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Effect of high pressure on hydrocarbon-degrading bacteria.

Schedler M, Hiessl R, Valladares Juárez AG, Gust G, Müller R - AMB Express (2014)

Bottom Line: However, above this pressure growth decreased and at 12 MPa or more no more growth was observed.Nevertheless, S. yanoikuyae continued to convert naphthalene at pressure >12 MPa, although at a lower rate than at 0.1 MPa.These results show that high pressure has a strong influence on the biodegradation of crude oil components and that, contrary to previous assumptions, the role of pressure cannot be discounted when estimating the biodegradation and ultimate fate of deep-sea oil releases such as the Deepwater Horizon event.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Technical Biocatalysis, Hamburg University of Technology, Hamburg 21073, Germany.

ABSTRACT
The blowout of the Deepwater Horizon in the Gulf of Mexico in 2010 occurred at a depth of 1500 m, corresponding to a hydrostatic pressure of 15 MPa. Up to now, knowledge about the impact of high pressure on oil-degrading bacteria has been scarce. To investigate how the biodegradation of crude oil and its components is influenced by high pressures, like those in deep-sea environments, hydrocarbon degradation and growth of two model strains were studied in high-pressure reactors. The alkane-degrading strain Rhodococcus qingshengii TUHH-12 grew well on n-hexadecane at 15 MPa at a rate of 0.16 h(-1), although slightly slower than at ambient pressure (0.36 h(-1)). In contrast, the growth of the aromatic hydrocarbon degrading strain Sphingobium yanoikuyae B1 was highly affected by elevated pressures. Pressures of up to 8.8 MPa had little effect on growth of this strain. However, above this pressure growth decreased and at 12 MPa or more no more growth was observed. Nevertheless, S. yanoikuyae continued to convert naphthalene at pressure >12 MPa, although at a lower rate than at 0.1 MPa. This suggests that certain metabolic functions of this bacterium were inhibited by pressure to a greater extent than the enzymes responsible for naphthalene degradation. These results show that high pressure has a strong influence on the biodegradation of crude oil components and that, contrary to previous assumptions, the role of pressure cannot be discounted when estimating the biodegradation and ultimate fate of deep-sea oil releases such as the Deepwater Horizon event.

No MeSH data available.


Related in: MedlinePlus

High-pressure reactors and control reactors. High-pressure reactors (right, made from stainless steel and bronze, max. pressure 40 MPa, pressurizing with N2 gas, 160 mL volume) and aluminum control reactors (left, max. 0.1 MPa, 160 mL volume) were used for cultivation of hydrocarbon degraders at high and ambient pressure. The cultures were mixed with magnetic stirrers.
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Figure 1: High-pressure reactors and control reactors. High-pressure reactors (right, made from stainless steel and bronze, max. pressure 40 MPa, pressurizing with N2 gas, 160 mL volume) and aluminum control reactors (left, max. 0.1 MPa, 160 mL volume) were used for cultivation of hydrocarbon degraders at high and ambient pressure. The cultures were mixed with magnetic stirrers.

Mentions: Ten high-pressure reactors consisting of stainless steel cylinders capped with bronze lids were used to simulate and to investigate biodegradation under elevated pressures as they occur in deep-sea environments. Additionally, ten aluminium reactors with the same geometry were used, serving as controls to monitor biodegradation under atmospheric pressure in simultaneous experiments (Figure 1). Both reactor types had a volume of 160 mL. For experiments with R. qingshengii TUHH-12, 20 mL mineral medium was filled into sterilized glass vials and supplemented with 1 mM n-hexadecane. For cultivation of S. yanoikuyae B1, 20 mL Brunner medium and 1.77 mM naphthalene were used. The amount of carbon in 1.77 mM naphthalene is equal to the amount of carbon in 1 mM n-hexadecane. The media were inoculated with a grown preculture of the respective bacterial strain, constituting 10% of the total volume. The vials were placed inside the reactors. The high-pressure reactors were pressurized with nitrogen gas up to 15 MPa (equivalent to 1,500 m DWH well depth). The cultures were incubated at room temperature. Since the oil components used in these experiments are nearly insoluble in water, stirring rates affect biodegradation rates; therefore, efficient mixing of the cultures was ensured by magnetic stirring at 200 rpm. Due to the immiscible two-phase system of oil and water and the impracticality of subsampling at high pressure, no representative samples could be taken from the reactors to monitor oil concentrations. Thus, for each point in time in a diagram the content of one reactor was processed. Before opening a reactor containing n-hexadecane, it was cooled for 5 h at 4°C to minimise evaporation of n-hexadecane. Bacterial growth was measured and the hydrocarbon concentrations were analysed to quantify the degree of biodegradation. In several repetitions of the experiments the effects of pressure were the same. Only slightly different growth and degradation rates were observed due to different sampling times and slightly differing inoculation cell numbers. Thus, the diagrams presented represent the typical course of growth and hydrocarbon degradation.


