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SIGNS OF BACTERIA

If you suspect that a spot or lesion has been caused by a bacterial infection, and you have access to a microscope, then you can confirm your suspicion by looking for BACTERIAL STREAMING. Cut the lesion from the leaf and place it on a microscope slide in a drop of water. Slice through the lesion with a razor blade. If bacteria are present they will "stream" out from the cut edges of the lesion. In this photo, the grainy material in the upper half the photo is a mass of bacterial cells that have streamed from a lesion (the dark mass at the bottom of the slide). Often large numbers of streaming cells will be particularly visible where veins have been cut. While this technique will not identify exactly which bacterium is involved in the disease, it can provide a useful clue that the disease is bacterial in nature.