Motile and Chemotactic Minicells and Minicell-Driven Biohybrids Engineered for Active Cargo Delivery

Bacterial minicells
are submicrometer-sized spherical compartments
produced by bacteria as a result of aberrant cell division. Minicells
have a similar cellular composition to the parental bacteria but lack
chromosomal DNA and are thus unable to proliferate. Due to that, minicells
have attracted attention as potential means of effector delivery in
bioengineering and biomedical applications. However, until now, the
efficiency of delivery by minicells has been limited by passive collisions
with their targets. To develop minicell-based active delivery, here
we engineer Escherichia coli strains
generating motile minicells with enhanced swimming properties by introducing
genetic modifications specifically targeting flagella number, length,
and rotation speed. The engineered minicells preserve motility over
an extended period of time and, in contrast to parental E. coli cells, increase their swimming speed for
the intermediate viscosity of the medium. Despite their small size,
minicells show an efficient chemotactic response and utilize the same
chemotactic strategy as parental E. coli cells. Moreover, we develop a procedure for conjugating minicells
with cargo particles and demonstrate that such minicell-driven biohybrid
swimmers are chemotactic and thus capable of actively accumulating
at the source of an attractant. These engineered chemotactic minicells
and minicell-based biohybrids can serve as cargo delivery platforms
with active targeting, thus overcoming the challenges posed by nontargeted
therapies.