Stress has been shown to disturb the balance of human intestinal microbiota and subsequently causes mental health problems like anxiety and depression. Our previous study showed that ingesting the probiotic strain, Lactobacillus (L.) plantarum P-8, for 12 weeks could alleviate stress and anxiety of stressed adults. The current study was a follow-up work aiming to investigate the functional role of the gut metagenomes in the observed beneficial effects. The fecal metagenomes of the probiotic (n = 43) and placebo (n = 36) receivers were analyzed in depth. The gut microbiomes of the placebo group at weeks 0 and 12 showed a significantly greater Aitchison distance (P < 0.001) compared with the probiotic group. Meanwhile, the Shannon diversity index of the placebo group (P < 0.05) but not the probiotic group decreased significantly at week 12. Additionally, significantly more species-level genome bins (SGBs) of Bifidobacterium adolescentis, Bifidobacterium longum, and Fecalibacterium prausnitzii (P < 0.01) were identified in the fecal metagenomes of the probiotic group, while the abundances of SGBs representing the species Roseburia faecis and Fusicatenibacter saccharivorans decreased significantly (P < 0.05). Furthermore, the 12-week probiotic supplementation enhanced the diversity of neurotransmitter-synthesizing/consuming SGBs and the levels of some predicted microbial neuroactive metabolites (e.g., short-chain fatty acids, gamma-aminobutyric acid, arachidonic acid, and sphingomyelin). Our results showed a potential link between probiotic-induced gut microbiota modulation and stress/anxiety alleviation in stressed adults, supporting that the gut-brain axis was involved in relieving stress-related symptoms. The beneficial effect relied not only on microbial diversity changes but more importantly gut metagenome modulations at the SGB and functional gene levels.

压力已显示出会干扰人体肠道菌群的平衡，并随后导致精神健康问题，如焦虑和抑郁。我们以前的研究表明，摄取益生菌，乳杆菌（大号）植物P-8，12周可以减轻压力，并强调成人的焦虑。当前的研究是一项后续工作，旨在研究肠道元基因组在观察到的有益作用中的功能作用。深入分析了益生菌（n = 43）和安慰剂（n = 36）接受者的粪便基因组。安慰剂组在第0周和第12周的肠道微生物组的Aitchison距离（P <0.001）与益生菌组相比。同时，在安慰剂组的香农多样性指数（P  <0.05），但不益生菌组显著在第12周。另外，显著更多种级别的基因组仓（SGBS）的下降青春双歧杆菌，长双歧杆菌，和Fecalibacterium prausnitzii（P 在益生菌组的粪便基因组中鉴定到<0.01），而代表Fascis Roseburia faecis和fusicatenibacter saccharivorans物种的SGB的丰度显着下降（P <0.05）。此外，为期12周的益生菌补充提高了神经递质合成/消耗SGB的多样性以及某些预测的微生物神经活性代谢产物（例如短链脂肪酸，γ-氨基丁酸，花生四烯酸和鞘磷脂）的水平。我们的结果表明，在受压力的成年人中，益生菌诱导的肠道菌群调节与压力/焦虑缓解之间存在潜在的联系，这表明肠道脑轴参与了缓解压力相关症状的过程。有益效果不仅取决于微生物多样性的变化，而且更重要的是取决于SGB和功能基因水平的肠道元基因组调控。