中文摘要：

讨论了一类具有质体非均匀恒化器模型的平衡态解，首先利用上下解方法与极值原理得到恒化器模型的先验估计；然后利用不动点指标理论讨论恒化器模型正解的共存性，并且得到了正解存在的充分条件．

英文摘要：

In this paper, a competition model between plasmid-bearing and plasmid-free organisms in the unstirred chemostat is researched. Firstly, a priori estimation is obtained by use of upper and lower solution method and the maximum principle. Secondly, the sufficient condition of existence on the coexistence solutions are proved by applying fixed-point index theory.