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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

Cyclic Voltammetry studies of R. palustris strain RP2. (A) Anoxic grown cells; (B) Aerobically grown cells; Scan rate: 5 mV s-1.
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Figure 5: Cyclic Voltammetry studies of R. palustris strain RP2. (A) Anoxic grown cells; (B) Aerobically grown cells; Scan rate: 5 mV s-1.

Mentions: Cell suspensions were prepared from the bacterial cells grown under anaerobic and aerobic environments to determine the electrochemical activities of the strain RP2 using cyclic voltammetry (CV) studies. Oxidation and reduction peaks of CV were observed in anaerobic grown bacterial cells (Figure 5A) whereas aerobically grown cells lacked the electrochemical activity (Figure 5B). Reduction peaks ranging from -394 mV to -399 mV and oxidation peaks ranging from -200 mV to +100 mV were observed at the electrode interface from washed cells suspensions. The calculated mid-point potential was about -278 mV. This asymmetric CV peak shows that the redox reaction is a quasi-reversible reaction. The amplitude of the peaks increased according to the growth stage of the culture in batch mode. The highest peaks were present during the exponential growth stage which indicated that the development of biofilm was the main factor for the electron transfer. One redox couple was observed from the CV peak and number of electrons transferred was calculated based on the Nernst equation (Logan, 2008). The CV peaks were not observed from the suspension of aerobically grown cells or autoclaved controls.


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

Venkidusamy K, Megharaj M - Front Microbiol (2016)

Cyclic Voltammetry studies of R. palustris strain RP2. (A) Anoxic grown cells; (B) Aerobically grown cells; Scan rate: 5 mV s-1.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 5: Cyclic Voltammetry studies of R. palustris strain RP2. (A) Anoxic grown cells; (B) Aerobically grown cells; Scan rate: 5 mV s-1.
Mentions: Cell suspensions were prepared from the bacterial cells grown under anaerobic and aerobic environments to determine the electrochemical activities of the strain RP2 using cyclic voltammetry (CV) studies. Oxidation and reduction peaks of CV were observed in anaerobic grown bacterial cells (Figure 5A) whereas aerobically grown cells lacked the electrochemical activity (Figure 5B). Reduction peaks ranging from -394 mV to -399 mV and oxidation peaks ranging from -200 mV to +100 mV were observed at the electrode interface from washed cells suspensions. The calculated mid-point potential was about -278 mV. This asymmetric CV peak shows that the redox reaction is a quasi-reversible reaction. The amplitude of the peaks increased according to the growth stage of the culture in batch mode. The highest peaks were present during the exponential growth stage which indicated that the development of biofilm was the main factor for the electron transfer. One redox couple was observed from the CV peak and number of electrons transferred was calculated based on the Nernst equation (Logan, 2008). The CV peaks were not observed from the suspension of aerobically grown cells or autoclaved controls.

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