In formal descriptions of the germ-fighting powers of antibacterial and biocidal products, the terms "Gram positive" and "Gram negative" are used as a way to categorize bacteria. While there are estimated to be over 10,000 species of bacteria, they can be categorized into a few helpful categories.
One of those categories has to do with the structure of the cell membrane. All the known bacteria fit into one of two categories of cell membrane structure: Gram-positive or Gram-negative. But what does that mean?