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This suggests that some change occurs in the bacterial community, in the absence of B. cellulosilyticus, that enables arabinose from pea fibre to be degraded as much as it would be if all 15 bacterial strains were present.

When both B. ovatus and B. cellulosilyticus were absent from the bacterial populations, arabinoxylan-coated beads retained their original levels of arabinose, revealing that none of the remaining 13 bacterial strains took advantage of arabinoxylan availability.

When mice that had been colonized only with B. cellulosilyticus or Bacteroides vulgatus were given food particles coated with pea fibre, the levels of arabinose in the recovered beads were lower than the original levels, demonstrating that both of these bacterial species had metabolized this molecule in vivo.

The level of degradation of arabinose in the arabinan-rich pea-fibre beads was then compared, and was found to be the same in both cases.

Both approaches pointed to a gene for an enzyme that makes arabinose, a sugar found primarily in the plant cell wall, Willis reported.