Study of the competence of a PAH-degrading strain to establish and promote the phenanthrene degradation by a native Phenanthrene-degrading consortium.

MACCHI MARIANELA; FESTA S; MORELLI I. S; COPPOTELLI, BM

Copenhague

Simposio; 14th International Symposium on Microbial Ecology-; 2012

International Society of Microbial Ecology

PAH are ubiquitous environmental pollutants, whose presence causes acute health hazard. It has been observed that bacteria are the most active agents of bioremediation, and in some cases, bioaugmentation is the best option to clean the polluted area. In order to increase the degrading potential of the microbial community, genome entered must participate in the central energy flux and competitiveness of the inoculated organism is intimately related to competition for resources with the native microbial populations in the contaminated site. So, it is critical to conduct studies to understand not only how the inoculum affects the microbial community structure (PCR-DGGE, genomic libraries, FISH, etc.), but also how bioaugmentation settles the microorganisms participating in the total energy flux. This work aimed at studying the competitiveness of a bacterial inoculant for establishing within a degrading indigenous community and to compare the behavior of an inoculated microbial consortium (I-CON) with the one of the non-inoculated consortium (CON) in phenanthrene cultures. A phenanthrene degrading consortium was obtained from an aged contaminated soil and characterized in terms of structure, diversity and functionally. Four strains (AM, Bc, T y B1) were isolated, characterized and identified by PCR-sequencing as Sphingobium sp, (AM), Pseudomonas sp. (Bc y T) and Enterobacter sp. (B1). The microbial consortium was inoculated with the strain Sphingomonas paucimobilis 20006FA, a phenanthrene-degrader previously isolated from a freshly contaminated soil and characterized in our laboratory, and a comparison of the behavior of a culture of I-CON in Liquid Mineral Medium (LMM) with phenanthrene as sole carbon and energy source, with the one of CON, was performed. On these cultures were examined: the degradation kinetics of phenanthrene and the appearance of 1-hydroxy-2-naphthoic acid (AHN) (intermediate metabolite of the phenanthrene degradation pathways) (HPLC) and the dynamics and structure of the bacterial consortium (count of heterotrophic populations on R2A and PAH degraders (MPN), Denaturant Gradient Gel Electrophoresis (PCR-DGGE) and Fluorescent in situ hybridization (FISH). The CON and I-CON consortia were cultivated in LMM with 200 mg/l of phenanthrene, showing a percentage of degradation of 59 % with the concomitant accumulation of 1-hydroxy 2-naphtoic acid (30 mg/L) and 78% without evidence of accumulation of 1-hydroxy 2-naphtoic acid respectively, after 15 days of incubation. Cultivable population dynamic showed significant differences in consortia composition between the two cultures, being the colonies with the macroscopic characteristic of the inoculated strain the predominant in I-CON cultures along the whole experiment. These differences were also evidenced when studying community structure by molecular tools (PCR-DGGE and FISH). In addition, both populations? studies demonstrated the permanence of the inoculated strain in the cultures. In conclusion, the comparison of the degradation capacity of CON and I-CON demonstrated that inoculation with S. paucimobilis 20006FA significantly enhanced phenanthrene removal, and that the inoculated strain was predominant until the end of the incubation time, confirming the establishment of syntrophic relations within the consortium.