Ethanolamine utilization in Salmonella typhimurium

Abstract

Ethanolamine can serve as the sole source of carbon and nitrogen for Salmonella typhimurium if vitamin B,2 is present to serve as a cofactor. The pathway for ethanolamine utilization has been investigated in order to understand its regulation and determine whether the pathway is important to the selective forces that have maintained the ability to synthesize B12 in S. typhimurium. We isolated mutants that are defective in ethanolamine utilization (eut mutants). These mutants defined a cluster of genes located between purC and cysA at 50 min on the Salmonella chromosome. A genetic map of the eut region was constructed. Included in the map are mutations which affect ethanolamine ammonia lyase, the first degradative enzyme, and mutations which affect the second enzyme in the pathway, acetaldehyde dehydrogenase. Transcriptional regulation of the eat genes was studied by using eut-lac operon fusions created by insertion of Mu d lac. Transcription is induced by the simultaneous presence of ethanolamine and B12 in the growth medium. The eut genes constitute a single unit of transcription. One class of mutations located at the promoter-distal end of the eut operon prevent induction of transcription.

Host Specificity of Bacterial Pathogens

“…This pathway is degraded in specialists S. Paratyphi C (eutA, eutC, eutK, and eutN) and S. Choleraesuis (eutN) (Liu et al 2009). Growth on ethanolamine under anaerobic conditions necessitates biosynthesis of vitamin B12 by the cob/cbi gene cluster (Roof and Roth 1988), which contains pseudogenes in S. Typhi (cbiM, cbiK, cbiJ, and cbiC), S. Paratyphi A (cbiA), and S. Gallinarum (cobD, cbiD, and cbiC) McClelland et al 2004;Thomson et al 2008).…”

Multiple posttranscriptional regulatory mechanisms partner to control ethanolamine utilization in Enterococcus faecalis

“…Ethanolamine is a product of the catabolism of phosphatidylethanolamine, an abundant phospholipid in both mammalian and bacterial membranes (3,4). Both the host diet and cells within the intestine (bacterial and epithelial) are thought to provide a rich ethanolamine source (5). Correspondingly, several bacterial species found within the GI tract encode the machinery necessary for ethanolamine catabolism, including, but not limited to, E. faecalis, Streptococcus sanguinis, Escherichia coli, and Salmonella, Listeria, and Clostridium species.…”

“…The process highly depends on bioavailability of adenosylcobalamin (AdoCbl), because the central enzymatic step requires AdoCbl as a cofactor (13). Expression of these genes in Salmonella is positively regulated by a DNA-binding transcription factor, EutR, encoded within the eut operon and active in the presence of AdoCbl and ethanolamine (5,14). E. faecalis lacks the EutR regulator, suggesting the existence of alternative regulatory mechanisms for control of ethanolamine catabolism (10).…”

The control region of the pdu/cob regulon in Salmonella typhimurium

“…Homocysteine methyl transferase (metH) transfers a methyl group from N-5-methyltetrahydrofolate to convert L-homocysteine to L-methionine (36). Ethanolamine ammonia-lyase cleaves ethanolamine to acetaldehyde and ammonia (32,33). Queuosine synthetase reduces epoxyqueuosine to queuosine, a modified base found in four tRNAs (17).…”