Novel polycyclic aromatic hydrocarbon dioxygenase genes detected in coastal sediments of Patagonia.

LOZADA, M; RIVA MERCADAL JP; DI MARZIO, WD; FERRERO MA; DIONISI H

Buenos Aires

Congreso; IV Congreso Argentino de Microbiología General (SAMIGE); 2007

SAMIGE

The diversity of polycyclic aromatic hydrocarbon (PAH)-degrading bacteria present in the marine environment remains largely unknown, in particular in sub-Antartic regions. Genes encoding for the catalytic component (a subunit) of class III aromatic ring-hydroxylating dioxygenases (ARHDs) were used as functional targets to explore the diversity of these organisms in coastal marine sediments of Patagonia. Clone libraries of polymerase chain reaction (PCR)-amplified ARHD gene fragments were constructed from five intertidal sediment samples, screened by restriction fragment length polymorphism analysis and clones from each restriction pattern were selected for sequencing. Six different dioxygenase gene types were detected with the degenerate primer set Ac114f and Ac596r [Wilson et al. (1999) Appl. Environ. Microbiol. 65, 80-87]. Two of these clone types were closely related (>95% similarity at the nucleotide level) to previously described genes: (a) phnAc genes cloned from Burkholderia sp. Ch1-1, Ch3-5, Cs1-4 and Eh1-1 (AY367784-7) and Alcaligenes faecalis AFK2 (AB024945) and (b) archetypical nahAc-like genes (Pseudomonas type) . The other four gene types were only distantly related to already published class III ARHD gene sequences. Identities of their deduced amino acid sequences with previously identified ARHD genes ranged from 60 to 66%. Furthermore, all these clone types carry a bacterial ring-hydroxylating dioxygenases alpha-subunit signature, which suggest that the gene fragments cloned belong to novel types of dioxygenases. On the other hand, a second primer set identified gene fragments closely related to phnA1-like genes cloned from marine PAH-degraders belonging to the genera Cycloclasticus. These results represent the groundwork to try to understand the role of PAH-degrading microbial populations in the self-purifying capacity of coastal marine environments subjected to anthropogenic contamination.