THE EFFECT OF ETHANOL AND OXYGEN ON THE GROWTH OF ZYMOMONAS-MOBILIS AND THE LEVELS OF HOPANOIDS AND OTHER MEMBRANE-LIPIDS

Zymomonas mobilis (ATCC 29191) was grown either aerobically or anaerob ically in the presence of 2% (wt/vol) glucose and 0, 3, or 6% (vol/vol ) ethanol. The rates of growth and the composition of hopanoids, cellu lar fatty acids, and other lipids in the bacterial membranes were quan titatively analyzed. The bacterium grew in the presence of 3% and 6% e thanol and was more ethanol tolerant when grown anaerobically. Ln the absence of ethanol, hopanoids comprised about 30% (by mass) of the tot al cellular lipids, Addition of ethanol to the media caused complex ch anges in the levels of hopanoids and other lipids. However, there was not a significant increase in any of the hopanoid lipid classes as eth anol concentration was increased. As previously reported, vaccenic aci d was the most abundant fatty acid in the lipids of Z. mobilis, and it s high constitutive levels were unaffected by the variations in ethano l and oxygen concentrations, A cyclopropane fatty acid accounted for 2 .6-6.4 wt % of the total fatty acids in all treatments.