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Applied and Environmental Microbiology, September 2000, p. 3807-3813, Vol. 66, No. 9
National Livestock Research Institute, Rural
Development Administration, Suweon 441-350,1 and
School of Agricultural Biotechnology, Seoul National
University, Suweon 441-744,2 Korea, and
Institute of BioAgricultural Resources, Academia Sinica,
Taipei 115, Taiwan, Republic of China3
Received 4 February 2000/Accepted 21 June 2000
To assess the relative contributions of microbial groups (bacteria,
protozoa, and fungi) in rumen fluids to the overall process of plant
cell wall digestion in the rumen, representatives of these groups were
selected by physical and chemical treatments of whole rumen fluid and
used to construct an artificial rumen ecosystem. Physical treatments
involved homogenization, centrifugation, filtration, and heat
sterilization. Chemical treatments involved the addition of antibiotics
and various chemicals to rumen fluid. To evaluate the potential
activity and relative contribution to degradation of cell walls by
specific microbial groups, the following fractions were prepared: a
positive system (whole ruminal fluid), a bacterial (B) system, a
protozoal (P) system, a fungal (F) system, and a negative system
(cell-free rumen fluid). To assess the interactions between specific
microbial fractions, mixed cultures (B+P, B+F, and P+F systems) were
also assigned. Patterns of degradation due to the various treatments
resulted in three distinct groups of data based on the degradation rate
of cell wall material and on cell wall-degrading enzyme activities. The
order of degradation was as follows: positive and F systems > B
system > negative and P systems. Therefore, fungal activity was
responsible for most of the cell wall degradation. Cell wall
degradation by the anaerobic bacterial fraction was significantly less
than by the fungal fraction, and the protozoal fraction failed to grow
under the conditions used. In general, in the mixed culture systems the
coculture systems demonstrated a decrease in cellulolysis compared with
that of the monoculture systems. When one microbial fraction was
associated with another microbial fraction, two types of results were
obtained. The protozoal fraction inhibited cellulolysis of cell wall
material by both the bacterial and the fungal fractions, while in the
coculture between the bacterial fraction and the fungal fraction a
synergistic interaction was detected.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Relative Contributions of Bacteria, Protozoa, and
Fungi to In Vitro Degradation of Orchard Grass Cell Walls and
Their Interactions
*
Corresponding author. Mailing address: School of
Agricultural Biotechnology, Seoul National University, Suweon 441-744, Korea. Phone: 82-31-290-2348. Fax: 82-31-295-7875. E-mail:
jongha{at}snu.ac.kr.
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