Ref ID : 1176
M. Habte and M. Alexander; Protozoan density and the coexistence of protozoan predators and bacterial prey. Ecology 59(1):140-146, 1978
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Low numbers of Tetrahymena pyriformis provided with =2x10E9 Klebsiella pneumoniae or Rhizobium sp. cells/ml reduced the bacterial population only to 10E7/ml in solution. When 5-7x10E8 K. pneumoniae or 1x10E8 Rhizobium sp. were preyed the protozoan provided with 3x10E6 or 5x10E7 K. pneumoniae or 3-4x10E7 Rhizobium sp./ml reduced the prey population to 2-3x10E5/ml. However, when the initial number of T. pyriformis was high (2-34x10E4/ml) and the K. pneumoniae or Rhizobium sp. density was =10E7/ml, the animal did not reduce the bacterial population size. The data suggest that the number of K. pneumoniae or Rhizobium sp. cells able to coexist in solution with T. pyriformis was governed by the number of protozoa initially present or developing as a result of predation. By contrast, 10E5 Xanthomonas citri cells/ml coexisted with the ciliate whether this bacterium was provided at 7x10E6 or 8x10E8 cells/ml. In soil treated with 3.5x10E8 and 3.1x10E9 Rhizobium sp./g, the density of indigenous protozoa rose to 1-2x10E4 and 4-5x10E5/g, respectively, yet the density of rhizobial survivors stabilized at 3-7x10E7/g, a range higher than that observed in solution.