Biosynthesis of Lipids

Microbial membranes exhibit diverse lipid compositions across bacteria, archaea, and eukarya, reflecting distinct evolutionary adaptations.

Bacteria and eukarya synthesize fatty acids from acetyl-CoA and malonyl-CoA via the fatty acid synthase pathway, which involves condensation, reduction, and dehydration.

In contrast, archaea produce isoprenoid lipids from isopentenyl pyrophosphate via the mevalonate phosphate pathway.

In bacteria and eukarya, fatty acids are linked to glycerol via ester bonds, forming phospholipids such as phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin, contributing to membrane integrity and function.

Archaea, lacking fatty acids, possess ether-linked isoprenoid lipids for stability in extreme conditions.

Their biosynthesis assembles precursors like isopentenyl and dimethylallyl pyrophosphate into isoprenoids, including carotenoids and polyisoprenoid lipids.

Some bacteria, such as Bradyrhizobium and Streptomyces, use these isoprenoid precursors to synthesize squalene, which cyclizes into membrane-stabilizing hopanoids.

Eukaryotes use the same precursors to synthesize sterols like cholesterol, which regulate membrane fluidity.