Arginine impacts aggregation, biofilm formation, and antibiotic susceptibility in .

is a commensal bacterium in the gastrointestinal tract (GIT) of humans and other organisms. also causes infections in root canals, wounds, the urinary tract, and on heart valves. metabolizes arginine through the arginine deiminase (ADI) pathway, which converts arginine to ornithine and releases ATP, ammonia, and CO. arginine metabolism also affects virulence of other pathogens during co-culture. may encounter elevated levels of arginine in the GIT or the oral cavity, where arginine is used as a dental therapeutic. Little is known about how responds to growth in arginine in the absence of other bacteria. To address this, we used RNAseq and additional assays to measure growth, gene expression, and biofilm formation in OG1RF grown in arginine. We demonstrate that arginine decreases biofilm production and causes widespread differential expression of genes related to metabolism, quorum sensing, and polysaccharide synthesis. Growth in arginine also increases aggregation of and promotes decreased susceptibility to the antibiotics ampicillin and ceftriaxone. This work provides a platform for understanding of how the presence of arginine in biological niches affects physiology and virulence of surrounding microbes.