Ways & How

how to culture bacteria

how to culture bacteria

Bacteria are all around us, thriving in the environment, and getting on well on their own. Sometimes, we tend to forget that they’re there at all, and no matter how often we’re warned to wash our hands or to handle food properly by observing good sanitary practices, we tend to find this inconvenient and not bother to do so. Having overall good health can help make our immune systems strong enough to counter most attacks on our health so that we don’t feel its effect. That’s why we tend to take cleanliness and proper care for granted. Since bacteria can also not just be harmful but useful, many researchers use them in scientific experiments. But you don’t have to be a scientist to work with bacteria. But first, you would need to learn how to culture bacteria.

  1. Get materials. You’ll need Petri dishes, sterile swabs, packing tape, marker, and gloves. Petri dishes are round glass dishes with a top that allow you to grow your cultures without contamination from the environment. The kind you buy should contain agar medium and nutrients.

    to use, keep the Petri dishes stored upside down (with the cover on the bottom) in the refrigerator to keep condensation from dropping into the growing medium.

  2. An hour before you start working, remove the Petri dishes from the refrigerator and set them upside down in a safe place to allow them to get to room temperature. When the Petri dish is ready, you can collect samples. Using a sterile swab, collect samples from places you usually touch: a doorknob, stair railings, your phone, etc. You can even swipe it across your tongue, or your pet’s; use one swab per sample. Carefully streak the swab across your agar surface in an “S” pattern.

    Be careful not to tear the medium, and take care that nothing else touches the surface aside from the swab. If you want, you can gently press your bare fingers directly onto the agar surface to get a direct sample from your hand.

  3. Cover the Petri dish, tape it closed, and label each one carefully to identify the sample or source of the bacteria in it.

  4. Store the Petri dishes upside down in a safe, warm location—ideally a dark, warm cupboard—but not under direct sunlight or a heat source. Wait three to four days.

  5. Take out the Petri dishes and see how much bacteria has grown. You don’t have to open the cover. You could note the color, texture, shape, and other descriptions of the bacteria you observe, noting where you got the sample from.

  6. To clean the bacteria, put on gloves. Be careful in handling the Petri dish because it can make you sick. Do not open the dish near any food, drink, or food preparation area. Open the cover of the dish and pour in a tablespoon of bleach. Cover it back up and tilt the dish to spread the bleach inside so that the entire surface comes in contact with the bleach. Seal with tape, put in a trash bag, and dispose. Also dispose of the gloves, and wash your hands thoroughly.

Finding out how to culture bacteria is not as fascinating as actually growing them and observing the results. It can be a great experiment from which you can learn a lot. So get to growing.


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