Enhancement of saturated fatty acid content in soil microbial membranes across natural and experimental warming gradients

Organisms including microorganisms from aquatic, grassland and glacier ecosystems have been found to regulate the lipid composition of their membranes to acclimate to warming. However, little evidence exists for whether soil microbes in forest ecosystems acclimate to temperature variations through this biochemical mechanism. Here, using phospholipid fatty acid (PLFA) analysis of forest soils subjected to seasonal, latitudinal, and artificial incubation temperature variations, we identified that the lipid composition of soil microbial cell membranes changed significantly with alterations in temperature. Specifically, saturated fatty acids without branches (SAFAs) increased while unsaturated fatty acids (UNFAs) decreased with increasing temperature in a linear fashion. The slope of SAFAs increase (or UNFAs decrease) with temperature was steeper for the long-existing latitudinal temperature gradient than for the short-term incubation temperature gradient, suggesting that longer-term warming may result in larger alterations in lipid constitute of soil microbial membranes. Our results provide evidence that forest soil microorganisms would preserve saturated fatty acids at warmer temperatures and therefore may acclimate to global warming by modifying the lipid composition of their cell membranes to adjust membrane fluidity.