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Factors Affecting the Antibacterial Activity of the Ruminal Bacterium,Streptococcus bovis HC5
Authors:Mantovani  Hilário C  Russell  James B
Institution:(1) Section of Microbiology, Cornell University, Wing Hall, Ithaca, NY 14853, USA, US;(2) Agricultural Research Service, USDA, Ithaca, NY 14853, USA, US
Abstract:Streptococcus bovis HC5 inhibits a variety of S. bovis strains and other Gram-positive bacteria, but factors affecting this activity had not been defined. Batch culture studies indicated that S. bovis HC5 did not inhibit S. bovis JB1 (a non-bacteriocin-producing strain) until glucose was depleted and cells were entering stationary phase, but slow-dilution-rate, continuous cultures (0.2 h−1) had as much antibacterial activity as stationary-phase batch cultures. Because the activity of continuous cultures (0.2–1.2 h−1) was inversely related to the glucose consumption rate, it appeared that the antibacterial activity was being catabolite repressed by glucose. When the pH of continuous cultures (0.2 h−1) was decreased from 6.7 to 5.4, antibacterial activity doubled, but this activity declined at pH values less than 5.0. Continuous cultures (0.2 h−1) that had only ammonia as a nitrogen source had antibacterial activity, and large amounts of Trypticase (10 mg ml−1) caused only a 2.0-fold decline in the amount of HC5 cell-associated protein that was needed to prevent S. bovis JB1 growth. Because S. bovis HC5 was able to produce antibacterial activity over a wide range of culture conditions, there is an increased likelihood that this activity could have commercial application. Received: 6 February 2002 / Accepted: 27 March 2002
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