Fig. 4.

Selection of a hyperperforming Chlorella subpopulation based on division rate. (A) Single Chlorella were encapsulated into PicoShells and incubated under standard culturing conditions in a shaking flask to allow cells to produce greater numbers of cells . Colony-containing PicoShells from the top 15% of the Cy5 fluorescence distribution were selected by FACS and mechanically released from particles. Released cells were then recultured for further analysis. (B) From a particle population of 121,213 particles (3,839 containing colonies), 425 particles were selected. Selected particles were ruptured on top of a cell strainer, causing selected algae to be released into fresh culture media. This sample was regrown in an Erlenmeyer flask under standard culturing conditions for several days. (Scale bars: 100 µm.) (C) The selected population and an unselected population were seeded in separate flasks at the same concentration, and their cell concentrations were tracked for 4 d. The selected population had an 8% faster growth rate (10.2-h doubling times) than the unselected population (11.2-h doubling time) for the first 48 h after seeding before slowing down as the culture reached carrying capacity. Error bars represent the SD in the cell concentration at each time point between samples. (D) The largest difference in cell concentration was observed at 48 h after seeding (∼40% difference in cell concentration), a difference that can be visibly seen in the green color of the cultures. (E) The difference in growth was verified by measuring the chlorophyll density of each sample with a well-plate reader at 48 h after seeding. The selected population was measured to have a 27.6%-higher chlorophyll density (P < 0.05). Error bars represent the SD between the different wells used to measure the chlorophyll fluorescence at the 48-h time point. Ten wells were measured for each sample.