摘要:

Four Mannich bases of some conjugated styryl ketones IIa-IId were examined for antifungal activity. These compounds were designed as thiol-alkylators and had two centers for attack by cellular thiols. The most potent compounds IIa and IIb possessed hydrophobic, electron-attracting substituents in the aryl rings and in general had minimum inhibitory concentration (MIC) values of 0.2-25 &mgr;M against a variety of fungi. None of the four compounds inhibited the growth of a number of bacteria (MIC > 100 &mgr;M). The minimum fungicidal concentration (MFC) values for IIa and IIb were generally either similar or twofold higher than the MIC figures for fungi. Compound IIa demonstrated rapid, concentration-dependent inhibition of the growth ofCandida albicansB311. The toxicity of IIa to normal human cells was much lower than the concentrations of this compound required to inhibit fungal growth. In summary, this study of four prototypic molecules has revealed that this class of compounds may have potential for further development as candidate antifungal agents.Key words: antifungal, styryl ketones,Candida albicans,Aspergillus fumigatus, susceptibility test.

ISSN:0008-4166    

DOI:10.1139/w97-127

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The production of toxic ergopeptine alkaloids by the fungiClaviceps purpureaandNeotyphodium coenophialuminvolves the activity of one or more nonribosomal peptide synthetases.Claviceps purpureaandN. coenophialumeach have several different peptide synthetase genes, fragments of which have been cloned previously. An additionalClaviceps purpureapeptide synthetase gene was cloned by hybridization with one of theN. coenophialumpeptide synthetase gene fragments. We detected the presence of mRNA from the peptide synthetase genes in cultures of different ages grown under conditions favorable or unfavorable for ergopeptine production. All four peptide synthetase genes fromClaviceps purpureawere transcribed under at least some of the experimental conditions. Transcripts from three of the four genes were detected under conditions consistent with their potential involvement in ergopeptine biosynthesis. All three peptide synthetase genes previously identified inN. coenophialumwere transcribed during symbiotic growth of this fungus with tall fescue, as well as in ergopeptine-producing cultures. The data show that all of the peptide synthetase genes are transcribed, that one of the peptide synthetase genes is dissociated from ergopeptine biosynthesis, and, as a result, prioritize the remaining genes for functional analyses by transformation-mediated gene disruption.Key words:Claviceps purpurea, endophyte, ergot, ergotamine,Neotyphodium coenophialum.

ISSN:0008-4166    

DOI:10.1139/w97-130

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The catalase-negative microaerophileSpirillum volutansis killed rapidly by levels of H2O2greater than 10 &mgr;M. A mutant isolated by single step mutagenesis with diethyl sulfate was able to survive and grow after exposure to 40 &mgr;M H2O2and was effective in eliminating H2O2added to the medium. Nevertheless, the mutant was no more colerant to O2than the wild type. The only apparent phenotypic difference between the wild type and the mutant was that the mutant had high NADH peroxidase activity (0.072 IU.mg-1) whereas the wild type had no detectable activity (<0.0002 IU.mg-1). NADH peroxidase has not previously been reported in gram-negative bacteria or in bacteria having a strictly respiratory type of metabolism.Key words: microaerophile,Spirillum volutans, peroxidase, oxygen tolerance, hydrogen peroxide.

ISSN:0008-4166    

DOI:10.1139/w97-122

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The putative 4.5S RNA ofHaemophilus influenzaewas identified in the genome by computer analysis, amplified by the polymerase chain reaction, and cloned. We have determined that this putative 4.5S RNA will complement anEscherichia colistrain conditionally defective in 4.5S RNA production. The predicted secondary structures of the molecules were quite similar, but Northern analysis showed that theH. influenzaeRNA was slightly larger than theE. coliRNA. TheH. influenzaegene encoding this RNA is the functional homolog of theffsgene inE. coli.Key words:ffsgene, complementation studies, small RNA, prokaryotic genetics.

ISSN:0008-4166    

DOI:10.1139/w97-124

出版商:NRC Research Press    

年代:1998

数据来源: NRC