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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

Anode micrographs of R. palustris strain RP2 inoculated acetate-fed MFCs. (A) Treated control anode, (B) Strain RP2- biofilm on graphite surface and (C) Cells with high magnification.
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Figure 4: Anode micrographs of R. palustris strain RP2 inoculated acetate-fed MFCs. (A) Treated control anode, (B) Strain RP2- biofilm on graphite surface and (C) Cells with high magnification.

Mentions: Experiments were also conducted using dual chamber cubic MFCs (CMFC) containing carbon flat paper anodes at a fixed resistance of 1000 Ω. The voltage profile of the cubic MFC revealed that the voltage produced was less than that for the air cathode MFC. A long lag time was observed with the carbon paper anode whereas a treated brush anode reduced the strain acclimation period and resulted in an increased power generation. The maximum open circuit potential and power output of CMFC were 600 ± 7 mV and 70 mW/m2, respectively. Constant power and voltage output indicated the formation of a stable biofilm around the electrode surface. Scanning electron micrographs revealed that the bacterial population from the graphite brush anode was homogenous in shape (Figure 4).


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

Venkidusamy K, Megharaj M - Front Microbiol (2016)

Anode micrographs of R. palustris strain RP2 inoculated acetate-fed MFCs. (A) Treated control anode, (B) Strain RP2- biofilm on graphite surface and (C) Cells with high magnification.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 4: Anode micrographs of R. palustris strain RP2 inoculated acetate-fed MFCs. (A) Treated control anode, (B) Strain RP2- biofilm on graphite surface and (C) Cells with high magnification.
Mentions: Experiments were also conducted using dual chamber cubic MFCs (CMFC) containing carbon flat paper anodes at a fixed resistance of 1000 Ω. The voltage profile of the cubic MFC revealed that the voltage produced was less than that for the air cathode MFC. A long lag time was observed with the carbon paper anode whereas a treated brush anode reduced the strain acclimation period and resulted in an increased power generation. The maximum open circuit potential and power output of CMFC were 600 ± 7 mV and 70 mW/m2, respectively. Constant power and voltage output indicated the formation of a stable biofilm around the electrode surface. Scanning electron micrographs revealed that the bacterial population from the graphite brush anode was homogenous in shape (Figure 4).

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