Stickiness to Glass: Circadian Changes in the Cell Surface of Chlamydomonas reinhardi

Abstract

Conditions were found in which Chlamydomonas reinhardi exhibits a circadian alteration of its cell surface, measured as ability to stick to glass. Under these same conditions the cells also show circadian rhythms of cell division and release of daughter cells. The three rhythmic phenomena were shown to have typical properties of rhythms controlled by the biological clock. The rhythm of stickiness was used to demonstrate that in a mixed culture containing two cell populations with natural periods differing by 2 to 3 hours, the cells did not mutally entrain each other and that this rhythm could be successfully applied in an enrichment procedure for mutants of the biological clock. Stickiness was shown to be independent of growth and motility of the cells and unaffected by red or far red illimination. Minimally sticking cells did not affect the sticking of maximally sticking cells in a mixed culture; nor was there a progressive increase in stickiness shown at the minimum from one cycle to the next in a pure culture. These results indicate that sticking probably is not mediated by long lived adhesive material or enzymes excreted into the medium. Several tests of the sensitivity of stickiness to replacement of the growth medium by distilled water or water containing various compounds suggest that ions might play an important role in the sticking reaction.