Pseudomonas aeruginosa is a Gram negative bacterium. Separating the cell envelope compartments enables proteins to be localized to confirm where in the cell they function. Cell fractionation can also provide a first step in a protein purification strategy (Williams et al. https://www.markbroyard.com/hot-save-turbo-air-m3f24-1-n-29-wide-m3-series-reach-in-freezer-featuring-one-solid-door-energy-star-on-sale-top-super/