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Biochemical studies on the fatty acid synthesis in relation to low-temperature adaptation in a psychrophilic bacterium, Vibrio sp. strain ABE-1

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Title: Biochemical studies on the fatty acid synthesis in relation to low-temperature adaptation in a psychrophilic bacterium, Vibrio sp. strain ABE-1
Other Titles: 好冷性細菌Vibrio sp. strain ABE-1の低温適応に関わる脂肪酸合成の生化学的研究
Authors: Morita, Naoki1 Browse this author
Authors(alt): 森田, 直樹1
Issue Date: 29-Sep-1995
Abstract: Vibrio sp. strain ABE-1 is a well-adapted microorganism to lowtemperature environment and characteristic of the capacity to regulate the membrane homeoviscously in a temperature range from 0℃ to 20℃. In order to understand the biochemical bases of the regulatry mechanisms of the membrane fluidity of psychrophilic microorganisms, fatty acid synthesis in Vibrio sp. strain ABE-1 was studied, with special emphasis on identification of determinating factors of fatty acid chain length and the capacity to synthesize unsaturated fatty acids. 1: Vibrio sp. strain ABE-1 had a type II FAS which had a capacity to synthesize, in addition to 16- and 18-carbon fatty acids, very long chain fatty acids with 20 up to 30 carbon atoms. This means that the FAS itself has no abililty to control the chain length of fatty acids. 2: The subfraction of cytosol which was prepared by 0% to 55% precipitation of ammonium sulfate had the activity of fatty acyl thioesterase. The fatty acyl thioesterase had higher affinity to acyl-ACP and acyl-CoA with 16-carbon fatty acids, suggesting that the chain length of fatty acids can be determined by the involvement of fatty acyl thioesterase. 3: ln Vibrio sp. strain ABE-1 mono-unsaturated fatty acids were synthesized under aerobic conditions not only via the anaerobic pathway by the type II FAS but also by aerobic desaturation of saturated fatty acid. This might explain the property of unsaturated fatty acid abundance in this bacterium. 4: Vibrio sp. strain ABE-1 synthesized significant level of 16:1(9t), when it was grown at 20℃, the upper limiting temperature for growth. The experiment using dideuterated 16:1(9c) and 16:1(9t) demonstrated that 16:1(9c) and 16:1(9t) are interconverted by cis-trans isomerlzatlon. 5. When Vibrio sp. strain ABE-1 was grown at 20℃, level of 16:1(9t) was increased and level of 16:0 was decreased at the late logarithmic phase where the capacity to synthesize 16:0 de novo was depressed. These results suggest that the lack of 16:0 can be compensated by appearance of 16:1(9t) in this bacterium. Thus, it was concluded that the involvement of specific fatty acyl thioesterase, the coexistance of the anaerobic pathway and the aerobic desaturation activity for the synthesis of unsaturated fatty acids, and the cis-trans isomerization of fatty acids would determine the characteristic profile of fatty acid in Vibrio sp. strain ABE-1.
Conffering University: 北海道大学
Degree Report Number: 甲第3712号
Degree Level: 博士
Degree Discipline: 理学
Type: theses (doctoral)
Appears in Collections:学位論文 (Theses) > 博士 (理学)

Submitter: 森田 直樹

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