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Microbiology 151 (2005), 113-119; DOI  10.1099/mic.0.27651-0
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Microbiology 151 (2005), 113-119; DOI  10.1099/mic.0.27651-0
© 2005 Society for General Microbiology

Temperature adaptation in Dictyostelium: role of {Delta}5 fatty acid desaturase

Tamao Saito1, Atsushi Kato1, Hiroshi Ochiai1 and Naoki Morita2

1 Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, 060-0810 Japan
2 Research Institute of Genome-based Biofactory, National Institute of Advanced Industrial Science and Technology (AIST), Toyohira-ku, Sapporo 062-8517 Japan

Correspondence
Tamao Saito
tasaito{at}sci.hokudai.ac.jp

Membrane fluidity is critical for proper membrane function and is regulated in part by the proportion of unsaturated fatty acids present in membrane lipids. The proportion of these lipids in turn varies with temperature and may contribute to temperature adaptation in poikilothermic organisms. The fundamental question posed in this study was whether the unsaturation of fatty acids contributes to the ability to adapt to temperature stress in Dictyostelium. First, fatty acid composition was analysed and it was observed that the relative proportions of dienoic acids changed with temperature. To investigate the role of dienoic fatty acids in temperature adaptation, null mutants were created in the two known {Delta}5 fatty acid desaturases (FadA and FadB) that are responsible for the production of dienoic fatty acids. The fadB null mutant showed no significant alteration in fatty acid composition or in phenotype. However, the disruption of fadA resulted in a large drop in dienoic fatty acid content from 51·2 to 4·1 % and a possibly compensatory increase in monoenoic fatty acids (40·9–92·4 %). No difference was detected in temperature adaptation with that of wild-type cells during the growth phase. However, surprisingly, mutant cells developed more efficiently than the wild-type at elevated temperatures. These results show that the fatty acid composition of Dictyostelium changes with temperature and suggest that the regulation of dienoic fatty acid synthesis is involved in the development of Dictyostelium at elevated temperatures, but not during the growth phase.

Nomenclature: Cx : y(a,b), a fatty acid containing x carbon atoms and y double bonds – the numbers in parentheses (a,b) indicate the position of the double bonds; des5-1 and des5-2 genes have been renamed as fadA and fadB, respectively, according to the recommended genetic nomenclature for Dictyostelium.






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