Danso S K, Alexander M
Appl Microbiol. 1975 Apr;29(4):515-21. doi: 10.1128/am.29.4.515-521.1975.
Tetramitus rostratus and strains of Hartmanella, Naegleria, and Vahlkampfia consumed large numbers of Rhizobium meliloti cells in a salt solution, but protozoan multiplication and the bacterial decline stopped when the prey density fell to about 10-6 to 10-7 cells/ml. At higher prey densities, the maximum numbers of Hartmanella sp. and Naegleria sp. were proportional to the quantity of R. meliloti initially provided to the amoebas. When supplemental rhizobia were supplied to Hartmanella sp. or Naegleria sp. after their active feeding had terminated, presumably because the remaining 10-6 or 10-7 bacteria/ml could not be captured, replication of the protozoa was initiated. The rate of elimination of rhizobia present in large populations was proportional to the initial abundance of Naegleria sp., but the final numbers of amoebas and surviving R. meliloti cells were independent of initial numbers of predators. The surviving bacteria were not intrinsically resistant to attack because 98% of the survivors, when concentrated, were consumed. It is suggested that large populations of bacteria in nature may be reduced in size by predatory protozoa, but many of the prey cells will not be eliminated.
有喙四膜虫以及哈特曼氏阿米巴、耐格里属阿米巴和瓦氏阿米巴的菌株在盐溶液中消耗了大量的苜蓿根瘤菌细胞，但当猎物密度降至约10⁻⁶至10⁻⁷个细胞/毫升时，原生动物的繁殖和细菌数量的下降停止。在较高的猎物密度下，哈特曼氏阿米巴属和耐格里属阿米巴的最大数量与最初提供给变形虫的苜蓿根瘤菌数量成正比。当哈特曼氏阿米巴属或耐格里属阿米巴在其活跃摄食结束后（推测是因为剩余的每毫升10⁻⁶或10⁻⁷个细菌无法被捕食）补充根瘤菌时，原生动物的复制开始。大量存在的根瘤菌的消除速率与耐格里属阿米巴的初始丰度成正比，但变形虫和存活的苜蓿根瘤菌细胞的最终数量与捕食者的初始数量无关。存活的细菌并非天生具有抗攻击能力，因为当将98%的幸存者浓缩时，它们会被消耗掉。这表明自然界中大量的细菌可能会被捕食性原生动物减少数量，但许多猎物细胞不会被消灭。