Effect of high pressure on hydrocarbon-degrading bacteria.

Schedler M, Hiessl R, Valladares Juárez AG, Gust G, Müller R - AMB Express (2014)

High-pressure reactors and control reactors. High-pressure reactors (right, made from stainless steel and bronze, max. pressure 40 MPa, pressurizing with N2 gas, 160 mL volume) and aluminum control reactors (left, max. 0.1 MPa, 160 mL volume) were used for cultivation of hydrocarbon degraders at high and ambient pressure. The cultures were mixed with magnetic stirrers.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230898&req=5

Figure 1: High-pressure reactors and control reactors. High-pressure reactors (right, made from stainless steel and bronze, max. pressure 40 MPa, pressurizing with N2 gas, 160 mL volume) and aluminum control reactors (left, max. 0.1 MPa, 160 mL volume) were used for cultivation of hydrocarbon degraders at high and ambient pressure. The cultures were mixed with magnetic stirrers.
Mentions: Ten high-pressure reactors consisting of stainless steel cylinders capped with bronze lids were used to simulate and to investigate biodegradation under elevated pressures as they occur in deep-sea environments. Additionally, ten aluminium reactors with the same geometry were used, serving as controls to monitor biodegradation under atmospheric pressure in simultaneous experiments (Figure 1). Both reactor types had a volume of 160 mL. For experiments with R. qingshengii TUHH-12, 20 mL mineral medium was filled into sterilized glass vials and supplemented with 1 mM n-hexadecane. For cultivation of S. yanoikuyae B1, 20 mL Brunner medium and 1.77 mM naphthalene were used. The amount of carbon in 1.77 mM naphthalene is equal to the amount of carbon in 1 mM n-hexadecane. The media were inoculated with a grown preculture of the respective bacterial strain, constituting 10% of the total volume. The vials were placed inside the reactors. The high-pressure reactors were pressurized with nitrogen gas up to 15 MPa (equivalent to 1,500 m DWH well depth). The cultures were incubated at room temperature. Since the oil components used in these experiments are nearly insoluble in water, stirring rates affect biodegradation rates; therefore, efficient mixing of the cultures was ensured by magnetic stirring at 200 rpm. Due to the immiscible two-phase system of oil and water and the impracticality of subsampling at high pressure, no representative samples could be taken from the reactors to monitor oil concentrations. Thus, for each point in time in a diagram the content of one reactor was processed. Before opening a reactor containing n-hexadecane, it was cooled for 5 h at 4°C to minimise evaporation of n-hexadecane. Bacterial growth was measured and the hydrocarbon concentrations were analysed to quantify the degree of biodegradation. In several repetitions of the experiments the effects of pressure were the same. Only slightly different growth and degradation rates were observed due to different sampling times and slightly differing inoculation cell numbers. Thus, the diagrams presented represent the typical course of growth and hydrocarbon degradation.

Bottom Line: However, above this pressure growth decreased and at 12 MPa or more no more growth was observed.Nevertheless, S. yanoikuyae continued to convert naphthalene at pressure >12 MPa, although at a lower rate than at 0.1 MPa.These results show that high pressure has a strong influence on the biodegradation of crude oil components and that, contrary to previous assumptions, the role of pressure cannot be discounted when estimating the biodegradation and ultimate fate of deep-sea oil releases such as the Deepwater Horizon event.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Technical Biocatalysis, Hamburg University of Technology, Hamburg 21073, Germany.

ABSTRACT
The blowout of the Deepwater Horizon in the Gulf of Mexico in 2010 occurred at a depth of 1500 m, corresponding to a hydrostatic pressure of 15 MPa. Up to now, knowledge about the impact of high pressure on oil-degrading bacteria has been scarce. To investigate how the biodegradation of crude oil and its components is influenced by high pressures, like those in deep-sea environments, hydrocarbon degradation and growth of two model strains were studied in high-pressure reactors. The alkane-degrading strain Rhodococcus qingshengii TUHH-12 grew well on n-hexadecane at 15 MPa at a rate of 0.16 h(-1), although slightly slower than at ambient pressure (0.36 h(-1)). In contrast, the growth of the aromatic hydrocarbon degrading strain Sphingobium yanoikuyae B1 was highly affected by elevated pressures. Pressures of up to 8.8 MPa had little effect on growth of this strain. However, above this pressure growth decreased and at 12 MPa or more no more growth was observed. Nevertheless, S. yanoikuyae continued to convert naphthalene at pressure >12 MPa, although at a lower rate than at 0.1 MPa. This suggests that certain metabolic functions of this bacterium were inhibited by pressure to a greater extent than the enzymes responsible for naphthalene degradation. These results show that high pressure has a strong influence on the biodegradation of crude oil components and that, contrary to previous assumptions, the role of pressure cannot be discounted when estimating the biodegradation and ultimate fate of deep-sea oil releases such as the Deepwater Horizon event.

No MeSH data available.


Related in: MedlinePlus