Production of maltodextrin 1-Phosphate byFibrobacter succinogenesS85

α-Glucan biosynthesis and the GlgE pathway in Mycobacterium tuberculosis

It has long been reported that Mycobacterium tuberculosis is capable of synthesizing the α-glucan glycogen. However, what makes this bacterium stand out is that it coats itself in a capsule that mainly consists of a glycogen-like α-glucan. This polymer helps the pathogen evade immune responses. In 2010, the biosynthesis of α-glucans has been shown to not only involve the classical enzymes of glycogen metabolism but also a distinct GlgE pathway. Since then, this pathway has attracted attention not least in terms of the quest for new inhibitors that could be developed into new treatments for tuberculosis. Some lines of recent inquiry have shed a lot of light on to how GlgE catalyses the polymerization of α-glucan, using α-maltose 1-phosphate (M1P) as a building block and how the pathways are regulated. Nevertheless, many unanswered questions remain regarding the synthesis and role of α-glucans in mycobacteria and the numerous other bacteria that possess the GlgE pathway.

Oligosaccharide synthesis in Fibrobacter succinogenes S85 and its modulation by the substrate

In this article we compared the metabolism of phosphorylated and unphosphorylated oligosaccharides (cellodextrins and maltodextrins) in Fibrobacter succinogenes S85 resting cells incubated with the following substrates: glucose; cellobiose; a mixture of glucose and cellobiose; and cellulose. Intracellular and extracellular media were analysed by (1)H-NMR and by TLC. The first important finding is that no cellodextrins were found to accumulate in the extracellular media of cells, regardless of the substrate; this contrasts to what is generally reported in the literature. The second finding of this work is that maltodextrins of degree of polymerization > 2 are synthesized regardless of the substrate, and can be used by the bacteria. Maltotriose plays a key role in this metabolism of maltodextrin. Maltodextrin-1-phosphate was detected in all the incubations, and a new metabolite, corresponding to a phosphorylated glucose derivative, was produced in the extracellular medium when cells were incubated with cellulose. The accumulation of these phosphorylated sugars increased with the degree of polymerization of the substrate.