RESUMO
Furfural is an inhibitory side product formed during the depolymerization of hemicellulose by mineral acids. Genomic libraries from three different bacteria (Bacillus subtilis YB886, Escherichia coli NC3, and Zymomonas mobilis CP4) were screened for genes that conferred furfural resistance on plates. Beneficial plasmids containing the thyA gene (coding for thymidylate synthase) were recovered from all three organisms. Expression of this key gene in the de novo pathway for dTMP biosynthesis improved furfural resistance on plates and during fermentation. A similar benefit was observed by supplementation with thymine, thymidine, or the combination of tetrahydrofolate and serine (precursors for 5,10-methylenetetrahydrofolate, the methyl donor for ThyA). Supplementation with deoxyuridine provided a small benefit, and deoxyribose was of no benefit for furfural tolerance. A combination of thymidine and plasmid expression of thyA was no more effective than either alone. Together, these results demonstrate that furfural tolerance is increased by approaches that increase the supply of pyrimidine deoxyribonucleotides. However, ThyA activity was not directly affected by the addition of furfural. Furfural has been previously shown to damage DNA in E. coli and to activate a cellular response to oxidative damage in yeast. The added burden of repairing furfural-damaged DNA in E. coli would be expected to increase the cellular requirement for dTMP. Increased expression of thyA (E. coli, B. subtilis, or Z. mobilis), supplementation of cultures with thymidine, and supplementation with precursors for 5,10-methylenetetrahydrofolate (methyl donor) are each proposed to increase furfural tolerance by increasing the availability of dTMP for DNA repair.
Assuntos
Farmacorresistência Bacteriana , Escherichia coli/efeitos dos fármacos , Escherichia coli/genética , Furaldeído/toxicidade , Expressão Gênica , Engenharia Metabólica , Timidilato Sintase/metabolismo , Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/genética , Escherichia coli/metabolismo , Etanol/metabolismo , Furaldeído/metabolismo , Redes e Vias Metabólicas/genética , Plasmídeos , Polissacarídeos/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Timidilato Sintase/genética , Zymomonas/efeitos dos fármacos , Zymomonas/genéticaRESUMO
The total extract and fractions with different solvents, obtained from leaves of Tagetes minuta, showed several degrees of antimicrobial activity against Gram positive and Gram negative microorganisms. The same fractions were inactive against Lactobacillus, Zymomonas and Saccharomices species. The major component of the extract: quercetagetin-7-arabinosyl-galactoside, showed significant antimicrobial activity on pathogen microorganisms tested. Correlation results were carried out using chloramphenicol as standard antibiotic.