Gut microbiota selects fungi Fungi, such as Candida albicans , are found in the mammalian gut, but we know little about what they are doing there. Tso et al. put C. albicans under evolutionary pressure by serial passage in mice that were treated with antibiotics and were thus lacking gut bacteria (see the Perspective by d'Enfert). Passage accelerated fungal mutation, especially around the FLO8 gene, resulting in low-virulence phenotypes unable to form hyphae. Nevertheless, these phenotypes stimulated proinflammatory cytokines and conferred transient cross-protection against several other gut inhabitants. However, if an intact microbiota was present, only the virulent hyphal forms persisted. Science , this issue p. 589 ; see also p. 523