Patients with inflammatory bowel disease (IBD) are particularly susceptible to behavioral diagnoses, and the microbiome has been repeatedly implicated in the pathogenesis of IBD. The intestinal microbiome’s ability to affect behavior has become increasingly recognized and studied. The so-called ‘psychobiome’ has been linked to a plethora of neurological and psychological diagnoses, including autism and Parkinson’s disease. Despite the ability of many bacterial species within the human intestinal microbiome to synthesize neurotransmitters, it has never been previously reported that a single bacterial species is sufficient to induce depression. Here, we demonstrate that our mouse model of Crohn’s disease (CD)-like ileitis, the SAMP1/YitFc (SAMP1), does not exhibit baseline behavioral abnormalities. By comparison, SAMP6 mice develop depressive-like behavior that is associated with a rise in the GABA-producing bacterial genus Parabacteroides. We finally demonstrate that administration of Parabacteroides distasonis into our SAMP1 mice induces depressive-like behavior. Colonization with P. distasonis was not associated with increased intestinal inflammation or alterations in other measures of behavior. The intestinal environment of CD may be particularly conducive to colonization with P. distasonis and subsequent induction of depressive-like behavior. To our knowledge, this is the first report of a bacterial species specifically inducing depressive-like behavior.

炎症性肠病 (IBD) 患者特别容易受到行为诊断的影响，并且微生物群一再与 IBD 的发病机制有关。肠道微生物组影响行为的能力已得到越来越多的认识和研究。所谓的“心理生物组”与大量的神经和心理诊断有关，包括自闭症和帕金森病。尽管人类肠道微生物组中的许多细菌物种具有合成神经递质的能力，但以前从未有报道称单一细菌物种足以诱发抑郁症。在这里，我们证明我们的克罗恩病 (CD) 样回肠炎小鼠模型 SAMP1/YitFc (SAMP1) 没有表现出基线行为异常。通过比较，副杆菌。我们最终证明，将Parabacteroides distasonis 施用到我们的 SAMP1 小鼠中会诱导抑郁样行为。P. distasonis的定植与肠道炎症增加或其他行为指标的改变无关。CD 的肠道环境可能特别有利于P. distasonis的定植和随后的抑郁样行为的诱导。据我们所知，这是第一份关于特异性诱导抑郁样行为的细菌物种的报告。