Abel, K. (Melpar, Inc., Falls Church, Va.), H. deSchmertzing, and J. I. Peterson. Classification of microorganisms by analysis of chemical composition. I. Feasibility of utilizing gas chromatography. J. Bacteriol. 85:1039-1044. 1963.-The feasibility of utilizing gas chromatography as a sensitive and rapid method for the analysis of lipids as a natural basis for the classification of microorganisms by chemical composition was investigated. The lipids were extracted and transesterified to component carboxylic acid methyl esters in a single step, after which the methyl esters were resolved by gas chromatography to provide distinctive chromatographic elution patterns. Similarities in the lipid carboxylic acid distribution were noted among selected species of the family Enterobacteriaceae, and significant differences were noted among selected families of the class Schizomycetes.