Suppose you had a bacterial sample of an unknown species. you perform a gram stain and observe purple rods. what can you conclude about the bacteria?

The answer is gram-positive

Gram staining could be used to know whether the microorganism is having a thick peptidoglycan layer or not. A thick layer of peptidoglycan will retain the crystal violet stain, make the microorganism become purple when observed using microscope. If the peptidoglycan is too thin, the color will fade and the bacteria will retain pink color from safranin.