Growing Bacteria

The coronavirus behind the pandemic can linger on any surfaces anywhere even inside our house, therefore we decided to do an experiment to see if our house was germ-free. First, we chose the places where we wanted to do the test (bathroom, kitchen, storage room, shoes cabinet and garage door). Then prepared 10 petri dishes filled with a solution made of beef bouillon powder, agar powder, sugar and water. 2 petri dishes (1 opened lid and 1 closed lid) were put in each place for a few hours. After that we put all the petri dishes into a box and let them incubate. By the size of our petri dish, we computed the constant divisor to get the colony-forming unit (CFU) of each dish for the first 3 days of observation. Starting day 4, the colony or bacteria growth started to merge so it was not possible for us to count each growth. As predicted, open lid dishes had more bacteria growth than closed one because they were exposed to the open air. Even though the close lid ones did not get any exposure to the open air, they still got bacteria growth inside the dish. This proved to us that bacteria were indeed everywhere whether you could see it or not. This experiment indeed taught us the importance of cleanliness and proper hygiene.