Isolation of hydrocarbonoclastic denitrifying bacteria from berre microbial mats

Facultative anaerobic bacteria were isolated from the chronically polluted sediment from the Berre Lagoon after amendment with nitrate and octadecane or pristane. Seventy-one isolates were tested for their potential to utilize nitrate under anaerobic conditions and to degrade aerobically hydrocarbons using a new agar plate test. The electrophoretic mobility of each amplified 16S rDNA fragment was performed by DGGE and each isolate was affiliated to a phylotype. Most of the isolates were denitrifiers or at least nitrate reducers and some heterogeneity of nitrate utilization among a 16S rDNA phylotype was observed. The addition of hydrocarbons resulted in a drastic change in the structure of the isolated strains. Most hydrocarbon potential degraders were restricted to few 16S rDNA phylotypes that remained or appeared between the two steps of the isolation procedure.