Providencia stuartii (commonly P. stuartii), is a Gram negative bacterium that is commonly found in soil, water, and sewage. P. stuartii is the most common of the 5 species found in the genus Providencia, with Providencia rettgeri, Providencia alcalifaciens, Providencia rustigianii, P heimbachae. Providencia stuartii can be incubated at 37°C in nutrient agar or nutrient broth. P. stuartii is the genomic source for the restriction endonuclease, PstI.