Quorum signaling via Al-2 communicates the "metabolic burden" associated with heterologous protein production in Escherichia coli

Recent reports have shown that bacterial cell-cell communication or quorum sensing is quite prevalent in pathogenic Escherichia coli, especially at hi gh cell density; however, the role of quorum sensing in nonpathogenic E. co li is less clear and, in particular, there is no information regarding the role of quorum sensing in overexpression of plasmid-encoded genes. In this work, it was found that the activity of a quorum signaling molecule, autoin ducer-2 (Al-2), decreased significantly following induction of several plas mid-encoded genes in both low and high-cell-density cultures of E. coli. Fu rthermore, we show that Al-2 signaling level was linearly related to the ac cumulation level of each protein product and that, in general, the highest rates of recombinant protein accumulation resulted in the greatest attenuat ion of Al-2 signaling. Importantly, our findings demonstrate for the first time that recombinant E. coli communicate the stress or burden of overexpre ssing heterologous genes through the quorum-based Al-2 signaling pathway. ( C) 2001 John Wiley & Sons, Inc.