TAXONOMY: cellular organisms -> Bacteria -> Proteobacteria -> Gammaproteobacteria -> Enterobacteriales -> Enterobacteriaceae -> Proteus
Proteus is a genus of Gram-negative Proteobacteria. Proteus bacilli are widely distributed in nature as saprophytes, being found in decomposing animal matter, sewage, manure soil, and human and animal feces. They are opportunistic pathogens, commonly responsible for urinary and septic infections, often nosocomial. Three species—P. vulgaris, P. mirabilis, and P. penneri—are opportunistic human pathogens. Proteus includes pathogens responsible for many human urinary tract infections. P. mirabilis causes wound and urinary tract infections. Most strains of P. mirabilis are sensitive to ampicillin and cephalosporins. P. vulgaris is not sensitive to these antibiotics. However, this organism is isolated less often in the laboratory and usually only targets immunosuppressed individuals. P. vulgaris occurs naturally in the intestines of humans and a wide variety of animals, and in manure, soil, and polluted waters. P. mirabilis, once attached to the urinary tract, infects the kidney more commonly than E. coli. P. mirabilis is often found as a free-living organism in soil and water. About 10–15% of kidney stones are struvite stones, caused by alkalinization of the urine by the action of the urease enzyme (which splits urea into ammonia and carbon dioxide) of Proteus (and other) bacterial species.
This genus contains microbial species that can reside in the human gastrointestinal tract. [PMC 4262072] Straight rods, 0.4–0.8 × 1.0–3.0 μm. Gram negative. Motile by peritrichous flagella. Most strains swarm with periodic cycles of migration producing concentric zones, or spread in a uniform film, over moist surfaces solidified with agar or gelatin. The organisms in this genus conform to the definition of the family Enterobacteriaceae. They are facultatively anaerobic, chemoorganotrophic, having both a respiratory and a fermentative type of metabolism. Optimal growth temperature is 37°C. Oxidase negative; catalase positive. Methyl red positive; species vary in indole production, Voges–Proskauer, and Simmons citrate tests. They oxidatively deaminate phenylalanine and tryptophan. Urea is hydrolyzed. Lysine decarboxylase negative and arginine dihydrolase negative; only Proteus mirabilis decarboxylates ornithine. All but Proteus myxofaciens decompose tyrosine to produce a clearing on agar media in which the insoluble amino acid is incorporated. Grow on KCN. H2S is usually produced. Malonate is not utilized. d-glucose and a few other carbohydrates are catabolized with production of acid and usually gas. Does not produce acid from inositol or from straight chain tetra-, penta-, or hexahydroxy—alcohols, but generally produces acid from glycerol. One or more species ferment maltose, sucrose, trehalose, and d-xylose. Human pathogens, causing urinary tract infections; also are secondary invaders, causing septic lesions at other sites of the body. Occurs in the intestines of humans and a wide variety of animals; also occurs in manure, soil, and polluted waters. P. myxofaciens has been isolated only from gypsy moth larvae. Based on 16S rDNA sequence analysis, Proteus belongs to the family Enterobacteriaceae within the Proteobacteria (Woese et al., 1985; Niebel et al., 1987; Stackebrandt et al., 1988).
The mol% G + C of the DNA is: 38–41 (Falkow et al., 1962).
Type species: Proteus vulgaris