Klebsiella pneumoniae is as an industrial important host for the production of compounds such as 1,3-propanediol,2,3-butanediol and 3-hydroxypropionic acid.Quorum sensing(QS)is a cell density dependent signaling mechanism and bacteria judge their overall density to regulate diverse activities through QS system.K.pneumoniae has been characterized to harbor type II QS system.In this work,ygaG gene required for QS autoindecer synthesis in K.pneumoniae was cloned and ligated into the expression vector pET-28a.The resulted plasmid was then transformed into the host K.pneumoniae and the recombinant strain K.pneumoniae(pET-28a-ygaG)was obtained.The growth rate,glycerol consumption and metabolites production of the K.pneumoniae(pET-28a-ygaG)were analyzed in shake flask culture with initial glycerol concentration of 40 g/L.The cell growth was suppressed by the over-expression of ygaG,and the yield of 3-hydroxypropionic acid decreased from 0.3 g/L to 0.15 g/L in ygaG over-expression strain compared to the control.However,the yield of lactic acid of the recombinant strain reached to 0.9 g/L,whereas the control strain only yielded 0.5 g/L.This is the first study on the relationship between QS system and metabolites production in K.pneumoniae.