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E. coli is a gram-negative, facultative anaerobe, nonsporulating coliform bacterium. [18] Cells are typically rod-shaped, and are about 2.0 μm long and 0.25–1.0 μm in diameter, with a cell volume of 0.6–0.7 μm 3. [19] [20] [21] E. coli stains gram-negative because its cell wall is composed of a thin peptidoglycan layer and an outer membrane.
Indole test positive: appearance of pink layer at top (e.g. Escherichia coli) Like many biochemical tests on bacteria, results of an indole test are indicated by a change in color following a reaction with an added reagent. Pure bacterial culture must be grown in sterile tryptophan or peptone broth for 24–48 hours before performing the test.
In addition, it is indole test-positive, meaning that this organism can split tryptophan to indole, pyruvate, and ammonia. M. morganii also produces urease, allowing it to break down urea. [9] Methyl red tests positive in M. morganii, an indicator dye that turns red due to the bacterium's acid production during fermentation. [7]
If E. coli bacteria escape the intestinal tract through a perforation (for example from an ulcer, a ruptured appendix, or due to a surgical error) and enter the abdomen, they usually cause peritonitis that can be fatal without prompt treatment. However, E. coli are extremely sensitive to such antibiotics as streptomycin or gentamicin.
The identification of E. corrodens may be delayed because of its slow growth in the absence of CO 2. [16] E. corrodens can be treated with penicillins, cephalosporins, or tetracyclines, however due to the resistant nature of the bacteria ongoing and recurring symptoms can be expected despite rigorous and prolonged antibiotic treatment. [17]
The species C. amalonaticus, C. koseri, and C. freundii can use citrate as a sole carbon source. Citrobacter species are differentiated by their ability to convert tryptophan to indole (C. koseri is the only citrobacter to be commonly indole-positive), ferment lactose (C. koseri is a lactose fermentor), and use malonate.
They are oxidase-negative, catalase-positive, indole-negative, nonmotile, and usually nitrate-negative. [citation needed] Bacteria of the genus Acinetobacter are known to form intracellular inclusions of polyhydroxyalkanoates under certain environmental conditions (e.g. lack of elements such as phosphorus, nitrogen, or oxygen combined with an ...
The organisms causing endogenous infections are generally gram negative bacilli such as Enterobacteriaceae (i.e. Escherichia coli, Klebsiella pneumoniae, Proteus spp. ), and Pseudomonas aeruginosa. Exposure to higher doses of radiation is associated with systemic anaerobic infections due to gram negative bacilli and gram positive cocci. Fungal ...