title: Transport of D-xylose in Lactobacillus pentosus, Lactobacillus casei, and Lactobacillus plantarum: evidence for a mechanism of facilitated diffusion via the phosphoenolpyruvate:mannose phosphotransferase system.
abstract: We have identified and characterized the D-xylose transport system of Lactobacillus pentosus. Uptake of D-xylose was not driven by the proton motive force generated by malolactic fermentation and required D-xylose metabolism. The kinetics of D-xylose transport were indicative of a low-affinity facilitated-diffusion system with an apparent K(m) of 8.5 mM and a V(max) of 23 nmol min(-1) mg of dry weight(-1). In two mutants of L. pentosus defective in the phosphoenolpyruvate:mannose phosphotransferase system, growth on D-xylose was absent due to the lack of D-xylose transport. However, transport of the pentose was not totally abolished in a third mutant, which could be complemented after expression of the L. curvatus manB gene encoding the cytoplasmic EIIB(Man) component of the EII(Man) complex. The EII(Man) complex is also involved in D-xylose transport in L. casei ATCC 393 and L. plantarum 80. These two species could transport and metabolize D-xylose after transformation with plasmids which expressed the D-xylose-catabolizing genes of L. pentosus, xylAB. L. casei and L. plantarum mutants resistant to 2-deoxy-D-glucose were defective in EII(Man) activity and were unable to transport D-xylose when transformed with plasmids containing the xylAB genes. Finally, transport of D-xylose was found to be the rate-limiting step in the growth of L. pentosus and of L. plantarum and L. casei ATCC 393 containing plasmids coding for the D-xylose-catabolic enzymes, since the doubling time of these bacteria on D-xylose was proportional to the level of EII(Man) activity.
authors.affiliation: EC Slater Institute, BioCentrum, University of Amsterdam, 1018 TV Amsterdam, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Chaillou
authors.forename: P H
authors.initials: PH
authors.lastname: Pouwels
authors.forename: P W
authors.initials: PW
authors.lastname: Postma
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001693:Biological Transport, Active / Q000502:physiology; D002250:Carbon Radioisotopes / Q000493:pharmacokinetics; D004058:Diffusion; D005816:Genetic Complementation Test; D007700:Kinetics; D007780:Lacticaseibacillus casei / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D008358:Mannose / Q000378:metabolism*; D009154:Mutation; D010728:Phosphoenolpyruvate / Q000378:metabolism*; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism / Q000502:physiology*; D010957:Plasmids; D013045:Species Specificity; D014170:Transformation, Genetic; D014994:Xylose / Q000493:pharmacokinetics*
chemical_list: D002250:Carbon Radioisotopes; D010728:Phosphoenolpyruvate; D000255:Adenosine Triphosphate; D014994:Xylose; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C037992:phosphoenolpyruvate-mannose phosphotransferase; D008358:Mannose