Role of lipids in theNeurospora crassa membrane

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Abstract
The effect of doubling the saturated fatty acid content on the electrophysiology ofNeurospora crassa membranes was studied. Intracellular membrane input resistance (R m ) and potential (E m ) were measured for wild-type (w/t) andcel − (Tween 40) organisms as a function of temperature. Over the 0 to 40°C temperature range studied, meanE m values of bothw/t andcel − (Tw 40) organisms increased from −160 to −210 mV. This difference is greater than that expected from Nernst potential considerations, indicating an active component ofE m . This active component is insensitive to a doubling of the saturated fatty acid content.R m exhibits a temperature dependence and hysteresis. Averaged data indicate an increase inR m with decreased temperature. The slope of the temperature dependence varies among individual hyphae. Above 17.5°Ccel − (Tw 40) hyphae averaged greater than 70% higher values ofR m thanw/t. Below 17.5°Cw/t R m data divided into low and high temperature dependence groups, whilecel − data exhibited a low temperature dependence. The results are discussed in relation to gel-liquid crystal phase transitions, membrane fluidity, and the contribution of fatty acid structure to membrane electrical properties.

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