| Abstract: |
Halomonas
species are recognized for producing exopolysaccharides (EPS) exhibiting amphiphilic properties that allow these macromolecules to interface with hydrophobic substrates, such as hydrocarbons. There remains a paucity of knowledge, however, on the potential of
Halomonas
EPS to influence the biodegradation of hydrocarbons. In this study, the well-characterized amphiphilic EPS produced by
Halomonas
species strain TG39 was shown to effectively increase the solubilization of aromatic hydrocarbons and enhance their biodegradation by an indigenous microbial community from oil-contaminated surface waters collected during the active phase of the Deepwater Horizon oil spill. Three
Halomonas
strains were isolated from the Deepwater Horizon site, all of which produced EPS with excellent emulsifying qualities and shared high (97-100%) 16S rRNA sequence identity with strain TG39 and other EPS-producing
Halomonas
strains. Analysis of pyrosequence data from surface water samples collected during the spill revealed several distinct
Halomonas
phylotypes, of which some shared a high sequence identity (≥97%) to strain TG39 and the Gulf spill isolates. Other bacterial groups comprising members with well-characterized EPS-producing qualities, such as
Alteromonas
,
Colwellia
and
Pseudoalteromonas
, were also found enriched in surface waters, suggesting that the total pool of EPS in the Gulf during the spill may have been supplemented by these organisms. Roller bottle incubations with one of the
Halomonas
isolates from the Deepwater Horizon spill site demonstrated its ability to effectively produce oil aggregates and emulsify the oil. The enrichment of EPS-producing bacteria during the spill coupled with their capacity to produce amphiphilic EPS is likely to have contributed to the ultimate removal of the oil and to the formation of oil aggregates, which were a dominant feature observed in contaminated surface waters. |
