ω7-cardanol (5) from the crude extracts of Ginkgo fruits. Amongst them, compound 1 was a major active agent in quality and quantity, and showed potent motility inhibition (98% in 30 min) followed by lysis (55% in 3 h) of the zoospores at 1 × 10−7 m. The 2-O-methyl derivative (1−c) of 1 displayed antibacterial activity against Bacillus subtilis, but practically inactive to Escherichia coli. A brief study on structure-activity relationships revealed that a carboxyl group on the aromatic ring and an unsaturated side chain in the anacardic acid derivative are important for strong motility inhibitory and lytic activities against the zoospore