Abstract

In bulk studies of microalgae, we are forced to assume that all cells exhibit identical properties to a measurable average value. This is very unlikely to be a realistic assumption – all biological processes should have a degree of stochasticity, even when cells are genetically identical. Individual cell studies allow us to evaluate the extent of this stochasticity. C. reinhardtii cells accumulate TAGs (triacylglycerides) as discreet lipid bodies when placed under nitrogen stress. This has been well characterised in bulk – it is an important process to understand, since TAGs are a feedstock for biodiesel production. I have analysed this lipid accumulation process using three different single-cell screening techniques – confocal microscopy, flow cytometry and microdroplet screening. All techniques reveal that there is considerable variation in the amount of storage lipid per cell. The reliability and efficiency of these three single-cell screening methods have been compared. Microdroplet technology can also be used as a cell sorting platform – droplets containing cells with desirable fluorescence properties can be identified and sorted into a separate collection channel for further analysis. So far, the microdroplet sorting platform has been used to sort fluorescent droplets, and to select cell-containing droplets from empty one based on chlorophyll fluorescence. The sorting platform is currently being optimised to identify and sort high lipid producing cells for further analysis.