Glucose-6-phosphate dehydrogenase deficiency in pleiotropic carbohydrate-negative mutant strains of Rhizobium meliloti

Abstract

Several mutant strains of Rhizobium meliloti isolated after nitrosoguanidine mutagenesis were selected as unable to grow on mannose. Some of them also failed to grow on glucose, fructose, ribose, and xylose but grew on L-arabinose, galactose, and many other carbon sources. Biochemical analysis demonstrated that the mutants lacked NAD-and NADP-linked glucose-6-phosphate dehydrogenase activities that reside on a single enzyme species. One such mutant was found to accumulate glucose-6-phosphate, and this could partially explain the inhibition of growth observed on mixtures of permissive and nonpermissive carbon sources. Symbiotic properties remained unaffected in all these mutants.

Glucose 6-phosphate dehydrogenase is required for sucrose and trehalose to be efficient osmoprotectants inSinorhizobium meliloti

“…No significant differences were observed between the dry weights of plant shoots inoculated with mutant or wild‐type strains (data not shown). This result obtained with the 102F34 SmR strain lacking G6PD activity is consistent with the plant phenotype of a zwf mutant of S. meliloti strain L5‐30 previously described by Cervenansky and Arias [16].…”

“…Previously [16] it was shown that a zwf mutation blocks the ability of S. meliloti L5‐30 to grow on glucose, fructose, ribose and xylose as single carbon sources, and that the addition of these sugars during growth on permissive carbon sources caused growth inhibition, which was most likely due to the accumulation of glucose 6‐phosphate. This latter is well known for its inhibitory effect on cell growth.…”

The Entner-Doudoroff pathway: history, physiology and molecular biology

“…In Alcaligenes eutrophus, phosphoglycerate mutase mutants lose the ability to grow on succinate, but are still able to grow on fructose, a pattern similar to that observed for Pseudomonas mutants of the triose phosphate pathway [62]. Mutants of Rhizobium meliloti that are defective in glucose-6-phosphate dehydrogenase activity are impaired for growth on several carbohydrates and accumulate significant quantities of glucose-6-phosphate from galactose, despite almost normal growth on that sugar [63]. One common feature of each of the organisms mentioned above is that they do not utilize the Embden-Meyerhof-Parnas pathway, due to deficiency of 6-phosphofructokinase.…”

Study of a fructose-negative mutant of Rhizobium meliloti

“…Indeed, Bi3ck and Neidhart [23] and Fraenkel [24] previously suggested that inhibition of growth by sugars whose metabolism is blocked is due to the intracellular accumulation of metabolites at the block. Also, Cervenansky and Arias [5] and Arias et aL [3] showed inhibition of growth when cells of phosphoglucose dehydrogenase and phosphoglucose isomerase mutants of R. meliloti were grown in the presence of permissive and non-permissive substrates. This inhibition was associated respectively with the accumulation of G-6-P and F-6-P.…”

“…whereas sucrose, fructose, glucose and other hexoses were not oxidized [2]. Mutants of R. meliloti impaired in specific sugar catabolic pathways gave generally effective nodules [3][4][5][6][7]. However, mutants defective in transport or metabolism of tricarboxylic acid cycle intermediates were unable to fix nitrogen [8][9][10].…”