Lipids in Cold-adapted Microorganisms
Ahmad Iskandar Bin Haji Mohd Taha, Rifat Zubair Ahmed, Taro Motoigi, Kentaro Watanabe, Norio Kurosawa and Hidetoshi Okuyama
from: Cold-Adapted Microorganisms (Edited by: Isao Yumoto). Caister Academic Press, U.K. (2013)
Ever since Escherichia coli, which is a mesophilic bacterium, was found to adjust its membrane fluidity in a liquid crystalline state by modulating fatty acid composition and the designation of this process as homeoviscous or homeophasic adaptation, numerous analogous phenomena have been reported in cold-adapted bacteria [psychrophilic or psychrotrophic (psychrotolerant) bacteria]. Unsaturation, which includes the biosynthesis of monounsaturated or long-chain polyunsaturated fatty acids and branched fatty acids, and branched-chain formation are the most important types of fatty acid modulation in psychrophilic and psychrotrophic (psychrotolerant) bacteria. The distribution of these fatty acids is not restricted to cold-adapted microorganisms: rather, it appears to depend on bacterial diversity (Gram- positive or negative) and/or habitat (terrestrial or marine environment) than on temperature. Eicosapentaenoic acid, which has been detected only in marine Gram-negative bacteria, had been regarded to confer significant membrane fluidity in bacteria, but it is now considered that it may also have a function in antioxidation or membrane modulation by constraining membrane fluidity. The mode of fatty acid modulation is unlikely to differ between psychrophilic and psychrotrophic bacteria, which had narrower and wider growth temperature ranges, respectively. The sole difference seems to be higher capacity to modulate fatty acid composition in psychrotrophic bacteria than in psychrophilic bacteria read more ...