What is a Fatty Acid?

The most basic definition for fatty acids is a class of compounds containing a long hydrocarbon chain with a terminal carboxylate group. The name is derived from the name of the parent hydrocarbon, and oic is substituted for the final e. Fatty acids are divided into two groups - straight chain and branched chain. The fatty acids that are important for bacterial identification are the branched chain fatty acids containing from 9 to 20 carbons.

Where do fatty acids occur?

Fatty acids in bacteria comprise a portion of the phospholipids in cell membranes and also occur in the lipopolysaccharides of cells. There are several different lipids that occur in the cell membrane.

Membrane Lipid Composition

In membranes, short chain length and unsaturation enhance the fluidity of fatty acids and their derivatives.

• Glycolipids are a sugar containing lipids. They consist of fatty acid chains and usually contain an even number of carbons. One or more sugar units are attached to the primary hydroxyl unit on the fatty acid.
• Phospohlipids are derived from either glycerol, a 3 carbon alcohol or sphingosine, a more complex alcohol. Phospholipids derived from glycerol are called phosphoglycerides. A phosphoglyceride consists of a glycerol backbone, two fatty acid chains, and a phosphorylated alcohol. An even number of carbon atoms ranging from 14 to 24 is typical.
• Sterols - cholesterol is present in eucaryotes but not in most procaryotes