Ciliated protozoa (ciliates) play vital roles in biological wastewater-treatment processes, however, combined effects of abiotic and biotic factors as well as the importance of species-specificity of bacterial food organisms on population growth dynamics remain poorly understood, which are hampering the management and optimization of biological wastewater treatment processes. This study investigated the effects of food resources and ammonium nitrogen (NH₄⁺) exposure, both independently and in combination, on the population growth of the bacterivorous ciliate Paramecium caudatum. Results showed that, when fed with two different bacterial food organisms, population growth performance of P. caudatum differed significantly and increased with the addition of protozoa pellet medium. When exposed to NH₄⁺ population growth declined and metabolic enzyme activities were altered. The negative effects of NH₄⁺ on population growth could be weakened by supplementing the food resource with protozoa pellet media. In brief, it was confirmed that the existence of interactive effect of food resources and ammonium nitrogen, as well as the importance of species-specificity of bacterial food organisms on the population growth performance of ciliates. These findings might lead to the development of a valuable strategy for improving the performance of biological wastewater-treatment processes.

纤毛虫（纤毛虫）在生物废水处理过程中起着至关重要的作用，然而，非生物和生物因素的共同作用以及细菌性食物生物的物种特异性对种群增长动态的重要性仍然知之甚少，这阻碍了管理和优化生物废水处理工艺。这项研究调查了食物资源和铵态氮（NH ₄ ⁺）暴露对细菌性纤毛虫尾草履虫种群增长的影响，无论是单独还是结合使用。结果表明，当饲喂两种不同的细菌性食物生物时，尾孢假单胞菌的种群生长性能差异显着，并随着原生动物颗粒培养基的添加而增加。当暴露于NH ₄ ^+时，种群增长下降，代谢酶活性改变。可以通过用原生动物颗粒培养基补充食物资源来减弱NH ₄ ⁺对人口增长的负面影响。简而言之，证实了食物资源和铵态氮相互作用的影响，以及细菌性食物生物的物种特异性对纤毛虫种群生长性能的重要性。这些发现可能会导致开发一种提高生物废水处理工艺性能的有价值的策略。