Plasmon-Enhanced Fluorescence from Single Proteins in Living Bacteria

The sensitivity and resolution of single-molecule fluorescence imaging in biology are mainly limited by two known weaknesses of fluorescent proteins: label brightness and photostability. In this work, we use patterned gold substrates to achieve plasmon-enhanced emission from intrinsically fluorescent proteins in living pathogenic bacteria cells. By coupling membrane-bound single fluorescent protein fusions to the virulence regulator TcpP in living <i>Vibrio cholerae</i> bacteria to extracellular gold nanotriangle arrays, we use plasmonics to improve our measurements of this important question in pathogenesis: how does <i>V. cholerae</i> produce its deadly toxin? Based on a simple experimental geometry, we observe a 1.3× enhancement in the rate of emission and a 1.4× enhancement in the number of photons detected prior to photobleaching. Furthermore, by enhancing both the rate of emission and the total number of photons detected from single-molecule fluorescent probes in live cells, we show that plasmon-enhanced fluorescence is a biocompatible, generalizable path to directly improve the resolution and trajectory lengths of single molecules in live cells