Petroleum-influenced beach sediments of the Campeche Bank, Mexico: diversity and bacterial community structure assessment.

The bacterial diversity and community structure were surveyed in intertidal petroleum-influenced sediments of ≈ 100 km of a beach, in the southern Gulf of Mexico. The beach was divided in twenty sampling sites according to high, moderate and low petroleum influence. Densities of cultured heterotrophic (HAB) and hydrocarbon degrading bacteria (HDB) were highly variable in sediments, with little morphological assortment in colonies. PCR-RISA banding patterns differentiated distinct communities along the beach, and the bacterial diversity changed inversely to the degree of petroleum hydrocarbon influence: the higher TPH concentration, the lower genotype diversity. Seven DNA sequences (Genbank EF191394 -EF191396 and EF191398 -EF191401) were affiliated to uncultured members of Gemmatimonas, Acidobacterium, Desulfobacteraceae, Rubrobacterales, Actinobacterium and the Fibrobacteres/Acidobacteria group; all the above taxa are known for having members with active roles in biogeochemical transformations. The remaining sequences (EF191388 - EF191393 and EF191397) affiliated to Pseudoalteromonas, and to oil-degrading genera such as Pseudomonas, Vibrio and Marinobacter, being the last one an obligate oil-degrading bacterium. An exchange of bacteria between the beach and the oil seep environment, and the potential cleaning-up role of bacteria at the southern Gulf of Mexico are discussed.