Expression of the PAHs biodegradative genes in microorganisms isolated from contaminated sites in Patagonia Argentina

ISAAC P; ESTEVEZ MC; FERRERO MA

Rosario

Congreso; IX Congreso Argentino de Microbiologia General -SAMIGE; 2013

SAMIGE

Polycyclic Aromatic Hydrocarbons (PAHs) are organic compounds with toxic, mutagenic and carcinogenic properties. Many bacteria have shown to mineralize PAHs and seem to play an important role in removal of contaminants from the environments. Successful bioremediation depends on achieving high rates of microbial activity. There are numerous environmental factors that can activate or repress gene expression and thereby modulate microbial activity. Study of gene expression may offer insights into how specific catabolic genes are regulated. In this study, a combinated gen probe-retrotranscription PCR assay was used to evaluate the regulation of the expression of the nahAc gene (naphthalene dioxygenase) in different growth conditions. PAHs potential degradation of three Pseudomonas strains isolated from contaminated Patagonian-sediments was estimated by hydrocarbon-loss. Naphthalene was almost completely removed (near to 100%) from all cultures after 25 h of incubation. P. monteilii P26 was capable of remove 90 % of phenanthrene, while P. xanthomarina N12 and P. stutzeri N3 degraded 41% and 55%, respectively after 30 h of incubation. No pyrene degradation was observed after 48 h at the same growth condition. Naphthalene dioxygenase (NDO) is an inducible multicomponent enzyme system which initiates the metabolism of naphthalene and other PAHs in bacteria (Fig.1). Expression of NDO was measured by both, Northern blot and semiquantitative RT-PCR of the nahAc gene, in the presence of naphthalene, phenanthrene or pyrene (Fig. 2). NDO expression was detected in P. monteilii P26, P. xanthomarina N12 and P. stutzeri N3 strains after naphthalene exposition. Phenanthrene was capable of induce nahAc transcription in P. monteilii P26 and P. xanthomarina N12, but not in P. stutzeri N3 strain. Interestingly, after pyrene exposition an intense band corresponding to nahAc transcription was detected only in cultures of P. stutzeri N3, even though pyrene was not degraded in these conditions (Fig. 3). These results suggest that induction of the nahAc gene and subsequent detection of the nahAc transcript depends of both, microorganism and growth conditions. The research demonstrates that the use of a gene expression assay to monitor the impact of substrate presence provides complementary information concerning the biodegradation process that must be confirmed by traditional biodegradation assays such as cell growth or substrate disappearance.