DDT in sediments from the northwest coast of Baja California (Mexico) and its biotransformation by Vibrio sp.

During December 2003, sediment samples were collected at 20 stations along file northwest coast of Baja California (Mexico). Analyses of DDT were performed by gas chromatography, percentage of particles <63 mu m in diameter, organic carbon. and sulphate-reducing bacteria. A bacterium from station 49, which showed the highest concentration of DDT and its metabolites DDE and DDD, was isolated and identified biochemically and molecularly to belong to the genus Vibrio. In the laboratory this bacterium was tested in minimal salts medium plus DDT and incubated at 28 degrees C under aerobic and anaerobic conditions for 90 days. In general, the sediments showed low concentrations of DDT, ranging from undetected to 4.78 ng g(-1), and the hi-hest concentrations occurred at the deepest stations containing higher percentages of particles <63 mu m and organic carbon concentrations. The isolated Vibrio strain showed an ability to biotransform DDT under aerobic and anaerobic conditions, presenting the o,p'-DDE and o,p'-DDD metabolites after 60 and 90 days of incubation in both conditions.