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Appl Environ Microbiol, May 1998, p. 1796-1804, Vol. 64, No. 5
AgResearch, Grasslands Research Centre,
Palmerston North, New Zealand,1 and
Animal Research Institute,
Received 23 September 1997/Accepted 20 February 1998
Pasture-grazed dairy cows, deer, and sheep were tested for the
presence of ammonia-hyperproducing (HAP) bacteria in roll tubes containing a medium in which tryptone and Casamino Acids were the sole
nitrogen and energy sources. Colonies able to grow on this medium
represented 5.2, 1.3, and 11.6% of the total bacterial counts of dairy
cows, deer, and sheep, respectively. A total of 14 morphologically
distinct colonies were purified and studied further. Restriction
fragment length polymorphisms of 16S rRNA genes indicated that all
isolates differed from the previously described HAP bacteria,
Clostridium aminophilum, Clostridium
sticklandii, and Peptostreptococcus anaerobius.
Carbon source utilization experiments showed that five isolates (C2,
D1, D4, D5, and S1) were unable to use any, or very few, of the carbon
sources tested. Biochemical tests and phylogenetic analyses of 16S
ribosomal DNA sequences indicated that all isolates were monensin
sensitive; that D1 and S1 belonged to the genus
Peptostreptococcus, that D4 and D5 belonged to the family
Bacteroidaceae, where D4 was similar to Fusobacterium necrophorum; and that C2 was most similar to an unidentified
species from the genus Eubacterium. Growth on liquid medium
containing tryptone and Casamino Acids as the sole nitrogen and energy
source showed that D1, D4, and S1 grew rapidly (specific growth rates of 0.40, 0.35, and 0.29 h
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Ammonia-Hyperproducing Bacteria from New
Zealand Ruminants
1, respectively), while C2 and
D5 were slow growers (0.25 and 0.10 h
1, respectively).
Ammonia production rates were highest in D1 and D4, which produced
945.5 and 748.3 nmol/min per mg of protein, respectively. Tests of
individual nitrogen sources indicated that D1 and D4 grew best on
tryptone, S1 grew equally well on Casamino Acids or tryptone, and C2
and D5 grew poorly on all nitrogen sources. The intact proteins casein
and gelatin did not support significant growth of any of the isolates.
These isolates extend the diversity of known HAP rumen bacteria and
indicate the presence of significant HAP bacterial populations in
pasture-grazed New Zealand ruminants.
*
Corresponding author. Mailing address: AgResearch,
Grasslands Research Centre, Tennent Dr., Private Bag 11008, Palmerston North, New Zealand. Phone: 64 6 356 8019. Fax: 64 6 351 8003. E-mail:
attwoodg{at}agresearch.cri.nz.
Appl Environ Microbiol, May 1998, p. 1796-1804, Vol. 64, No. 5
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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