Rhamnose catabolism in Bacteroides thetaiotaomicron is controlled by the positive transcriptional regulator RhaR.
Bacteroides thetaiotaomicron is an important human gut commensal, which also causes opportunistic infections outside this environment. It utilises a range of host and diet-related carbohydrates, including rhamnose. In this study, the rha gene cluster, required for rhamnose utilisation, was characterised by transcription analysis, gene targeted mutagenesis and enzyme assays. Growth in the presence of L-rhamnose induced transcription of all the genes of this cluster. The first five genes of the cluster, rhaKIPAO, were transcribed as an operon from a transcriptional start site upstream of rhaK, whereas the sixth gene, rhaR, was transcribed independently. Bioinformatic analysis and mutation of the rhaR gene identified it as encoding the positive transcriptional activator of rhaKIPAO. A rhaR mutant could not utilise rhamnose as the sole carbon source but grew normally on glucose. The rhaO gene encoded a lactaldehyde reductase, and a rhaO mutant produced reduced levels of L-1,2-propanediol during growth in rhamnose, indicating its contribution to rhamnose catabolism in Bacteroides thetaiotaomicron.
Patel
Ekta H
EH
Department of Molecular and Cellular Biology, University of Cape Town, Rondebosch, Private Bag, 7701 Cape Town, South Africa. e.patel@cgiar.org
Paul
Lynthia V
LV
Patrick
Sheila
S
Abratt
Valerie R
VR
D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001439:Bacteroides / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D001483:Base Sequence; D019295:Computational Biology; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D011409:Propylene Glycols / Q000378:metabolism; D012210:Rhamnose / Q000378:metabolism*; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation
D001426:Bacterial Proteins; D011409:Propylene Glycols; D015534:Trans-Activators; D000429:Alcohol Oxidoreductases; C021494:lactaldehyde reductase; D012210:Rhamnose