The K-type of each compared cluster is shown in red, followed by the strain/isolate identification and its NCBI accession number in parentheses. The blue segments connecting each cluster represent variably conserved PF-562271 (60–100% identity) regions among them (from a BLASTN comparison with e-value ≤ 10-4). Predicted glycosyltransferases are colored in orange, wzy and gnd homologs in yellow and purple, respectively. N.T., new K-type; N.D., K-type not determined. The cps Kp13 monosaccharide biosynthesis pathways: UDP-D-glucuronate, UDP-D-galacturonate and L-rhamnose As in other bacteria that produce group-1 capsules, galF delimits the 5’ region of cps Kp13. This gene

shows 100% identity to the galF sequence present in K. pneumoniae NK8

[GenBank:BAI43699], which codes for a UTP-glucose-1-phosphate uridylyltransferase (EC 2.7.7.9, Figure 3). This enzyme belongs to the nucleotidyltransferase family and catalyzes the reaction UTP + α-D-glucose 1-phosphate ↔ diphosphate + UDP-D-glucose. This enzyme is important because UDP-D-glucose serves as a precursor for the biosynthesis of bacterial lipopolysaccharides and capsular polysaccharides. It is also possible that the galF product interacts with the product of galU, thus elevating UDP-D-glucose concentration in the cell and providing more material for the synthesis of capsular polysaccharides [11]. In fact, a galU homolog found in Fluorouracil solubility dmso Kp13 outside the cps region (KP04702) shows 94% identity (BLASTP) to GalU from Shigella flexneri [Swiss-Prot:P0AEP6]. Immediately downstream of the rmlBADC operon, the gene ugd is found (Figure 1). It encodes a UDP-glucose 6-dehydrogenase (EC 1.1.1.22). As depicted in Figure 3, this enzyme converts UDP-D-glucose to UDP-D-glucuronate, a common constituent of bacterial capsules [7]. As with other sequences located in the 3’ region of the cps Kp13 gene cluster, this coding sequence exhibits remarkable amino acid conservation. It is 100% identical to Ugd from K. pneumoniae strains NK8 [GenBank:BAI43716] and Acesulfame Potassium VGH404 serotype K5 [GenBank:BAI43755] (Table 1), both studied by Shu et al. [15].

Uge catalyzes the conversion of UDP-D-glucuronate to UDP-D-galacturonate (Figure 3), which is also present in both bacterial capsules and LPS. In fact, Kp13 has two copies of this gene, uge-1 (KP03793) and uge-2 (KP03786). A NAD-dependent epimerase domain (Pfam accession no. PF01370) is predicted to occupy amino acids 4 to 230 in both Uge sequences. Two copies of uge are also found in the genome of K. pneumoniae subsp. rhinoscleromatis (which produces a K3 capsule), one in the cps cluster and an inverted adjacent copy in the cluster for LPS synthesis [16]. As the K3 CPS contains D-galacturonate in its composition, uge was considered the last gene of its cps cluster [16] instead of ugd as usually regarded [15, 17].