You must design a valid experiment to show that there are microorganisms in the air. what would be your dependent variable?
sterilized broth
growth of organisms in the broth
exposure to microorganisms in the air

bacteria could be both, harmful and to us. harmful bacteria could make us sick and probably even by getting the chances of getting a disease, but good bacteria fight it off with your immune system. there is always bacteria everywhere we go. we need to make sure to wash our hands after using the restroom, before eating, after eating, after petting an animal too. so you see, bacteria is everywhere and is harmful or . i hope this . : ) : ) : )