Effect of phenolic compounds and osmotic stress on the expression of penicillin biosynthetic genes from Penicillium chrysogenum var. halophenolicum strain
AbstractPhenol and phenolic compounds are aromatic pollutants that inhibit biological treatment of wastewaters. Penicillium chrysogenum var. halophenolicum is a halotolerant fungus that previously showed the ability to degrade phenol and resorcinol in high salinity conditions. The presence of the penicillin biosynthetic cluster in P. chrysogenum var. halophenolicum was recently described. In this article, we examined the expression of pcbAB, pcbC and penDE, genes responsible for δ-(L-α-aminoadipyl)-L-cysteinyl-D-valine synthetase, isopenicillin N synthase and isopenicillin N acyltransferase activities, respectively, in P. chrysogenum var. halophenolicum. A quantitative PCR (qPCR) approach was used to determine how these genes were expressed in media with 2% and 5.9% NaCl supplemented with phenol, catechol, hydroquinone and resorcinol as the sole carbon source. The effect of salt on the capability of P. chrysogenum var. halophenolicum to degrade aromatic compounds was measured using HPLC. qPCR analysis of RNA extracted from P. chrysogenum var. halophenolicum indicated that the expression levels of pcbAB, pcbC and penDE decreased in high saline concentrations compared to the levels expressed in media with glucose. High concentrations of salt significantly repress the expression of pcbAB and penDE. The pcbC gene was expressed differentially in catechol containing medium. There was no evident relationship between the expression levels of penicillin biosynthetic genes and yields of penicillin. Meanwhile, the presence of phenol and phenolic compounds seems to positively influence the antibiotic production; high concentrations of salt stimulated penicillin production. These results support the hypothesis that phenol, phenolic compounds and high concentrations of salt could act like a stress factor for P. chrysogenum var. halophenolicum resulting in higher yields of β-lactam antibiotic production.
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