Incursion in the study of functional interactions between bacterial strains from a phenanthrene-degrading consortium

S. FESTA; B.M. COPPOTELLI; I .S. MORELLI

San Miguel de Tucumán

Congreso; VII Congreso Argentino de Microbiología General Samige del Bicentenario; 2011

SAMIGE

In bioremediation of aged contaminated soils, the applications of bioaugmentation with bacterial consortia is of special concern since syntrophic interactions are an extremely interesting example of “fitness support”, specially in the biodegradation of aromatic compounds where the biochemical steps are shared among community members in order to completely mineralize recalcitrant and/or toxic substrates. In a previous work a phenanthrene degrading consortium was obtained from an aged contaminated soil and characterized in terms of structure, diversity and functionally, finding that it shows an effective phenanthrene degradation (59%) with the concomitant accumulation of 1-hydroxy 2-naphtoic acid. Four strains were isolated and identified by PCR-sequencing as Sphingobium sp. (AM), two Pseudomonas sp. (Bc y T) and one Enterobacter sp. (B1). In the present work some physiological properties of the isolates, related with the phenanthrene degradation, were investigated with the aim of revealing bacterial interactions that take place in the consortium during degradation of the contaminant. Also a metaproteomic approach was performed with the objective of studying the functional dynamics of the consortium. The four isolates showed growth in LMM with 200 mg/l of phenanthrene as sole carbon and energy source, although only AM strain was confirmed to be a phenanthrene degrader, showing a percentage of degradation of 55 %, after 48 h of incubation, with the concomitant accumulation of 1-hydroxy 2-naphtoic acid (74.47 ± 7.5 mg/l). This is consistent with a previous result that showed that AM was the predominant strain at the beginning of the phenanthrene degradation by de consortium. When the four strains were cultivated in 1-hydroxy 2-naphtoic acid as sole carbon an energy source only the T and Bc isolates showed significant increase in cellular density but none showed 1-hydroxy 2-naphtoic acid degradation after 96h of incubation. In addition, combinations of the strains in pairs (AM+Bc, AM+B1 y AM+T) were cultivated in MML with phenanthrene in order to study bacterial cooperation and degradation capacities. In the tree combinations, all the strains showed an increase in cellular density, and the phenanthrene degradation was higher than 80 %. The metaproteomic study by 2DE of the consortium during phenanthrene degradation was performed at days 4 and 15 of incubation. A significant higher diversity was observed in protein expression after 15 days of incubation, this could be correlated with previous findings where, a significant degradation of phenanthrene occurred between the first 7 days of incubation, after what no degradation was observed. These results could be indicating that whereas in the first days of incubation the consortium metaproteome is dominated by the specific phenanthrene degradation enzymes, after 15 days the metaproteome would reveal the diversity of phenanthrene by-products available as carbon source.