A CONVENIENT METHOD TO MAINTAIN UNICELLULAR GREEN-ALGAE FOR LONG TIMES AS STANDING LIQUID CULTURES

A simple procedure is described to maintain unicellular green algae as slow growing standing liquid cultures for relatively long times. With this method the cultures of Chlorella pyrenoidosa, Chlorella vulgaris , Selenastrum capricornutum, Scenedesmus subspicatus, which are genera lly used for ecotoxicity testing were maintained viable and stable for more than 12 months in dim light at relatively low temperatures witho ut shaking. During storage no regular subculturing or transfer to fres h medium was required. For storage of liquid cultures wide mouth Erlen meyer flasks or tissue culture flasks (with membranes for contaminatio n free aeration) were used. To increase cell survival and stability va rious adsorption materials or stabilizers such as activated charcoal a nd trehalose were added to cell suspensions. For recultivation small a mounts of inoculum were transferred to fresh medium and regrowth of ce lls required no prolonged incubation. The method is useful for routine work as it provides a continuous source of ready inoculum for ecotoxi city testing and other purposes. The cultures can be maintained for lo ng times in a simple way at low cost requiring no specialized equipmen t.