微生物在宿主体内的持久存在通常并不是偶然的，而是反映了具有两种或更多不同生命形式的生物的同时出现。有这样一个假说：对微生物和宿主来说都存在一种选择，这种选择能使双方对于涉及寄生或共生的一种生活的适应性最大化，符合一种稳定的进化策略。Martin Blaser 和 Denise Kirschner进一步发展了这一假说。他们开发出一个平衡模型，该模型能够解释人体中微生物之间三种很不相同的互动类型的存在，它们分别涉及幽门螺杆菌（Helicobacter pylori）、伤寒沙门氏菌（Salmonella typhi）和结核分枝杆菌（Mycobacterium tuberculosis）。
原始出处:
Nature 449, 843-849 (18 October 2007) | doi:10.1038/nature06198
The equilibria that allow bacterial persistence in human hosts
Martin J. Blaser1 & Denise Kirschner2
We propose that microbes that have developed persistent relationships with human hosts have evolved cross-signalling mechanisms that permit homeostasis that conforms to Nash equilibria and, more specifically, to evolutionarily stable strategies. This implies that a group of highly diverse organisms has evolved within the changing contexts of variation in effective human population size and lifespan, shaping the equilibria achieved, and creating relationships resembling climax communities. We propose that such ecosystems contain nested communities in which equilibrium at one level contributes to homeostasis at another. The model can aid prediction of equilibrium states in the context of further change: widespread immunodeficiency, changing population densities, or extinctions.
Departments of Medicine and Microbiology, New York University School of Medicine, New York, New York 10016, USA
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
Correspondence to: Martin J. Blaser1 Correspondence should be addressed to M.B. (Email: martin.blaser@med.nyu.edu).
