The anticancer therapy
strategy mediated by tumor-targeting bacteria
needs better visualization tools for imaging and monitoring bacteria in vivo. The probiotic strain Escherichia
coli Nissle 1917 (EcN), one of the tumor-targeting
bacteria, leads to the potential application for cancer therapy. Here,
we report the development and application of a live, EcN-based imageable
vehicle for noninvasive in vivo bioluminescence imaging
in live mice. Firefly luciferase (Fluc) and luciferin-regenerating
enzyme (LRE), an enzyme that contributes to stable bioluminescence,
were functionally coexpressed in EcN. The recombinant EcN strain expressing
the genomically integrated Fluc-LRE cassette was demonstrated to be
a valuable tool for generating robust, continuous, and red-shifted
bioluminescence for bacterial tracking in vitro and in vivo, thus providing an optical tumor-targeting system
for the in vivo study of bacteria-assisted cancer
therapy. Additionally, in vivo imaging of the recombinant
EcN strain in the mouse intestinal tract indicated the potential of
this strain to be used as a tool in the study of gut.