| The three phthalate isomers are widely found in the environment due to their extensive use in the manufacture of plastics. Many microorganisms have been isolated for their ability to degrade phthalate isomers. In this study, we focused on nine different phthalate degrading bacterial strains (YZW-A, -B, -C, -D, -E, -F, -G, -H, and -I) which were isolated from Passaic River sediment and belong to different genera (Comamonas, Pseudomonas, Acinetobacter , and Arthrobacter).;Our work aims to identify the presence and divergence of the phthalate, isophthalate and terephthalate degradative genes in the nine strains isolated from the same sediment sample. The oph, iph, and/or tph genes in Comamonas testosteroni strains (YZW-B, -E, and -F) and Pseudomonas strains (YZW-A and -G) were determined by PCR and inverse PCR. Sequence analyses indicate that phthalate, isophthalate and terephthalate degrading bacterial isolates at the same location are not simply clones of each other and that the genes identified are linked specifically to these bacterial strains.;In order to investigate whether each phthalate isomer would specifically induce the corresponding degradative gene cluster and how regulatory genes control phthalate isomers degradation, we used quantitative real time PCR to measure the expression of genes encoding phthalate (ophA2), isophthalate (iphA2), terephthalate (tphA2) dioxygenase in YZW-B. qPCR data showed that the ophA2, iphA2, and tphA2 genes were specifically induced by phthalate, isophthalate, and terephthalate, respectively. The tphA2 gene was slightly upregulated by isophthalate. Furthermore, we knocked out phthalate regulatory gene ophR and isophthalate regulatory gene iphR in YZW-B and analyzed the ophA2, iphA2, and tphA2 gene expression patterns in the ophR or iphR knock out mutant using qPCR. Gene knockout and qPCR showed that the ophR gene and the iphR gene encoded repressors that negatively controlled the phthalate and the isophthalate gene expression, respectively. |
