Preliminary characterization of hydrocarbon degrading strains isolated from the Río de la Plata estuary: alkane hydroxylase gene analysis.

IZZO, SILVINA; LOZADA, MARIANA; DIONISI, HEBE; COSTAGLIOLA, M; PERESSUTTI, SILVIA

Mar del Plata

Congreso; VII Congreso de Microbiología General; 2012

Sociedad Argentina de Microbiología General

The Río de la Plata estuary, form one of the most important estuarine environments in the continent, being a highly productive area that sustains valuable artisanal and coastal fisheries. However, this zone is exposed to chronic pollution of hydrocarbons, mainly associated with chemical industry, oil refining and port activities. These pollutants not only are toxic to fishes and other aquatic organisms but also have been found to bioaccumulate in marine organisms with possible transfer to humans via sea-food.In this study, we isolated hydrocarbon-degrading bacteria from water samples collected along this marine-estuarine system, and tested for the presence of genes associated with hydrocarbon biodegradation. We isolated 24 strains by enrichment on salt mineral medium and gas-oil, phenanthrene or anthracene as carbon and energy sources. Physiological and biochemical tests were performed in order to characterize these strains. All the strains were preliminary characterized as Gram negative, oxidase- and catalase-positive bacteria. In addition, diverse carbon sources were tested as substrates for growth, including gasoil, phenanthrene, anthracene, pentadecane, hexadecane and phenyldecane. 90% of the tested strains were capable of growing on pentadecane and hexadecane, while 30% grew in anthracene, phenanthrene and phenyldecane, indicating the degradative potential of these strains. Restriction Fragment Length Polymorphism (RFLP) analysis of 16S rRNA genes amplified from these strains resulted in 6 unique RFLP patterns, suggesting some level of diversity in the microorganisms that were able to grow in the chosen conditions. These isolates are being identified by sequencing the 16S rRNA genes and subsequent phylogenetic analysis.The isolates were screened for the presence of alkB genes, which encode alkane hydroxylase enzymes that initiate biodegradation by introducing oxygen into the substrate. This gene is often used as functional biomarker for the characterization of aerobic alkane biodegradation. We amplified alkB gene fragments by polymerase chain reaction (PCR) method, using a degenerate primer set (AlkB484F-AlkB824R). Most alkane degrading bacterial isolates exhibited the presence of alkB genes which will be sequenced and analyzed phylogenetically.The present work is the first report about characterization of hydrocarbon degrading bacteria carrying catabolic genes in this contaminated area. Further studies are being carried out on these strains in order to screen genes encoding for the catalytic alpha subunit of aromatic ring-hydroxylating dioxygenases.