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Bacillus Subtilis Colony Characteristics

Bacteria live in groups called colonies that when cultured can form patches visible to the naked eye. Bacteria colonies are created from one organism and are thus genetically identical. The many bacteria in a colony act together, making the colony like a single organism. Bacillus subtilis is a bacteria used to study the colony characteristics of bacteria. It grows quickly on agar in most any condition, and colonies have distinct characteristics.

  1. What Is It?

    • Bacillus subtilis is one of many bacteria found naturally inside the human body. It is also common on vegetables and other plants and in the soil. The bacteria are only harmful when the colonies grow too large and begin infecting the body. Each Bacillus subtilis is rod-shaped, with a flagellum, or hairlike tail, that propels it.

    Colony Traits

    • All characteristics of Bacilus subtilis can be observed while the bacteria grow on an agar surface. A colony of Bacillus subtilis is traditionally circular, with ragged edges, colored cream or white. The bacteria spread out from the center, keeping the ragged circular shape of the colony. You can see the individual organisms moving together under a microscope. The individual bacteria travel in bands, moving the colony together. Bacilus subtilis can only move in one direction -- forward.

    Agar-Related Variations

    • Bacillus subtilis colonies are affected by the quality of the agar on which they are grown. A colony doesn't die if the agar isn't ideal -- the bacteria are resilient, able to live in both dry and very moist conditions. On dry agar, the colony takes a circular shape but forms branches that radiate from the center. The bacteria move in a line, lubricating the agar for those behind it. In addition, Bacillus subtilis produces spores on dry agar.

      If more moisture is added to dry agar, a bulls-eye formation and more ragged circular shape will result. When agar is very moist, the colony actually grows into it, burrowing down and then forward and forming layers

    Colonial Effects on Humans

    • When Bacillus subtilis colonies grow to more than the body can handle, they can cause an infection also known as food poisoning. An infection is possible after a person ingests foods containing the bacteria. Symptoms include diarrhea, nausea and vomiting. According to a Huntingdonshire, Great Britain District Council announcement on Bacillus subtilis poisoning, the affected person can begin to feel symptoms in as little as 10 minutes after ingesting the contaminated foods. The symptoms can last for two days.

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