3-9 The Endospore Stain
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Cells of Bacillus, Desulfotomaculum and Clostridium (and several other, lesser-known genera--see Bergey's Manual) may, as a response to nutrient limitations, develop endospores that possess remarkable resistance to heat, dryness, irradiation and many chemical agents. Each cell can produce only one endospore. It is therefore not a reproductive spore as seen for some organisms such as Streptomyces and most molds. The endospore is essentially a specialized cell, containing a full complement of DNA and many proteins, but little water. This dehydration contributes to the spores resistance and makes it metabolically inert. The endospore develops in a characteristic position (for its species) in the vegetative cell. Eventually the cell lyses, releasing a free endospore. For more information on endospores, read the Figure 3-7.
Endospore Stain Procedure
Endospore stains require heat to drive the stain into the cells. For a endospore stain to be successful, the temperature of the stain must be near boiling and the stain cannot dry out. Most failed endospore stains occur because the stain was allowed to completely evaporate during the procedure.
Figure 3-12 shows a photomicrograph of an endospore stain.
Figure 3-12 The Endospore Stain
A photomicrograph of an enodspore stain. Spores present in the picture stain green, while the vegetative cells stain red. A) Staphylococcus epdiermidis which does not form endospores. B) The endospore-forming rod, Bacillus cereus.