Roles of the Crp/Fnr Family Regulator ArcR in the Hemolysis and Biofilm of .

is an opportunistic human pathogen that is often involved in severe infections such as pneumonia and sepsis in which bacterial virulence factors play a key role. Infections caused by are often difficult to eradicate, particularly when they are associated with biofilm. The physiological roles of the Crp/Fnr family regulator ArcR are elusive in . In this study, it was found that the deletion of increased the hemolytic ability and biofilm formation in . Differential gene expression analysis by RNA-seq and real-time quantitative reverse transcription PCR showed that genes associated with hemolytic ability ( and ) and biofilm formation ( and ) were significantly upregulated compared with those in the wild-type strain. The results revealed that ArcR regulated the expression of the and operon by binding to their promoter regions, respectively. This study provided new insights into the functional importance of ArcR in regulating the virulence and biofilm of