What are Endospores?

While bacteria are tiny, do not underestimate how tough they are! Bacteria from the genera Bacillus, Clostridium, and Sporosarcina have developed a clever strategy to preserve their DNA, or genetic material, when living in stressful, less-than-ideal environments. Examples of stressful conditions include if they don't get enough water and nutrition, if it is too hot, or if they are exposed to ultraviolet radiation. So what is this big idea? Endospores! These are cases of hardy keratin protein created within the cell, that protect the bacteria's DNA and save it for later. They are formed when the cell divides within itself- remember, bacteria reproduce by dividing and making more copies of themselves! Each bacterial cell forms one endospore. The spores are classified as terminal, subterminal, or central based on their location within the cell: terminal is at the end of the cell, subterminal is near the end, and central is in the center! When the cell degrades, the endospore will go out into the environment as a free spore. The spore can survive for a long time - up to hundreds of years- keeping the bacteria's genetic info intact. After the conditions become more favorable, the endospore will germinate, or produce a living/vegetative bacterial cell.

In the microbiology lab, if we want to find out if the bacteria can form endospores, we perform the endospore stain where we apply the stains malachite green and safranin to our bacteria. When we view the stained cells under the microscope, the cell will appear pink, and the endospores green.

Picture Source: austincc.edu