A deeper investigation on carbohydrate cycling in Sinorhizobium meliloti

Recycling of triose-phosphate and pentose-phosphate was previously reported on glucose in Sinorhizobium meliloti, a polysaccharide-synthesizing bacterium, but the metabolic basis of such processes remained unclear. In this work, we have used (13)C-labelling strategies to demonstrate that carbohydrate cycling in this organism is independent of the gluconate bypass, the alternative pathway for glucose assimilation involving its periplasmic oxidation into gluconate. Furthermore, carbohydrate cycling in S. meliloti is also observed on fructose, making the situation in this bacterium significantly different from that depicted for alginate-synthesizing species.