Porticoccus hydrocarbonoclasticus sp. nov., an aromatic hydrocarbon-degrading bacterium identified in laboratory cultures of marine phytoplankton
Gutierrez, T and Nichols, PD and Whitman, WB and Aitken, MD, Porticoccus hydrocarbonoclasticus sp. nov., an aromatic hydrocarbon-degrading bacterium identified in laboratory cultures of marine phytoplankton, Applied and Environmental Microbiology, 78, (3) pp. 628-637. ISSN 0099-2240 (2012) [Refereed Article]
A marine bacterium, designated strain MCTG13d, was isolated from a laboratory culture of the dinoflagellate Lingulodinium polyedrum CCAP1121/2 by enrichment with polycyclic aromatic hydrocarbons (PAHs) as the sole carbon source. Based on 16S rRNA gene sequence
comparisons, the strain was most closely related to Porticoccus litoralis IMCC2115T (96.5%) and to members of the genera Microbulbifer (91.4 to 93.7%) and Marinimicrobium (90.4 to 92.0%). Phylogenetic trees showed that the strain clustered in a distinct phyletic line in the class Gammaproteobacteria for which P. litoralis is presently the sole cultured representative. The strain was strictly aerobic, rod shaped, Gram negative, and halophilic.
Notably, it was able to utilize hydrocarbons as sole sources of carbon and energy, whereas sugars did not serve as growth
substrates. The predominant isoprenoid quinone of strain MCTG13d was Q-8, and the dominant fatty acids were C16:1ω7c, C18:1ω7c, and C16:0. DNA G+C content for the isolate was 54.9 ± 0.42 mol%. Quantitative PCR primers targeting the 16S rRNA gene of this strain
showed that this organism was common in other laboratory cultures of marine phytoplankton. On the basis of phenotypic and
genotypic characteristics, strain MCTG13d represents a novel species of Porticoccus, for which the name Porticoccus hydrocarbonoclasticus sp. nov. is proposed. The discovery of this highly specialized hydrocarbon-degrading bacterium living in association with
marine phytoplankton suggests that phytoplankton represent a previously unrecognized biotope of novel bacterial taxa that
degrade hydrocarbons in the ocean.