text: i want to know kinds of helpful and harmful bacteria?   when viewed under a high-powered microscope, good bacteria and bad bacteria have distinctly visible markers.  good bacteria are characterized by a little happy smiley-face, located on the front or even the top of each such organism.  on the other hand, bad bacteria have a tiny, mean frowny-face.  don't be confused by the use of these highly technical terms; that's just how it is done by bacteria professionals.    now you know.