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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.
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.
The IMViC tests are a group of individual tests used in microbiology lab testing to identify an organism in the coliform group.A coliform is a gram negative, aerobic, or facultative anaerobic rod, which produces gas from lactose within 48 hours.
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]
E. coli bacteria often carry multiple drug resistance plasmids, and under stress, readily transfer those plasmids to other species. Mixing of species in the intestines allows E. coli to accept and transfer plasmids from and to other bacteria. Thus, E. coli and the other enterobacteria are important reservoirs of transferable antibiotic ...
They are oxidase-positive, catalase-negative, urease-negative, and indole-negative, and reduce nitrate to nitrite. [ citation needed ] In 2006, Azakami et al reported that the periodontal pathogen E. corrodens has an ortholog of luxS , the gene required for quorum sensing (QS) signal molecule AI-2 synthesis and that E. corrodens can produce AI ...
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.
Enterohemorrhagic E. coli (EHEC) Enteroaggregative E. coli (EAEC) Uropathogenic E. coli (UPEC) Verotoxin-producing E. coli; E. coli O157:H7 is an enterohemorrhagic strain also 2006 North American E. coli outbreak; E. coli O104:H4, also 2011 E. coli O104:H4 outbreak; Escherichia coli O121; Escherichia coli O104:H21; Escherichia coli K1, meningitis