Pseudomonas stutzeri  Pseudomonas stutzeri is a Gram-negative soil bacterium that is motile, has a single polar flagellum, and is classified as bacillus, or rod-shaped. While this bacterium was first isolated from human spinal fluid, it has since been found in many different environments due to its various characteristics and metabolic capabilities. "P. stutzeri" is an opportunistic pathogen in clinical settings, although infections are rare. Based on 16S rRNA analysis, this bacterium has been placed in the "P. stutzeri" group, to which it lends its name. "P. stutzeri" is most easily differentiated from the other "Psuedomonas spp." in that it does not produce fluorescent pigments"." "P. mendocina, P. alcaligenes, P. pseudoalcaligenes", and "P. balearica" are classified within the same branch of pseudomonads as "P. stutzeri" based on 16S rRNA sequences and other phylogenetic markers. Of this group, "P. stutzeri" is most closely related to "P. balearica" and they can be differentiated not only by the 16S rRNA sequences, but also by the ability of "P. stutzeri" to grow above 42 °C. "P. stutzeri" has been isolated in many different locations, and since each strain is a little different based on where it was isolated, the "P. stutzeri" group contains many genomovars. This means that the many strains of "P. stutzeri" can be considered genospecies, which are organisms that can only be differentiated based on their nucleic acid composition. Burri and Stutzer first described "P. stutzeri" in 1895 and named the bacterium "Bacillus denitrificans II". Seven years later in 1902, Itersonion developed an enrichment culture for "P. stutzeri," which was later described by van Niel and Allen in 1952. The enrichment medium is a mineral medium with 2% nitrate and tartrate (or malate, succinate, malonate, citrate, ethanol, or acetate) grown under anaerobic conditions at 37 °C. The organism has been isolated from a wide variety of places such as human spinal fluid, straw, manure, soil, and canal water.