Study of bioremediation processes in soils contaminated with heavy metals and polycyclic aromatic hydrocarbons (PAH)

BARRIOS M; FESTA S; PEREZ-DONOSO JM; MORELLI IS; COPPOTELLI BM

Mar del Plata

Congreso; VIII Congreso Argentino de Microbiología General Samige; 2012

Sociedad Argentina de Microbiología General

During recent years there has been a un-restraint disposition of industrial residues, between them hydrocarbons and heavy metals are the more toxic and problematic components as they accumulate in water, soil, sediment and living organisms. Bioremediation is one of the methods of treatment applicable to contaminated soils widely accepted, especially for the lower cost and with fewer later consequences. This work aimed at studying the impact of the contamination with Phenanthrene (Phe) and the heavy metal Te (as K2TeO3) on soil microbial community. The bioremediation process was monitored in microcosms artificially contaminated with Phenanthrene (F), TeO3-2 (T) and Phenanthrene + TeO3-2 (F+T), during 60 days. On them were examined: (1) the degradation of phenanthrene (HPLC-UV); (2) the dynamics of the soil microbial community at level of cultivable bacteria: counts of heterotrophic populations, resistant populations and PAH degraders (MPN); and using culture-independent approaches: soil dehydrogenase activity and PCR-DGGE. The presence of genes codifying for dioxygenase enzyme (PCR) and the construction of a mini 16S rDNA-library were also performed. After 60 days of incubation, the percentage of Phe elimination was significantly higher in F+T microcosms (93.6 ±16.8%) than in F microcosms (81.8 ±9.5). TeO3-2 contamination provoked an increase in density of heterotrophic and TeO3-2 resistant bacteria. It was observed an increase in the PAH-degrading bacteria in F and F+T microcosms, although the presence of Te delayed that increase. Clear differences were observed in band profiles of DGGE along the bioremediation treatment, the contaminants caused a decrease in diversity in respect to control microcosm. The UPGMA analysis of the gel showed that independently of the treatment time, the DGGE profiles of T and F+T microcosms formed a marked cluster with a similitude higher than 60%. In another cluster (with less than 50% of similitude) were situated the DGGE profiles of F microcosm. This behavior showed that Te is modulating the response of microbial community to Phe. The diversity of the community was also studied through the construction of a mini 16S rDNA-Library during the period of higher metabolic activity of microcosms. A predominance of clones belonged to Xanthomonadals, which were previously found in soils contaminated with hydrocarbons and had been considered as indicators of contamination with heavy metals were found. Genes codifying for dioxygenase enzyme were evidenced in F microcosms. It was demonstrated that : presence of Te as a co-contaminant of Phe significantly favors its degradation during the experiment, and this favoring it is possible that due to stimulation of microorganisms by partial oxidation of Phe or soil organic matter; the presence of Te modulate the response of microbial community in the contaminated soil.