Science Buddies: "Ask an Expert"

Ok, my project is due Feb.20, but I think my experiment will take a while to be observed. Its: Who has more bacteria in their mouth:Humans or Canines?


So, First I poured Agar into a new marked petri dish. Then I swabed a humans mouth and lightly rubbed it over the marked spot in the petri dish. Then I covered the dish wih a lid. I then sat it in a room temp. room for the bacteria to grow. Is this correct??? PLEASE RESPOND ASAP

Hi,

If you incubate your plates at room temperature, you will select for the bacteria that can grow at ambient temperature. Since dogs and humans have a higher body temperature, the bacteria you would expect to isolate would probably have an optimum temperature of about 37 degrees Centigrade. So it would be better to incubate at a higher temperature. However, if this is not possible, you still have a controlled experiment if both sets of plates are grown at the same temperature. With bacteria isolated from a natural setting, you will grow a different population ambient, 37 degrees, under anaerobic condition, and with different growth media, etc.

I hope this helps.

Donna Hardy

Remember to turn your plate upside down when you incubate it. Otherwise, condensation me form on the lid, dribble down onto your cultures, and make a mess.

I suggest you also seal the sides of your plates with tape or saran wrap. You could potentially isolate some dangerous bacteria--things that aren't a problem when you have a few of them, but could make someone sick when you have lots of them in a bacteria colony.

Hi!
I definitely agree, you must be very careful when working with bacterial colonies, especially when they are grown in such concentration. Remember to have supervision and to adhere to any safety and laboratory rules set forth by your teacher or the science fair. In addition, room temperature would be the optimal temperature because this would most accurately simulate the environment of a human or a canine. Best of luck!