Screening algal mutant colonies with altered thylakoid electrochemical gradient through fluorescence and delayed luminescence digital imaging

A digital imaging instrument intended to monitor fluorescence and delayed luminescence of algal colonies grown on Petri plates is described. The system includes light-emitting diodes, a cooled line transfer charge-coupled device (CCD) camera, and a personal computer. Software developments were made to capture pictures and kinetics in real time during illuminations. This instrument makes the fluorescence induction kinetics of individual colonies readily accessible with a good time resolution. It offers a great refinement for screening colonies deficient in photosynthetic electron transfer thanks to appropriate computed fluorescence images. The high sensitivity of the instrument allows it to capture fluorescence images under non-actinic illuminations, and for the first time, delayed luminescence images, opening thus the way to screening mutants that have altered thylakoid electrochemical gradients.