Carbohydrate metabolism inFibrobacter succinogenes: What NMR tells us

Abstract

Fibrobacter succinogenes is a major rumen fibrolytic bacterium found in high numbers when ruminants are fed cellulose-rich diets. It produces a very efficient fibrolytic system comprising numerous enzymes, but the organization and catalytic features of this system remain unclear. We were using nuclear magnetic resonance (NMR) to study carbohydrate metabolism by Fibrobacter spp. well before the term 'metabolomics' was coined. We first analyzed in detail the NMR spectra arising from resting cells of F. succinogenes provided with glucose, cellobiose or cellulose as a substrate. We were able to show carbohydrate cycling and reversibility of some steps. The use of 1D and 2D 1 H and 13 C NMR showed the synthesis by the cells of unexpected oligosaccharides: maltodextrins, maltodextrin-1-phosphate, and other glucose derivatives. We also showed that maltodextrins and maltodextrins-1-phosphate were synthesized and excreted out of the cell, and could originate from exogenous sugars or endogenous glycogen. According to the substrate and the physiological state of the bacterium (resting or growing cells), metabolic deviations toward the synthesis of these oligosaccharides were observed. We have also used liquid-and solid-state NMR to monitor wheat straw degradation by F. succinogenes. The originality of this NMR approach was to investigate the activity of an entire fibrolytic system on an intact complex substrate (wheat straw). No preferential degradation of amorphous versus crystalline cellulose was observed, nor of cellulose versus hemicelluloses. We showed for the first time a sequential activity of some enzymes of F. succinogenes S85 on wheat straw. In conclusion, our studies illustrate the utility of various NMR approaches to study and better understand sugar and polysaccharide metabolism in rumen bacteria.

Diet-Dependent Modular Dynamic Interactions of the Equine Cecal Microbiota

“…However, F. succinogens is known to accumulate large amounts of glycogen, representing up to 60–70% of the dry cell mass (7). A possible explanation for this observation is that the accumulation and degradation of glycogen are separated in time.…”

Production of oligosaccharides and cellobionic acid by Fibrobacter succinogenes S85 growing on sugars, cellulose and wheat straw

“…In addition, the complete genome sequence of the strain S85 of F. succinogenes revealed more than 100 predicted enzymes active against plant polysaccharide (Qi et al 2005), suggesting a high potential hydrolytic activity of this organism. The sugar metabolism by F. succinogenes S85 was also extensively investigated (Forano et al 2008), while metabolisation of natural substrates was much less explored. In a previous work, we showed that resting cells of F. succinogenes S85 were able to synthesise and release oligosaccharides identified by 2D-NMR techniques as maltodextrins (MD), maltodextrin-1-phosphate (MD-1P) and another unknown phosphorylated sugar.…”

In Silico Comparison of the Hemicelluloses Xyloglucan and Glucuronoarabinoxylan in Protecting Cellulose from Degradation

“…For example, F. succinogenes appears to utilise glucose and cellobiose more readily than larger oligosaccharides [22], whereas the converse holds for some other microorganisms [23].…”