SiCTeC: An inexpensive, easily assembled peltier device for rapid temperature shifting during single-cell imaging

Abstract

Single-cell imaging, combined with recent advances in image analysis and microfluidic technologies, have enabled fundamental discoveries of cellular responses to chemical perturbations that are often obscured by traditional liquid-culture experiments. Temperature is an environmental variable well known to impact growth and to elicit specific stress responses at extreme values; it is often used as a genetic tool to interrogate essential genes. However, the dynamic effects of temperature shifts have remained mostly unstudied at the single-cell level, due largely to engineering challenges related to sample stability, heatsink considerations, and temperature measurement and feedback. Additionally, the few commercially available temperature-control platforms are costly. Here, we report an inexpensive (110) and modular Single-Cell Temperature Controller (SiCTeC) device for microbial imaging based on straightforward modifications of the typical slide-sample-coverslip approach to microbial imagingthat controls temperature using a ring-shaped Peltier module and microcontroller feedback. Through stable and precise (0.15C) temperature control, SiCTeC achieves reproducible and fast (12 min) temperature transitions with programmable waveforms between room temperature and 45C with an air objective. At the devices maximum temperature of 89C, SiCTeC revealed that Escherichia coli cells progressively shrink and lose cellular contents. During oscillations between 30C and 37C, cells rapidly adapted their response to temperature upshifts. Furthermore, SiCTeC enabled the discovery of rapid morphological changes and enhanced sensitivity to substrate stiffness during upshifts to nonpermissive temperatures in temperature-sensitive mutants of cell-wall synthesis enzymes. Overall, the simplicity and affordability of SiCTeC empowers future studies of the temperature dependence of single-cell physiology. Copyright: