Membrane fluidity and fatty acid comparisons in psychrotrophic and mesophilic strains of Acidithiobacillus ferrooxidans under cold growth temperatures

Psychrotrophic strains of Acidithiobacillus ferrooxidans have an important role inmetal leaching and acid mine drainage (AMD) production in colder mining environments. We investigated cytoplasmic membrane fluidity and fatty acid alterations in response to low temperatures (5 and 15\ub0C). Significant differences inmembrane fluidity,measured by polarization (P) of 1,6-diphenyl-1,3,5-hexatriene (DPH), were found where the psychrotrophic strains had a significantlymore rigidmembrane (P range =0.41\u20130.45) and lower transition temperature midpoints (Tm = 2.0\ub0C) and broader transition range than the mesophilic strains (P range = 0.38\u20130.39; Tm = 2.0\u201318\ub0C) at cold temperatures. Membrane remodeling was evident in all strains with a common trend of increased unsaturated fatty acid component in response to lower growth temperatures. In psychrotrophic strains, decreases in 12:0 fatty acids distinguished the 5\ub0C fatty acid profiles from those of the mesophilic strains that showed decreases in 16:0, 17:0, and cyclo-19:0 fatty acids. These changes were also correlated with the observed changes in membrane fluidity (R2 = 63\u201397%). Psychrotrophic strains employ distinctive modulation of cytoplasmic membrane fluidity with uncommon membrane phase changes as part of their adaptation to the extreme AMD environment in colder climates.Peer reviewed: YesNRC publication: Ye