120
Schedler et al. (2014) reported that pressure impacted the growth and alkanedegradation capability of Rhodococcus qingshengii TUHH-12 isolated from surface
seawater of the Norwegian Arctic. Growth during the exponential phase and the rate
of n-hexadecane degradation were approximately twofold higher at atmospheric
pressure (0.1 MPa) in comparison to pressures mimicking the deep sea (15 MPa).
No growth of aromatic hydrocarbon-degrading Sphingobium yanoikuyae B1, isolated from polluted stream, was observed when the strain was grown on naphthalene
at 13.9 MPa. Interestingly, naphthalene biodegradation capability was still observed
at a pressure of 13.9 MPa, albeit slower than at 0.1 MPa. The growth yield of
Alcanivorax dieselolei KS_293 and A. jadensis KS_339, both isolated from surface
seawater, on n-dodecane decreased with increasing hydrostatic pressure (5 and
10 MPa) (Scoma et al. 2016a), and 95% of expressed genes were downregulated,
especially genes related to translation (Scoma et al. 2016a). The authors posited that
pressure is the major constraint of Alcanivorax distribution in the deep sea (Scoma
et al. 2016b). In contrast, pressure did not impact growth rate or n-hexadecane biodegradation of Marinobacter hydrocarbonoclasticus, isolated from 3475 m bsl
Mediterranean seawater, when grown at 0.1 MPa and 35 MPa (Grossi et al. 2010).
Based on the available data, it is tempting to suggest that the investigated strains
of hydrocarbon-degrading bacteria are adapted to their in situ environment, and
therefore the origin of the culture determines pressure tolerance. However, as mentioned above, the field is in its infancy. Further investigations are warranted to
improve understanding of pressure effects on the physiology of deep sea
hydrocarbon- degrading microorganisms, and pressure should be considered as a
crucial factor in deep sea biodegradation studies.
7.5 Conclusions
The Deepwater Horizon (DWH) discharge is unique in that it occurred in the deep
sea, and unparalleled volumes of chemical dispersant were applied during emergency response efforts. A lack of knowledge on biodegradation in the deep sea hampered efforts to predict the fate and transport of released oil. Despite tremendous
progress, many knowledge gaps remain with regard to biodegradation under the
low-temperature and high-pressure conditions found in the deep ocean. Since biodegradation rates were not determined directly under in situ conditions, the role of
biodegradation as well as dispersant application on the fate and transport of petroleum hydrocarbons remains under debate. Hydrostatic pressure was shown to substantially impact biodegradation rates in both the water column and sediments of the
deep sea. However, as mentioned above, the field is in its infancy. Further investigations are warranted to improve understanding of pressure effects on the physiology
of deep sea hydrocarbon-degrading microorganisms, and pressure should be considered as a crucial factor in deep sea biodegradation studies. Direct rate measurements and determination of oceanographic controls such as pressure are sorely
needed to improve the effective parameterization of oil plume models. Ongoing
technological advances show potential to address these knowledge gaps.
J. E. Kostka et al.
Schedler et al. (2014) reported that pressure impacted the growth and alkanedegradation capability of Rhodococcus qingshengii TUHH-12 isolated from surface
seawater of the Norwegian Arctic. Growth during the exponential phase and the rate
of n-hexadecane degradation were approximately twofold higher at atmospheric
pressure (0.1 MPa) in comparison to pressures mimicking the deep sea (15 MPa).
No growth of aromatic hydrocarbon-degrading Sphingobium yanoikuyae B1, isolated from polluted stream, was observed when the strain was grown on naphthalene
at 13.9 MPa. Interestingly, naphthalene biodegradation capability was still observed
at a pressure of 13.9 MPa, albeit slower than at 0.1 MPa. The growth yield of
Alcanivorax dieselolei KS_293 and A. jadensis KS_339, both isolated from surface
seawater, on n-dodecane decreased with increasing hydrostatic pressure (5 and
10 MPa) (Scoma et al. 2016a), and 95% of expressed genes were downregulated,
especially genes related to translation (Scoma et al. 2016a). The authors posited that
pressure is the major constraint of Alcanivorax distribution in the deep sea (Scoma
et al. 2016b). In contrast, pressure did not impact growth rate or n-hexadecane biodegradation of Marinobacter hydrocarbonoclasticus, isolated from 3475 m bsl
Mediterranean seawater, when grown at 0.1 MPa and 35 MPa (Grossi et al. 2010).
Based on the available data, it is tempting to suggest that the investigated strains
of hydrocarbon-degrading bacteria are adapted to their in situ environment, and
therefore the origin of the culture determines pressure tolerance. However, as mentioned above, the field is in its infancy. Further investigations are warranted to
improve understanding of pressure effects on the physiology of deep sea
hydrocarbon- degrading microorganisms, and pressure should be considered as a
crucial factor in deep sea biodegradation studies.
7.5 Conclusions
The Deepwater Horizon (DWH) discharge is unique in that it occurred in the deep
sea, and unparalleled volumes of chemical dispersant were applied during emergency response efforts. A lack of knowledge on biodegradation in the deep sea hampered efforts to predict the fate and transport of released oil. Despite tremendous
progress, many knowledge gaps remain with regard to biodegradation under the
low-temperature and high-pressure conditions found in the deep ocean. Since biodegradation rates were not determined directly under in situ conditions, the role of
biodegradation as well as dispersant application on the fate and transport of petroleum hydrocarbons remains under debate. Hydrostatic pressure was shown to substantially impact biodegradation rates in both the water column and sediments of the
deep sea. However, as mentioned above, the field is in its infancy. Further investigations are warranted to improve understanding of pressure effects on the physiology
of deep sea hydrocarbon-degrading microorganisms, and pressure should be considered as a crucial factor in deep sea biodegradation studies. Direct rate measurements and determination of oceanographic controls such as pressure are sorely
needed to improve the effective parameterization of oil plume models. Ongoing
technological advances show potential to address these knowledge gaps.
J. E. Kostka et al.