Effect of temperature on membrane lipids of Pseudomonas veronii isolated from French alpine lakes

• Temperature adaptation of two Gram-negative bacterial strains isolated from Alpine lakes. • Non-linear response to temperature, relying mainly on non-hydroxy fatty acids. • The strains exhibit slight differences in temperature adaptation. 3-hydroxy fatty acids (3-OH FAs) produced by Gram-negative bacteria were recently proposed as promising temperature proxies. Nevertheless, the lipid adaptation mechanism of such microorganisms to temperature remains largely unexplored. Here, we investigated how growth temperature (5–25°C) affects lipid profiles of non-hydroxylated (non-OH) and 3-OH FAs in two Pseudomonas veronii strains isolated from French alpine lakes. Membrane adaptation to rising temperatures was mainly driven by non-OH-FAs, characterised by a higher saturated/unsaturated ratio, while 3-OH FA total proportion slightly increased from 12 to 15% of total FAs. FA profiles showed a non-linear response, with minor changes between 5 and 18°C cultivation temperature and a marked shift at 25°C, as well as slight differences between the two isolates. Our findings illustrate varied lipid response to temperature with potential implications in using 3-OH FAs as temperature proxies in lakes.