Cellobiose uptake and metabolism by Ruminococcus flavefaciens |
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Authors: | C T Helaszek B A White |
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Institution: | Department of Animal Sciences, University of Illinois, Urbana-Champaign 61801. |
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Abstract: | The cellulolytic ruminal bacterium Ruminococcus flavefaciens FD-1 utilizes cellobiose but not glucose as a substrate for growth. Cellobiose uptake by R. flavefaciens FD-1 was measured under anaerobic conditions (N2), using G-3H]cellobiose. The rate of cellobiose uptake for early- or late-log-phase cellobiose-grown cells was 9 nmol/min per mg of whole-cell protein. Cellobiose uptake was inhibited by electron transport inhibitors, iron-reactive compounds, proton ionophores, sulfhydryl inhibitors, N,N-dicyclohexylcarbodiimide, and NaF, as well as lasalocid and monensin. The results support the existence of an active transport system for cellobiose. Transport of U-14C]glucose was not detected with this system. Phosphorylation of cellobiose was not by a phosphoenolpyruvate-dependent system. Cellobiose phosphorylase activity was detected by both a coupled spectrophotometric assay and a discontinuous assay. The enzyme was produced constitutively in cellobiose-grown cells at a specific activity of 329 nmol/min per mg of cell-free extract protein. |
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