Q:

Why are agar plates turned upside down when incubated?

A:

Quick Answer

Before they are inoculated and incubated, agar plates are turned upside down so that any condensation that might be present on the lid does not drip down into the culture medium. The agar plate lid is not placed on a counter top or elsewhere, and its interior not touched, so that no airborne contaminants can affect the culture. When placed into the incubator, the agar plate remains upside down so that the culture continues to be protected from possible contamination.

Know More

Full Answer

Agar plates are Petri dishes that contain a medium suitable for culturing microorganisms. They may also be called blood agar plates when they contain red blood cells, often from a horse or sheep, which are often used as a nutrient. Because some bacteria can only digest red blood cells that have already been broken down, some agar plates contain a preheated medium, which breaks down the blood cells and gives them a brownish color. This is often referred to as "chocolate agar" because of its color, and it does not reflect the presence of chocolate as a growth medium.

Agar plates may also contain antibiotics that will prohibit the growth of certain strains of bacteria. This serves to make the plate selective for identifying specific kinds of bacteria by eliminating the possibility of growth by other strains. These are called "restrictive" or "selective" plates. Those agar plates that will allow the growth of whatever organisms they are inoculated with are referred to as "permissive" plates.

Learn more about Biology

Related Questions

  • Q:

    What are condensation nuclei?

    A:

    Condensation nuclei are tiny particles of solid or liquid in the atmosphere that trigger water vapor to begin condensing into water droplets and forming clouds. Any particles that are attractive to water molecules, namely charged or polar particles, are suitable nuclei, but under normal conditions they must be large enough to likely encounter a water molecule. Once this occurs, each additional molecule helps the nuclei attract more molecules.

    Full Answer >
    Filed Under:
  • Q:

    What causes condensation?

    A:

    Condensation occurs when a vapor gas cools beyond its saturation limit and liquid begins to form. Because the water vapor releases its heat during this process, condensation is a warming process.

    Full Answer >
    Filed Under:
  • Q:

    What is the difference between condensation and evaporation?

    A:

    Evaporation happens when liquid turns into gas whereas condensation occurs when gas changes to liquid. The higher the temperature of the liquid, the higher the rate of evaporation becomes. In contrast, the condensation rate rises when the temperature of gas lowers.

    Full Answer >
    Filed Under:
  • Q:

    How do you fix your Internet connection?

    A:

    Fix an Internet connection by checking for obvious reasons for the problem, such as an unplugged cable or the Wi-Fi on your computer being turned off. Check to make sure the problem isn't a broken website link, a block from a firewall or incorrect configuration of your network. Cycle your system, and call your Internet provider if nothing else works.

    Full Answer >
    Filed Under:

Explore