Temperature-sensitive mutants of Escherichia coli requiring saturated and unsaturated fatty acids for growth: isolation and properties.

A procedure is described for selection of temperature-sensitive mutants affecting fatty-acid synthesis based upon radiation suicide of wild-type organisms by tritiated acetate selectively incorporated into fatty acids. At 37 degrees , two of the mutants extensively incorporate fatty-acid supplements provided in the medium, and grow for extended periods only when a trans-unsaturated or a combination of saturated and cis-unsaturated fatty acids is available. In vivo fatty-acid synthesis, measured by [(14)C]acetate incorporation, is temperature-sensitive in these strains relative to protein synthesis and other non-lipid macromolecular syntheses using acetate. The biochemical nature of these mutations has not been identified.