Marine, Aerobic Hydrocarbon-Degrading Gammaproteobacteria: Overview

The class Gammaproteobacteria contains the most important genera and largest diversity of obligate and generalist hydrocarbonoclastic bacteria that are found in the marine environment. With the exception of Planomicrobium alkanoclasticum (a Gram-positive of the Firmicutes), all obligate hydrocarbonoclastic bacteria (OHCB), represented by the genera Alcanivorax, Cycloclasticus, Neptunomonas, Oleibacter, Oleiphilus, Oleispira, and Thalassolituus, are represented within the Gammaproteobacteria. Notably, the OHCB appear to be confined to marine environments where they were initially discovered – alluding to an evolutionary genesis in the ocean – and where they are commonly found to become strongly enriched at oil contaminated sites. Prospecting studies aimed in identifying new taxa of hydrocarbonoclastic bacteria from underexplored biotopes in the ocean have uncovered novel strains of OHCB and generalist hydrocarbon degraders within the Gammaproteobacteria, which has increased the known diversity of hydrocarbonoclastic bacteria that constitute this physiologically and phylogenetically diverse class.