Cellular and extracellular lipids of Acinetobacter lwoffi during growth on hexadecane

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Abstract
The cellular and extracellular lipid compositions of A. lwoffi [A. calcoaceticus] cultures were examined during diauxic growth on ethanol and hexadecane. Growth at the expense of ethanol resulted in proportionate increases in the main lipid components of A. lwoffi. After a prolonged lag phase following depletion of ethanol, growth at the expense of hexadecane resulted in an increase in phospholipids, but little change in the amounts of the other lipid species. The phospholipids were acylated, during growth on hexadecane, with larger proportions of palmitate and palmitoleate and smaller proportions of the C18 fatty acids. Due to tenacious binding of cells to the hexadecane remaining in the growth medium, it was impossible to obtain completely cell-free extracellular supernatants. Consequently, the levels of extracellular lipids were estimated as the difference between the actual amount of lipid measured in the supernatant and the amount theoretically associated with the bound cells. Using this approach, the extracellular lipids were found, during diauxie, to be present at levels similar to those formed in cultures grown on ethanol, in the absence of hydrocarbon. The lipid composition of the cell pellets and culture supernatants were relatively similar; hence, a disproportionate accumulation of 1 or more lipid species in the extracellular medium was not apparent.

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