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

• Published in: Light, science & applications science & applications, 2016-10, Vol.5 (10), p.e16158-e16158
• Main Authors: S Bezryadina, Anna, C Preece, Daryl, Chen, Joseph C, Chen, Zhigang
• Format: Article
• Language: English
• Subjects: 639/624/1107/1110; 639/624/1111/55; Applied and Technical Physics; Atomic; Bacteria; Biofilms; Cell adhesion & migration; Classical and Continuum Physics; Infections; Lasers; Molecular; Optical and Plasma Physics; Optical Devices; Optics; Original; original-article; Photonics; Physics; Physics and Astronomy
• ISSN: 2047-7538; 2095-5545; 2047-7538
• DOI: 10.1038/lsa.2016.158

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 the 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. Optical tweezers: bacterial binding ‘Tug-of-war’ optical tweezers that can trap, stretch and pull apart a cluster of bacteria cells could aid studies of biofilms. Anna Bezryadina and co-workers in the USA and Australia used their tweezers to investigate the strength of intercellular adhesion for clusters of rod-shaped Sinorhizobium meliloti cells, a common strain of plant symbiont. They estimate that a pulling force of at least 5 piconewtons is needed to break up a cluster of S. meliloti cells, although they consider that the precise adhesion strength depends on the growth medium. The team's ‘tug-of-war’ tweezer design splits a single light beam into a diverging pair of elongated trapping beams, which hold each end of a rod-shaped bacterium or a cluster. The researchers suggest that the tweezers may also be useful for stretching DNA molecules.