An extremely simple and effective colony PCR procedure is established for both gram-negative and gram-positive bacteria, yeasts, and microalgae. Among the four lysis buffers examined, Y-PER is observed to be more effective than Tris/EDTA, 0.2 % SDS, and 10 mM EDTA in the extraction of PCR-quality genomic DNA from those microorganisms. Vortexing or pipetting agitation of the cells in Y-PER for 5-10 s was sufficient to release genomic DNA for all the test bacteria and yeasts, and most microalgae. Additional incubation at 98 A degrees C for 5 min for further cell disruption was essential only for Chlorella vulgaris due to its notoriously rigid cell wall.