Summary The intestinal microbiota influence neurodevelopment, modulate behavior, and contribute to neurological disorders. However, a functional link between gut bacteria and neurodegenerative diseases remains unexplored. Synucleinopathies are characterized by aggregation of the protein α-synuclein (αSyn), often resulting in motor dysfunction as exemplified by Parkinson's disease (PD). Using mice that overexpress αSyn, we report herein that gut microbiota are required for motor deficits, microglia activation, and αSyn pathology. Antibiotic treatment ameliorates, while microbial re-colonization promotes, pathophysiology in adult animals, suggesting postnatal signaling between the gut and the brain modulates disease. Indeed, oral administration of specific microbial metabolites to germ-free mice promotes neuroinflammation and motor symptoms. Remarkably, colonization of αSyn-overexpressing mice with microbiota from PD patients enhances physical impairments compared to microbiota transplants from healthy human donors. These findings reveal that gut bacteria regulate movement disorders in mice, and suggest that alterations in the human microbiome represent a risk factor for PD.

SUMMARY The gastrointestinal (GI) tract contains much of the body’s serotonin (5-hydroxytryptamine, 5-HT), but mechanisms controlling the metabolism of gut-derived 5-HT remain unclear. Here we demonstrate that the microbiota plays a critical role in regulating host 5-HT. Indigenous spore-forming bacteria (Sp) from the mouse and human microbiota promote 5-HT biosynthesis from colonic enterochromaffin cells (ECs), which supply 5-HT to the mucosa, lumen and circulating platelets. Importantly, microbiota-dependent effects on gut 5-HT significantly impact host physiology, modulating GI motility and platelet function. We identify select fecal metabolites that are increased by Sp and that elevate 5-HT in chromaffin cell cultures, suggesting direct metabolic signaling of gut microbes to ECs. Furthermore, elevating luminal concentrations of particular microbial metabolites increases colonic and blood 5-HT in germ-free mice. Altogether, these findings demonstrate that Sp are important modulators of host 5-HT, and further highlight a key role for host-microbiota interactions in regulating fundamental 5-HT-related biological processes.

Cell 161, 264-276; April 9, 2015) In Figure S5D of this article, the representative flow cytometry plot of forward versus side scatter for unstimulated platelets was incorrectly duplicated during the final formatting of the paper for SPF+PCPA and GF conditions. The figure has been corrected online, and the originally published descriptions of the results in the text and figure legend are accurate.In Figure 3A, the ''GF+conv'' bar represents germ-free (GF) mice conventionalized with standard pathogen-free (SPF) microbiota on postnatal day 21 (P21). The published main text incorrectly referred to conventionalization on P42. Though we show in Figure 1B very similar levels of colonic serotonin after conventionalization on P21 versus P42, the ''GF+conv'' data in Figure 3A is specifically from GF mice conventionalized on P21. This error in the text has also been corrected online.Overall, these changes have no bearing on the experimental results or conclusions presented in the manuscript. We apologize for any inconvenience that these errors have caused.

Amyloids are a class of protein with unique self-aggregation properties, and their aberrant accumulation can lead to cellular dysfunctions associated with neurodegenerative diseases. While genetic and environmental factors can influence amyloid formation, molecular triggers and/or facilitators are not well defined. Growing evidence suggests that non-identical amyloid proteins may accelerate reciprocal amyloid aggregation in a prion-like fashion. While humans encode ~30 amyloidogenic proteins, the gut microbiome also produces functional amyloids. For example, curli are cell surface amyloid proteins abundantly expressed by certain gut bacteria. In mice overexpressing the human amyloid α-synuclein (αSyn), we reveal that colonization with curli-producing Escherichia coli promotes αSyn pathology in the gut and the brain. Curli expression is required for E. coli to exacerbate αSyn-induced behavioral deficits, including intestinal and motor impairments. Purified curli subunits accelerate αSyn aggregation in biochemical assays, while oral treatment of mice with a gut-restricted amyloid inhibitor prevents curli-mediated acceleration of pathology and behavioral abnormalities. We propose that exposure to microbial amyloids in the gastrointestinal tract can accelerate αSyn aggregation and disease in the gut and the brain.

Background. Recommendations for promoting mental health during the COVID-19 pandemic include maintaining social contact, through virtual rather than physical contact, moderating substance/alcohol use, and limiting news and media exposure. We seek to understand if these pandemic-related behaviors impact subsequent mental health. Methods. Daily on-line survey data were collected on adults during May/June 2020. Measures were of daily physical and virtual (on-line) contact with others; substance and media use; and indices of psychological striving, struggling and COVID-related worry. Using random-intercept cross-lagged panel analysis, dynamic within-person cross-lagged effects were separated from more static individual differences. Results. 1148 participants completed daily surveys (657 [57.2%] females, 484 [42.1%] males; mean age 40.6 [SD 12.4] years). Daily increases in news consumed increased COVID-related worrying the next day (cross-lagged estimate=0.034 [95% CI 0.018 to 0.049], FDR adjusted p=0.00005) and vice versa (0.03 [0.012 to 0.048], FDR-adjusted p=0.0017). Increased media consumption also exacerbated subsequent psychological struggling (0.064 [0.03 to 0.098], FDRadjusted p=0.0005). There were no significant cross-lagged effects of daily changes in social distancing or virtual contact on later mental health.Conclusions. We delineate a cycle wherein daily increase in media consumption results in a subsequent increase in COVID-related worries, which in turn increases daily media consumption. Moreover, the adverse impact of news extended to broader measures of