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A Novel Electrophototrophic Bacterium Rhodopseudomonas palustris Strain RP2, Exhibits Hydrocarbonoclastic Potential in Anaerobic Environments.

Venkidusamy K, Megharaj M - Front Microbiol (2016)

Bottom Line: Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments.The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m(2); power density 720 ± 7 μW/m(2), 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l(-1) of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS.Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments.

View Article: PubMed Central - PubMed

Affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SAAustralia; CRC for Contamination Assessment and Remediation of the Environment, Mawson Lakes, SAAustralia.

ABSTRACT
An electrophototrophic, hydrocarbonoclastic bacterium Rhodopseudomonas palustris stain RP2 was isolated from the anodic biofilms of hydrocarbon fed microbial electrochemical remediation systems (MERS). Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments. In acetate fed microbial electrochemical cells, a maximum current density of 305 ± 10 mA/m(2) (1000Ω) was generated (power density 131.65 ± 10 mW/m(2)) by strain RP2 with a coulombic efficiency of 46.7 ± 1.3%. Cyclic voltammetry studies showed that anaerobically grown cells of strain RP2 is electrochemically active and likely to transfer electrons extracellularly to solid electron acceptors through membrane bound compounds, however, aerobically grown cells lacked the electrochemical activity. The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m(2); power density 720 ± 7 μW/m(2), 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l(-1) of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS. Here, we also report the first study that shows an initial evidence for the existence of a hydrocarbonoclastic behavior in the strain RP2 when grown in different electron accepting and illuminated conditions (anaerobic and MERS degradation). Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments. Identification of such novel petrochemical hydrocarbon degrading electricigens, not only expands the knowledge on the range of bacteria known for the hydrocarbon bioremediation but also shows a biotechnological potential that goes well beyond its applications to MERS.

No MeSH data available.


Related in: MedlinePlus

(A) Photoorganotrophic hydrocarbon degradation under different electron accepting conditions (PS-photosynthetic; PS+N- Photosynthetic + Nitrate; PS+S; Photosynthetic + Sulfate; PS+Fe- Photosynthetic + Iron). (B) A representative current density cycle of diesel fed microbial fuel cell system using strain RP2. (C) Hydrocarbon degradation under different reactor operating conditions (AC, Abiotic controls; OC, Open circuit controls; CC- Closed Circuit).
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Figure 6: (A) Photoorganotrophic hydrocarbon degradation under different electron accepting conditions (PS-photosynthetic; PS+N- Photosynthetic + Nitrate; PS+S; Photosynthetic + Sulfate; PS+Fe- Photosynthetic + Iron). (B) A representative current density cycle of diesel fed microbial fuel cell system using strain RP2. (C) Hydrocarbon degradation under different reactor operating conditions (AC, Abiotic controls; OC, Open circuit controls; CC- Closed Circuit).

Mentions: To study the hydrocarbon degradation potential of the strain RP2, experiments were performed under four different environments: oxic, anoxic, photosynthetic, and chemosynthetic. Cultures were inoculated into Wolfe’s media with DRHs as a sole carbon source with different electron accepting conditions. These incubation experiments indicate that photosynthetic anaerobic degradation of hydrocarbons occurred, however, no increase in biomass or hydrocarbon degradation was observed in chemosynthetically grown anaerobic or aerobic samples. The rate and extent of biodegradation was interpreted from GC chromatograms of the residual hydrocarbons. Figure 6A shows the possible anoxic photoheterotrophic degradation of DRH compounds under different electron accepting conditions [Photosynthetic only (PS); Photosynthetic + Nitrate (PS+N); Photosynthetic + Sulfate (PS+S); Photosynthetic + Iron (PS+Fe)]. For a substrate concentration of 4000 mg/l, cells showed ~10 to 30% of DRH removal by the end of the experiment. A higher percentage of DRH removal (30.6 ± 0.68%, 90th day) was noticed in the triplicates of sulfate containing anoxic, photoheterotrophic samples. Abiotic loss of DRH was measured under each condition was less than 5%.


