In this class, there are numerous genera of obligate and generalist hydrocarbonclastic bacteria. The obligate hydrocarbonoclastic bacteria (OHCB) share the ability to utilize hydrocarbons almost exclusively as a carbon source and until now they have been found only in the marine environment. The genera carrying out this metabolism are Alcanivorax, Oleiphilus, Oleispira, Thalassolitus, Cycloclasticus and Neptunomonas. Subsequently, additional species such as "Polycyclovorans", "Algiphilus" of the order Xanthomonadales and "Porticoccus hydrocarbonoclasticus" of the order Cellvibrionales that were isolated from phytoplankton. Groups of aerobic “generalist” hydrocarbon degraders can utilize hydrocarbons and nonhydrocarbon substrates as source of carbon and energy and are members within the genera Acinetobacter, Colwellia, Glaciecola, Halomonas, Marinobacter, Marinomonas, Methylomonas, Pseudoalteromonas, Pseudomonas, Rhodanobacter, Shewanella, Stenotrophomonas, and Vibrio.