Furthermore, the antibiotic PR9 showed the same MG132 molecular weight as PR10 (m/z 282) with the same molecular formula C12H14N2O2S2, suggesting isomeric compounds. The new dithiolopyrrolones (PR2, PR8, PR9 and PR10) were named, respectively, crotonyl-pyrrothine, sorbyl-pyrrothine, 2-hexonyl-pyrrothine and 2-methyl-3-pentenyl-pyrrothine. Our results showed that the antibacterial and antifungal activities of the newly obtained dithiolopyrrolones are related to their variable acyl groups. The antibiotic PR8 (sorbyl-pyrrothine) showed higher activity than other compounds against Gram-positive bacteria. The new

dithiolopyrrolone antibiotics showed a moderate activity against all fungi and yeasts tested (except for PR2 and PR9, which are not active against A. carbonarius, SB203580 solubility dmso F. oxysporum f. sp. lini, F. graminearum or F. moniliforme). Interestingly,

the antibiotic 2-methyl-3-pentenyl-pyrrothine (PR10) showed higher activity against A. carbonarius and Candida albicans, than showed by any of the other dithiolopyrrolones produced by S. algeriensis. In fact, the biological activity of dithiolopyrrolones is strongly influenced by the nature of variable acyl groups, as reported previously (Oliva et al., 2001; Li et al., 2007; Guo et al., 2008). Furthermore, none of the newly obtained antibiotics showed any activity against Gram-negative bacteria; similar results have been obtained with other dithiolopyrrolones produced by S. algeriensis (Lamari et al., 2002a; Merrouche et al., 2010). “
“Seven plasmid-mediated 16S rRNA methyltransferases (MTases), RmtA, RmtB, RmtC,

RmtD, RmtE, ArmA, and NpmA, conferring aminoglycoside resistance have so far been found in Gram-negative pathogenic microorganisms. In the present study, by performing an RNase protection assay, primer extension, and HPLC, we confirmed that RmtC indeed methylates at the N7 position of nucleotide G1405 in 16S rRNA as found in ArmA and RmtB. RmtC has an MTase activity specific for the bacterial 30S ribosomal subunit consisting of 16S rRNA and several ribosomal proteins, but not for the naked 16S rRNA, as seen in ArmA, RmtB, and NpmA. All seven 16S rRNA MTases have been found exclusively Megestrol Acetate in Gram-negative bacilli to date, and no plasmid-mediated 16S rRNA MTase has been reported in Gram-positive pathogenic microorganisms. Thus, we checked whether or not the RmtC could function in Gram-positive bacilli, and found that RmtC could indeed confer high-level resistance to gentamicin and kanamycin in Bacillus subtilis and Staphylococcus aureus. 16S rRNA MTases seemed to be functional to some extent in any bacterial species, regardless of the provenance of the 16S rRNA MTase gene responsible for aminoglycoside resistance.