Optical disassembly of cellular clusters by tunable tug-of-war tweezers

TL;DR

This paper introduces tunable tug-of-war optical tweezers capable of measuring and manipulating bacterial cell-cell adhesion within biofilms, providing a new tool for studying biofilm formation and disassembly.

Contribution

The study presents a novel optical tweezer technique that can apply lateral forces to bacterial clusters without tethering, enabling direct assessment of intercellular adhesion in biofilms.

Findings

Tug-of-war tweezers can trap and stretch rod-shaped bacteria.

Intercellular adhesion strength varies with growth medium.

Technique offers a new method for biofilm analysis.

Abstract

Bacterial biofilms underlie many persistent infections, posing major hurdles in antibiotic treatment. Here, we design and demonstrate tug-of-war optical tweezers that can facilitate assessment of cell-cell adhesion - a key contributing factor to biofilm development, thanks to the combined actions of optical scattering and gradient forces. With a customized optical landscape distinct from that of conventional tweezers, not only can such tug-of-war tweezers stably trap and stretch a rod-shaped bacterium in the observing plane, but, more importantly, they can also impose a tunable lateral force that pulls apart cellular clusters without any tethering or mechanical movement. As a proof of principle, we examined a Sinorhizobium meliloti strain that forms robust biofilms and found that the strength of intercellular adhesion depends on the growth medium. This technique may herald new photonic tools for optical manipulation and biofilm study, as well as other biological applications.