Characterization of the rgg499 locus in Lactobacillus acidophilus

Bacterial communities present in diverse environmental conditions can respond to signals or stresses using quorum sensing (QS). QS involves production of a signal that can be recognized via cell surface or internal receptors. We are focused on a small family of transcriptional regulators called Rgg and their cognate small hydrophobic peptides (SHP), specifically, three predicted QS systems present in the human commensal Lactobacillus acidophilus. Rgg QS systems have been described in other Gram-positive organisms and they can promote responses such as biofilm formation and toxin production. We aim to characterize the Rgg499 predicted QS system. Our preliminary work suggests rgg499 is in a six-gene operon with another regulator (496) and a potential peptide (495). This predicted operon is located next to a carbohydrate utilization locus. We hypothesize that Rgg499 may have effects on this operon given that sugars have acted as signals for other Rgg QS systems. We are currently testing the effects of various carbohydrates and small molecules on L. acidophilus and changes in rgg transcriptional expression using luciferase reporters in a heterologous host