Alcohol Use Disorder (AUD) is a devastating disease with negative health, social, and economic consequences. AUD susceptibility is regulated by both genetic and non-genetic factors. While advances in genetics and genomics have allowed us to gain insight into the role of host genes in AUD, environmental contributions to AUD such as the microbiome, have not been well defined. The gut microbiome represents a non-genetic contributor to many neuro-psychological conditions. Although several studies have established that acute and chronic alcohol use is associated with dysbiosis of the gut microbiome, no study has investigated whether the basal gut microbiome (before drinking) influences the risk of developing excessive drinking. Work by us and others showed that genetically identical C57BL/6J (B6J) mice varied widely in alcohol intake and blood ethanol concentration (BEC). Our microbiome and metabolite analysis showed mice with lower levels of butyrate in stool, prior to alcohol intake, had higher levels of alcohol intake and BEC, and harbored a lower level of Clostridia bacteria, compared to low-drinking mice. Butyrate is a group of short-chain fatty acids (SCFAs) produced by gut microbes through fermentation. Clostridia possess strong immune-modulatory properties and are a major producer of butyrate. Butyrate can function as histone deacetylase inhibitors (HDACi), which affect gene expression by histone modification. Epigenetic regulation of gene expression has emerged as a potentially important mechanism in the regulation of alcohol intake. We hypothesize that the gut microbiome /microbial metabolites can regulate chromatin plasticity in brain, and subsequently altering neuronal transcription and eventually affecting behavior. In Aim 1, we will establish correlations between the gut microbiome/metabolites, alcohol drinking, and epigenetic alterations of B6J mice. This aim will confirm our preliminary findings with a large sample size and extend to epigenetic characterization of mice with differential drinking. In Aim 2, we will test whether high- and low- drinking phenotypes are transmissible using fecal transplantation, and further test whether specific microbes and/or metabolites are responsible for differential drinking behavior. Epigenetic characterization including histone modification and global gene expression will be performed to gain mechanistic insight into the influence of the microbiome on alcohol preference. Our proposed work will test the role of the gut microbiome in alcohol preference, improve our understanding of the etiology of AUD, and lay the groundwork to develop novel therapeutic strategies for AUD, including pro- and/or prebiotic manipulation of the gut microbiome.