Competition for cellobiose among three predominant ruminal cellulolytic bacteria under substrate-excess and substrate-limited conditions

Article Abstract:

The ruminal cellulolytic bacteria Ruminococcus flavefaciens and Fibrobacter succinogens coexist in substrate-excess culture with almost equal population size. However, R. flavefaciens outcompetes the other strain for cellobiose in the substrate-limited condition, regardless of whether they are coinoculated or a steady-state culture of F. succinogens is challenged by R. flavefaciens. R. albus outcompetes F. succinogens and R. flavefaciens in substrate-excess and -limited conditions respectively. This is due to the selection in the chemostat of a population of R. albus with a higher affinity for cellobiose.

Analysis, Microbiology, Plant growing media, Competition (Biology), Ruminants

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Expression of 17 genes in Clostridium thermocellum ATCC 27405 during fermentation of cellulose or cellobiose in continuous culture

Article Abstract:

Expression of 17 genes associated with cellulose degradation, intracellular phosphorolysis, primary catabolism and catabolic regulation in Clostridium thermocellum ATCC 27405 grown at different rates was quantified to determine relative expression. It suggest that at least some cellulosomal components are transcriptionally regulated but differences in expression with growth rate or among substrates do not directly account for observed changes in fermentation end product distribution.

Clostridium, Bacterial genetics

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Studies of the extracellular glycocalyx of the anaerobic cellulolytic bacterium Ruminococcus albus 7

Article Abstract:

Variable-pressure scanning electron microscopy (VP-SEM) and chemical analysis were employed to characterize the glycocalyx of the ruminal bacterium Ruminococcus albus strain 7. The results have shown that the energy demand for synthesis of the nonprotein fraction of extracellular polymeric substances (EPS) by this organism has represented only a small fraction of the anabolic ATP expenditure of the bacterium.

South Africa, Microbial metabolism, Rumen fermentation, Glycocalyx

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