Unravelling the photoreceptor underlying light-switchable adhesion of <i>Chlamydomonas</i> by micropipette force measurements

Bioadhesion is a ubiquitous phenomenon for many living systems such as mussels, bacteria or microalgae. In this presentation, we focus on the adhesion of the biflagellated unicellular model organism Chlamydomonas reinhardtii. We discovered that Chlamydomonas exhibits light-switchable adhesion [Kreis et al., Nature Physics, 2018], in which its flagella adhere to any type of surface [Kreis et al., Soft Matter, 2019] under blue but not under red light. Our goal is to unravel the blue-light sensitive photoreceptor that triggers this highly specific light-regulated behaviour. We employ in vivo micropipette force measurements [Backholm & Bäumchen, Nature Protocols, 2019] on single wild-type cells to precisely identify the full spectral response of flagellar adhesion using narrow bandpass filters and thereby detect the characteristic action spectrum of the photoreceptor associated to cell adhesion. We also present adhesion force measurements of single mutant cells, for which a specific photoreceptor was deleted by means of modern gene editing tools.