A Novel Electrophototrophic Bacterium Rhodopseudomonas palustris Strain RP2, Exhibits Hydrocarbonoclastic Potential in Anaerobic Environments.

Venkidusamy K, Megharaj M - Front Microbiol (2016)

(A) Photoorganotrophic hydrocarbon degradation under different electron accepting conditions (PS-photosynthetic; PS+N- Photosynthetic + Nitrate; PS+S; Photosynthetic + Sulfate; PS+Fe- Photosynthetic + Iron). (B) A representative current density cycle of diesel fed microbial fuel cell system using strain RP2. (C) Hydrocarbon degradation under different reactor operating conditions (AC, Abiotic controls; OC, Open circuit controls; CC- Closed Circuit).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940424&req=5

Figure 6: (A) Photoorganotrophic hydrocarbon degradation under different electron accepting conditions (PS-photosynthetic; PS+N- Photosynthetic + Nitrate; PS+S; Photosynthetic + Sulfate; PS+Fe- Photosynthetic + Iron). (B) A representative current density cycle of diesel fed microbial fuel cell system using strain RP2. (C) Hydrocarbon degradation under different reactor operating conditions (AC, Abiotic controls; OC, Open circuit controls; CC- Closed Circuit).
Mentions: To study the hydrocarbon degradation potential of the strain RP2, experiments were performed under four different environments: oxic, anoxic, photosynthetic, and chemosynthetic. Cultures were inoculated into Wolfe’s media with DRHs as a sole carbon source with different electron accepting conditions. These incubation experiments indicate that photosynthetic anaerobic degradation of hydrocarbons occurred, however, no increase in biomass or hydrocarbon degradation was observed in chemosynthetically grown anaerobic or aerobic samples. The rate and extent of biodegradation was interpreted from GC chromatograms of the residual hydrocarbons. Figure 6A shows the possible anoxic photoheterotrophic degradation of DRH compounds under different electron accepting conditions [Photosynthetic only (PS); Photosynthetic + Nitrate (PS+N); Photosynthetic + Sulfate (PS+S); Photosynthetic + Iron (PS+Fe)]. For a substrate concentration of 4000 mg/l, cells showed ~10 to 30% of DRH removal by the end of the experiment. A higher percentage of DRH removal (30.6 ± 0.68%, 90th day) was noticed in the triplicates of sulfate containing anoxic, photoheterotrophic samples. Abiotic loss of DRH was measured under each condition was less than 5%.

Bottom Line: Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments.The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m(2); power density 720 ± 7 μW/m(2), 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l(-1) of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS.Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments.

View Article: PubMed Central - PubMed

Affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SAAustralia; CRC for Contamination Assessment and Remediation of the Environment, Mawson Lakes, SAAustralia.

ABSTRACT
An electrophototrophic, hydrocarbonoclastic bacterium Rhodopseudomonas palustris stain RP2 was isolated from the anodic biofilms of hydrocarbon fed microbial electrochemical remediation systems (MERS). Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments. In acetate fed microbial electrochemical cells, a maximum current density of 305 ± 10 mA/m(2) (1000Ω) was generated (power density 131.65 ± 10 mW/m(2)) by strain RP2 with a coulombic efficiency of 46.7 ± 1.3%. Cyclic voltammetry studies showed that anaerobically grown cells of strain RP2 is electrochemically active and likely to transfer electrons extracellularly to solid electron acceptors through membrane bound compounds, however, aerobically grown cells lacked the electrochemical activity. The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m(2); power density 720 ± 7 μW/m(2), 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l(-1) of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS. Here, we also report the first study that shows an initial evidence for the existence of a hydrocarbonoclastic behavior in the strain RP2 when grown in different electron accepting and illuminated conditions (anaerobic and MERS degradation). Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments. Identification of such novel petrochemical hydrocarbon degrading electricigens, not only expands the knowledge on the range of bacteria known for the hydrocarbon bioremediation but also shows a biotechnological potential that goes well beyond its applications to MERS.

No MeSH data available.


Related in: MedlinePlus