Photobiological transformation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) using Rhodobacter sphaeroides.
Pump-and-treat strategies for groundwater containing explosives may be necessary when the contaminated water approaches sensitive receptors. This project investigated bacterial photosynthesis as a strategy for ex situ treatment, using light as the primary energy source to facilitate RDX transformation. The objective was to characterize the ability of photosynthetic Rhodobacter sphaeroides (strain ATCC(®) 17023 ™) to transform the high-energy explosive RDX. R. sphaeroides transformed 30 μM RDX within 40 h under light conditions; RDX was not fully transformed in the dark (non-photosynthetic conditions), suggesting that photosynthetic electron transfer was the primary mechanism. Experiments with RDX demonstrated that succinate and malate were the most effective electron donors for photosynthesis, but glycerol was also utilized as a photosynthetic electron donor. RDX was transformed irrespective of the presence of carbon dioxide. The electron shuttling compound anthraquinone-2,6-disulfonate (AQDS) increased transformation kinetics in the absence of CO2, when the cells had excess NADPH that needed to be re-oxidized because there was limited CO2 for carbon fixation. When CO2 was added, the cells generated more biomass, and AQDS had no stimulatory effect. End products indicated that RDX carbon became CO2, biomass, and a soluble, uncharacterized aqueous metabolite, determined using (14)C-labeled RDX. These data are the first to suggest that photobiological explosives transformation is possible and will provide a framework for which phototrophy can be used in environmental restoration of explosives contaminated water.
Environmental Engineering and Earth Sciences, Clemson University, 312 Biosystems Research Complex, Clemson, SC 29634, United States; Department of Civil, Environmental & Construction Engineering, Texas Tech University, Lubbock, TX 79409, United States.
Kayleigh A
KA
Millerick
Environmental Engineering and Earth Sciences, Clemson University, 312 Biosystems Research Complex, Clemson, SC 29634, United States.
Juliet T
JT
Johnston
Environmental Engineering and Earth Sciences, Clemson University, 312 Biosystems Research Complex, Clemson, SC 29634, United States. Electronic address: ktf@clemson.edu.
Kevin T
KT
Finneran
D000880:Anthraquinones / Q000494:pharmacology; D001673:Biodegradation, Environmental / Q000187:drug effects / Q000528:radiation effects; D053834:Explosive Agents / Q000378:metabolism*; D007700:Kinetics; D008027:Light; D008293:Malates / Q000494:pharmacology; D010084:Oxidation-Reduction; D012242:Rhodobacter sphaeroides / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects*; D019802:Succinic Acid / Q000494:pharmacology; D014227:Triazines / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
D000880:Anthraquinones; D053834:Explosive Agents; D008293:Malates; D014227:Triazines; D014874:Water Pollutants, Chemical; C408124:anthraquinone-2,6-disulfonate; C030298:malic acid; D019802:Succinic Acid; C009160:cyclonite
Biodegradation; Cyclic nitramine explosives; Photosynthesis; Rhodobacter sphaeroides