Dual-trap Raman tweezers for probing dynamics and heterogeneity of interacting microbial cells

We report on development of dual-trap Raman tweezers for monitoring cellular dynamics and heterogeneity of interacting living cells suspended in a liquid medium. Dual-beam optical tweezers were combined with Raman spectroscopy, which allows capturing two cells that are in direct contact or closely separated by a few micrometers and simultaneously acquiring their Raman spectra with an imaging CCD spectrograph. As a demonstration, we recorded time-lapse Raman spectra of budding yeast cells held in dual traps for over 40 min to monitor the dynamic growth in a nutrient medium. We also monitored two germinating Bacillus spores after the initiation with L-alanine and observed their heterogeneity in the release of CaDPA under identical microenvironment.