Glucose Metabolism in Xanthomonas campestris

Abstract

The pathways of glucose metabolism in Xanthomonas campestris closely resemble those described for Pseudomonas aeruginosa, in which two discrete systems exist for the uptake of glucose, one periplasmic and oxidative requiring glucose dehydrogenase activity, the second intracellular and phosphorylative. These systems lead to the production of 6-phosphogluconate, which may be metabolized via the Entner-Doudoroff pathway and the pentose phosphate pathway. Terminal oxidation is mediated by the tricarboxylic acid cycle. A mucoid strain of X. campestris lacked glucose dehydrogenase activity and thus the oxidative pathway was not functional; the pentose phosphate pathway was also inoperative in this strain, as evidenced by the absence of 6-phosphogluconate dehydrogenase activity. Nonmucoid mutants appeared identical to the parent strain; however, a second group of mutants (crenated mutants) were derepressed for both glucose dehydrogenase and 6-phosphogluconate dehydrogenase. Gluconate kinase was not detected in any of the X. campestris strains studied when grown on glucose; however, growth of the parent strain on gluconate resulted in the induction of this enzyme.