Schematic representation of the slg gene clusters of the two model bacteria G. stearothermophilus NRS 2004/3a and P. alvei CCM2051T. Individual stages of the S-layer glycosylation process are colour coded as follows: blue, monosaccharide biosynthesis; red, glycan assembly; orange, glycan transfer; green, export; grey, transposase; black, unknown function; yellow, S-layer protein. The corresponding percentage G+C base composition is given below each slg gene cluster map. Designation of ORFs in alphabetical order is as follows: rmlA, glucose-1-phosphate thymidylyltransferase; rmlB, dTDP-D-glucose 4,6-dehydratase; rmlC, dTDP-dehydrorhamnose 3,5-epimerase; rmlD, dTDP-dehydrorhamnose reductase; sgsE, S-layer protein precursor of G. stearothermophilus NRS 2004/3a; spaA, S-layer protein precursor of P. alvei CCM 2051T; tagD, putative glycerol-3-phosphate cytidyltransferase; wsaA, TPR-repeat containing protein; wsaB, putative oligosaccharyl:protein transferase; wsaC, α1,3-rhamnosyltransferase; wsaD,
α1,3-rhamnosyltransferase; wsaE, α1,2-rhamnosyltransferase, α1,3-rhamnosyltransferase, 2-O-methyltransferase; wsaF, β1,2-rhamnosyltransferase; wsaP, UDP-Gal:phosphoryl-polyprenol Gal-1-phosphate transferase; wsfA, asparagine synthase homologue; wsfC, putative CDP-glycerol:poly(glycerophosphate) glycerophosphotransferase, putative β1,4-galactosyltransferase, putative β1,3-N-acetylmannosamine transferase; wsfD, putative α1,6-glucosyltransferase; wsfE, putative β1,4-N-acetylmannosamine transferase; wsfF, putative α1,3-rhamnosyltransferase; wsfG, putative α1,3-rhamnosyltransferase; wsfH, putative UDP-Glc:phosphoryl-polyprenol Glc-1-phosphate transferase; wsfP, UDP-Gal:phosphoryl-polyprenol Gal-1-phosphate transferase; wzm, ABC transporter integral membrane protein; wzt, ABC transporter nucleotide-binding protein.