Fatty acid transport by the lipophilic bacterium Nocardia asteroides

Abstract

Hexadecanoate was translocated in N. asteroides by a constitutive transport system(s), which transported short-, medium- and long-chain fatty acids. Inhibition of hexadecanoate transport by homologues suggested that at least 2 systems are present: 1 specific for short-chain fatty acids and the other specific for medium- and long-chain fatty acids. Saturation kinetics typical of a carrier-mediated transport system (Kt = 870 .mu.M) were observed and concentration of fatty acids against a gradient was achieved. Inhibitor studies indicated that free sulfhydryl groups, a functional respiratory chain and energy are required for translocation. Efflux of [14C]hexadecanoate in the presence of excess unlabeled hexadecanoate or 2,4-dinitrophenol and the cytoplasmic localization of acyl-CoA synthetase (acid:CoA ligase [AMP]; EC 6.2.1.3) are consistent with the hypothesis that fatty acids are transported and released intracellularly as free fatty acids.