When living with a partner, you might be sharing more than just the same home, lifestyle, and interests. You might also share various microscopic organisms residing on and in you.

Gram staining is one way scientists can identify bacteria. Gram-positive bacteria, such as Staphylococcus, appear blue or purple under a microscope when scientists apply a stain. Conversely, ...

Gram-positive bacteria have thick cell walls. A Gram stain test, which involves a chemical dye, stains the bacterium’s cell wall purple. On the other hand, gram-negative bacteria stain pink instead.