Although gut microbiota profiles differ remarkably between healthy individuals, several features have been suggested to define a “healthy gut microbiome”. First of all, our gut microbiota can be understood, in many cases, to be redundant given that many bacterial species have similar functions. Furthermore, a healthy gut microbiome is temporally stable and resistant to perturbations and, over time, is more similar to itself than to that of another healthy person. Finally, a healthy gut microbiome is resilient, which means that it returns to a healthy state after a perturbation. For example, after antibiotic treatment, our gut microbiota usually recovers to its previous state a few weeks or months later. As such, a plausible definition of microbial health does not comprise a single static state, but rather a dynamic equilibrium. Meanwhile, when a perturbation stimulus becomes chronic and leads to an altered stable gut microbiome that causes harm to the host, this is called dysbiosis. Also see the following for detailed discussion of microbiome as emerging biomarker of health. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3577372/