Two putative Enterococcus faecalis fabG genes do not encode β-ketoacyl-acyl carrier protein reductases

<i>Enterococcus faecalis</i> encodes three putative <i>Escherichia coli</i> β-ketoacyl-acyl carrier protein (ACP) reductases (FabG). The <i>fabG1</i> gene is located within the operon that encodes most of the fatty acid synthesis genes, while the putative <i>fabG2</i> and <i>fabG3</i> genes are located elsewhere on the chromosome. The genes were tested for the ability to complement the growth of an <i>E. coli fabG</i>(Ts) strain at the non-permissive temperature. Of the three genes, only <i>E. faecalis</i> FabG1 restored growth at high temperature. Moreover, deletion of the <i>E. faecalis fabG1</i> gene resulted in an auxotrophic strain that required oleic acid for growth, arguing that it encodes the only functional β-ketoacyl-ACP reductase. Growth of this strain in the absence of fatty acid was restored by plasmid-borne <i>fabG1</i>, but not by plasmids encoding either <i>fabG2</i> or <i>fabG3</i>. Although <i>E. faecalis fabG2</i> has a putative binding site for the FabT transcription factor at the 5' end of the coding region, expression of a transcriptional fusion with β-galactosidase was unaffected by deletion of <i>fabT</i> or by fatty acid supplementation.