Fig. 3

Genetic organization of HePS biosynthesis encoding gum-like clusters. The gum-like clusters of K. baliensis strains DSM 14400 + NBRC 16680 are depicted in (a). The cluster has an overall size of ~25 kb and involves 19 genes, including glycosyltransferases (gt), hypothetical proteins (hp), and eight gum like genes (gumB, -C, -D, -E, -H, -J, -K, and –M), which are marked in grey. Furthermore, the cluster contains a putative endoglucanase (e.g.), oxidoreductase (ox) and a UDP-glucose dehydrogenase (ugd). b, c show the related gum like clusters of the AAB strains Ga. diazotrophicus PAI5 and Komagataeibacter xylinus E25. The Ga. diazotrophicus cluster exhibits, in comparison to both K. baliensis clusters, an additional gumF gene, that could putatively incorporate acetyl-residues at specific positions into the related HePS. The so called acetan cluster of Ko. xylinus harbors—besides an additional gumF gene—a rhamnosyl transferase, coded by aceR, as well as a mannose-phosphate-guanyltransferase (mpg). The nomenclature for the acetan cluster in (c) is based on Griffin AM, Morris VJ and Gasson MJ [44], while brackets under the particular genes mark the homologous gum genes. In (d) the gum cluster of X. campestris, which consists of gumB, -C, -D, -E, -F, -G, -H, -I, -J, -K, -L, -M, -N and –P, is depicted. The dotted squares in the particular gum-clusters of B, C and D mark genes, which alter between the specific clusters (relative to both K. baliensis gum-like clusters). The corresponding monomer compositions of the respective HePSs are shown at the right. The putative functions of the corresponding annotated genes are as follows (derived from Pühler et al. [26] and Griffin et al. [45]): aceA UDP-glucosyltransferase, aceC GDP-mannosyltransferase, aceP glucosyltransferase, aceQ glucosyltransferase, aceR rhamnosyltransferase, gumJ export protein, gumE polymerization or export protein, gumK catalyzes the addition of glucuronic acid, gumD catalyzes the addition of glucose-1-phosphate, gumM catalyzes the addition of glucose in β-1,4-position, gumC polymerization and export protein, gumG acetyl transferase, gumL pyruvyl transferase, gumH catalyzes the addition of internal mannose, gumI β-mannosyltransferase, gumB polymerization and export protein, RE dTDP-4-dehydrorhamnose 3,5-epimerase, manB Mannose-1-phosphate guanylyltransferase, tp transporter