New method for discovery of starch phenotypes in growing microalgal colonies

To identify algal strains with altered starch metabolism from a large pool of candidates of growing algal colonies, we have developed a novel, high-throughput screening tool by combining gaseous bleaching of replica transferred colonies and subsequent iodine staining to visualize starch. Screening of healthy growing colonies of microalgae has not been possible previously because high levels of chlorophyll make the detection of starch with an iodine stain impossible. We demonstrated that chlorine dioxide (ClO(2)) removes essentially all chlorophyll from the colonies and enables high-throughput screening of, for example, a population of mutagenized cells or a culture collection isolated in a bioprospecting project.