Science Buddies: "Ask an Expert"

Is it possible to identify specific types of bacteria in water under a microscope? If not, is there another way I could?

Hi,

With a high powered microscope, you can stain bacteria and classify them as Gram-positive or Gram-negative and you can identify their size and shape, but you can’t identify the specific bacterium in the sample. There are selective growth media to help identify certain types of bacteria, like coliforms, but most of the time identification requires conducting a number of tests, including staining, fermentation of sugars, and utilization of specific nutrients. What were you thinking about doing or what question are you trying to answer? What types of water samples do you want to test? Do you have access to a laboratory?

Donna Hardy

Hi Pmkpac,

Yes, you can. Like Donnahardy said, you can stain for gram-positive or gram-negative bacteria. Besides that, you can also look at differet types of cell surface markers on bacteria by staining them (using immunohistochemistry) to determine what is expressed on the cell surface. You can also extract their RNA or DNA and classfiy them by that.

Hope that helps!

-Sam