Microbiome composition has a pivotal role in neurobehavioral development. However, there is limited information about the role of the microbiome in sociability of mice in complex social contexts. Germ-free (GF) mice were reared in a microbiota-free environment until postnatal day 21 and then transferred to a room containing specific pathogen free (SPF) mice. At 9 weeks old, group social behaviors were measured for three GF mice and three SPF mice unfamiliar to each other. GF mice spent less time in the center area of the arena and there were longer inter-individual distances compared with SPF mice. GF mice also had decreased brain-derived neurotrophic factor (BDNF) and increased ΔFosB mRNA in the prefrontal cortex compared to SPF mice. There were differences in the gut microbiome composition between GF and SPF mice; however, if cohabitating after weaning, then their microbiome composition became equivalent and group differences in behavior and BDNF and ΔFosB mRNA expression disappeared. These results demonstrate that the bacterial community can modulate neural systems that are involved in sociability and anxiety during the developmental period and suggest that sociability and anxiety can be shaped depending on the microbiome environment through interaction with conspecifics.

微生物组组成在神经行为发育中具有关键作用。然而，关于微生物组在复杂社会环境中对小鼠社交能力的作用的信息有限。无菌 (GF) 小鼠在无微生物环境中饲养，直到出生后第 21 天，然后转移到含有特定无病原体 (SPF) 小鼠的房间。在 9 周大时，测量了三只彼此不熟悉的 GF 小鼠和三只 SPF 小鼠的群体社交行为。与 SPF 小鼠相比，GF 小鼠在竞技场中心区域停留的时间更少，个体间距离更长。与 SPF 小鼠相比，GF 小鼠的前额叶皮层中的脑源性神经营养因子 (BDNF) 也减少了，ΔFosB mRNA 增加了。GF 和 SPF 小鼠的肠道微生物组组成存在差异；然而，如果断奶后同居，则它们的微生物组组成变得相同，行为和 BDNF 和 ΔFosB mRNA 表达的组差异消失。这些结果表明，细菌群落可以调节发育期间参与社交和焦虑的神经系统，并表明社交和焦虑可以根据微生物群环境通过与同种细菌的相互作用而形成。