Type III secretion system (T3SS) effector proteins are primarily recognized for binding host proteins to subvert host immune response during infection. Besides their known host target proteins, several T3SS effectors also interact with endogenous bacterial proteins. Here we demonstrate that theSalmonellaT3SS effector glycosyltransferase SseK1 glycosylates the bacterial two-component response regulator OmpR on two arginine residues, R15 and R122. Arg-glycosylation of OmpR results in reduced expression ofompF, a major outer membrane porin gene. Glycosylated OmpR has reduced affinity to theompFpromoter region, as compared to the unglycosylated form of OmpR. Additionally, theSalmonella ΔsseK1mutant strain had higher bile salt resistance and increased capacity to form biofilms, as compared to WTSalmonella, thus linking OmpR glycosylation to several important aspects of bacterial physiology.