Biological Clocks

Diatoms are an essential part of phytoplankton. The unicellular eukaryote has a cell wall made of silicate, the so-called frustule. Frustules are of physico-chemical and biological interest regarding their origin as well as technically because of their photonic properties. The frustules are divided into two thecae. During cytokinesis, a new, smaller theca is formed from each of the two thecae. As a result, the average size of the diatoms in the population decreases. After reaching a critical size, the diatoms either begin to reproduce sexually or die in subsequent generations.

This poses the questions of which mechanisms influence cytokinesis and when exactly does cell death occur? To answer these questions, the influence of environmental conditions is explored using synchronized cultures. In particular, light as a timer in the day-night cycle and the influence of the wavelength are examined. Furthermore, new techniques are developed which enable observation of individual cells and analysis of cytokinetic mechanisms.