Identification of a Novel N-Acetylmuramic Acid Transporter in Tannerella forsythia.
Tannerella forsythia is a Gram-negative periodontal pathogen lacking the ability to undergo de novo synthesis of amino sugars N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) that form the disaccharide repeating unit of the peptidoglycan backbone. T. forsythia relies on the uptake of these sugars from the environment, which is so far unexplored. Here, we identified a novel transporter system of T. forsythia involved in the uptake of MurNAc across the inner membrane and characterized a homolog of the Escherichia coli MurQ etherase involved in the conversion of MurNAc-6-phosphate (MurNAc-6-P) to GlcNAc-6-P. The genes encoding these components were identified on a three-gene cluster spanning Tanf_08375 to Tanf_08385 located downstream from a putative peptidoglycan recycling locus. We show that the three genes, Tanf_08375, Tanf_08380, and Tanf_08385, encoding a MurNAc transporter, a putative sugar kinase, and a MurQ etherase, respectively, are transcriptionally linked. Complementation of the Tanf_08375 and Tanf_08380 genes together in trans, but not individually, rescued the inability of an E. coli mutant deficient in the phosphotransferase (PTS) system-dependent MurNAc transporter MurP as well as that of a double mutant deficient in MurP and components of the PTS system to grow on MurNAc. In addition, complementation with this two-gene construct in E. coli caused depletion of MurNAc in the medium, further confirming this observation. Our results show that the products of Tanf_08375 and Tanf_08380 constitute a novel non-PTS MurNAc transporter system that seems to be widespread among bacteria of the Bacteroidetes phylum. To the best of our knowledge, this is the first identification of a PTS-independent MurNAc transporter in bacteria.



In this study, we report the identification of a novel transporter for peptidoglycan amino sugar N-acetylmuramic acid (MurNAc) in the periodontal pathogen T. forsythia It has been known since the late 1980s that T. forsythia is a MurNAc auxotroph relying on environmental sources for this essential sugar. Most sugar transporters, and the MurNAc transporter MurP in particular, require a PTS phosphorelay to drive the uptake and concurrent phosphorylation of the sugar through the inner membrane in Gram-negative bacteria. Our study uncovered a novel type of PTS-independent MurNAc transporter, and although so far, it seems to be unique to T. forsythia, it may be present in a range of bacteria both of the oral cavity and gut, especially of the phylum Bacteroidetes.
Department of Oral Biology, University at Buffalo, Buffalo, New York, USA.
Angela
A
Ruscitto
Interfaculty Institute of Microbiology and Infection Medicine Tübingen, IMIT, Department of Microbiology & Biotechnology, University of Tübingen, Tübingen, Germany.
Isabel
I
Hottmann
Oral and Maxillofacial Pathology, University of Sheffield, Sheffield, United Kingdom.
Graham P
GP
Stafford
Department for NanoBiotechnology, NanoGlycobiology Unit, Universität für Bodenkultur Wien, Vienna, Austria.
Christina
C
Schäffer
Interfaculty Institute of Microbiology and Infection Medicine Tübingen, IMIT, Department of Microbiology & Biotechnology, University of Tübingen, Tübingen, Germany christoph.mayer@uni-tuebingen.de sharmaa@buffalo.edu.
Christoph
C
Mayer
Department of Oral Biology, University at Buffalo, Buffalo, New York, USA christoph.mayer@uni-tuebingen.de sharmaa@buffalo.edu.
Ashu
A
Sharma
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009112:Muramic Acids / Q000378:metabolism*; D010457:Peptidoglycan / Q000378:metabolism; D000070436:Tannerella forsythia / Q000201:enzymology / Q000235:genetics*
D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D009112:Muramic Acids; D010457:Peptidoglycan; C031651:N-acetylmuramic acid; D006026:Glycoside Hydrolases