Synchronous cultures of micro-organisms: large-scale preparation by continuous-flow size selection.

The separation of the smallest cells from an exponentially growing culture by passage through a continuous flow centrifuge rotor under controlled conditions of rotor speed and flow rate, provides a simple method for the rapid production of large-scale synchronous cultures. The effluent from the rotor, containing the smallest-sized class of organisms, still suspended in their growth medium and still growing undisturbed throughout this rapid procedure, provides a culture which goes on to exhibit synchronous cell division. Successfully applied to budding and fission yeasts and to amoeboid and ciliated protozoa, this procedure ti potentially applicable to any non-filamentous, non-aggregating, unicellular organism or to cells of higher plants or animals growing in liquid tissue-cultures.