Chlamydomonas is also amenable to transgenic approaches, , and the genome of this alga is now readily available and annotated. Chlamydomonas shows division by binary fission, where growth 2 n fold is followed by n divisions. Often reproducing asexually, under situations of synchrony (where division is separated from growth and restricted to the dark phase of a light:dark cycle ). Such approaches have the potential to radically change the resolution of our understanding of the cell cycle and the relationship to and modulation of cell size.Ĭhlamydomonas reinhardtii is a single celled algae and an established model in biofuel production (biohydrogen and triacylglycerol (TAG) accumulation), , evolution, and biochemistry. As a result, flow cytometric based methods for cell size selection would be compatible with a range of other methodologies. Chlamydomonas is both highly autofluorescent and amenable to transgenic approaches or the application of extrinsic fluorophores. Here we develop a method using flow cytometry in a model alga, which not only enables the separation of unstained cells based on cell size, but is capable of sorting individual cells into different media. All three of these approaches rest on the capacity to control for cell size in a high throughput and accurate way. Elucidating such processes further requires the ability to control a cell's environment, the use of transgenic approaches or chemical methods to control the cell cycle stage, in addition to species demonstrating short generation times and the ability to exert phenotypic selection. For example, the size that a cell grows to, as well as the dynamics of cell growth, exists as a response to intrinsic factors such as the molecular processes governing growth and division, as well as extrinsic factors mediated by the relationship between that cell and its environment that shape the evolution of cell growth. The extent and dynamics of cell growth and division represent a complex interplay of processes. Estimates demonstrate significant heritability of cell size in both gametes and vegetative cells, while a strong correlation between gametic and vegetative size suggests that selection on gamete size could be used to evolve vegetative size under experimental evolution. Furthermore, we demonstrate the use of autofluorescence properties of algae, and further support existing literature showing effective disruptive selection on size when incident light scatter and fluorescence parameters are combined as selection criteria. By selecting on size related characteristics in gametes, we are able to show the capacity for sensitive selection of small variations in cell size. Using three methods, we demonstrate the capacity to sort live cells without the need for extrinsic fluorophores. Here, we use cell sorting to demonstrate the utility of selecting on size in live gametes of the single celled algae Chlamydomonas reinhardtii an important model in cell cycle research, cell physiology and biofuel modelling. An emerging method for the measurement and collection of single cells based on cellular properties is flow fluorescence activated cell sorting (FACS). Existing approaches to measuring the size of single cells or, alternatively, disrupting the size distributions of populations, do not often allow the high throughput collection and separation of live cells post-measurement.