The biosynthesis of wax esters in bacteria is accomplished by a unique pathway that combines a fatty alcohol and a fatty acyl coenzyme A substrate. Previous in vitro enzymatic studies indicated that two different enzymes could be involved in the synthesis of the required fatty alcohol in Marinobacter aquaeolei VT8. In this study, we demonstrate through a series of gene deletions and transcriptional analysis that either enzyme is capable of fulfilling the role of providing the fatty alcohol required for wax ester biosynthesis in vivo, but evolution has clearly selected one of these, a previously characterized fatty aldehyde reductase, as the preferred enzyme to perform this reaction under typical wax ester-accumulating conditions. These results complement previous in vitro studies and provide the first glimpse into the role of each enzyme in vivo in the native organism.T he global cycle of oil is of interest from the standpoints of both energy and the environment, as efforts by humankind to obtain this valuable resource can result in substantial releases of crude oil through incidents such as the Deepwater Horizon oil spill of 2010 in the Gulf of Mexico. We also note that crude oil from natural deposits is routinely released into aqueous environments, such as the oceans, by natural processes where geological reserves meet surface waters. These environments have allowed natural populations of organisms, such as marine bacteria, to evolve to utilize these supplies, rich in reduced carbon, for use as a biological fuel source. A primary focus related to oil-degrading marine bacteria is the oxidation of these oils to meet energy requirements of the living cell. Interestingly, for certain marine bacteria found to utilize and degrade oils, these bacteria are also capable of producing natural lipids that have economic values similar to those obtained from harvesting sperm whales prior to the late 20th century, even when the bacteria are grown on simple organic acids or carbohydrates. We selected the marine bacterium Marinobacter aquaeolei VT8, which was isolated from an oil well off the coast of Vietnam (1), as a model bacterial species to study metabolic processes in an oil-metabolizing and neutral lipid-accumulating bacteria. In addition to growing on long-chain hydrocarbons, M. aquaeolei VT8 also produces a natural hydrocarbon, the wax ester, when grown on simple citric acid cycle intermediates, such as succinate or citrate, as the sole carbon source (1-3), indicating that all of the precursors required for the biosynthesis of wax ester are indigenous to this strain.Biosynthesis of wax esters is accomplished by the combination of several different enzymes. The wax ester synthase/acyl-coenzyme A (CoA):diacylglycerol acyltransferase (WS/DGAT) enzyme catalyzes the reaction of a fatty acyl-CoA substrate with a fatty alcohol (Fig. 1). While the fatty acyl-CoA utilized by the WS/ DGAT is proposed to come directly from the fatty acyl-CoA pool, the fatty alcohol is believed to be produced through the action of several reducta...

The utility of specific strains of natural algicidal bacteria isolated from shallow wetland sediments was evaluated against several strains of algae with potential immediate or future commercial value. Two strains of bacteria, Pseudomonas pseudoalcaligenes AD6 and Aeromonas hydrophila AD9, were identified and demonstrated to have algicidal activity against the microalgae Neochloris oleoabundans and Dunaliella tertiolecta. These bacteria were further evaluated for the potential to improve lipid extraction using a mild solvent extraction approach. Aeromonas hydrophila AD9 showed a nearly 12-fold increase in lipid extraction with D. tertiolecta, while both bacteria showed a sixfold improvement in lipid extraction with N. oleoabundans.

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