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The genome of Pseudomonas aeruginosa consists of a relatively large circular chromosome (5.5–6.8 Mb) that carries between 5,500 and 6,000 open reading frames, and sometimes plasmids of various sizes depending on the strain. [11] Comparison of 389 genomes from different P. aeruginosa strains showed that just 17.5% is shared.
It is designed to selectively isolate gram-negative and enteric (normally found in the intestinal tract) bacteria and differentiate them based on lactose fermentation. [1] Lactose fermenters turn red or pink on MacConkey agar, and nonfermenters do not change color. The media inhibits growth of gram-positive organisms with crystal violet and ...
Other enterobacteria such as E. coli will ferment the lactose present in the medium to an extent that will prevent pH reversion by decarboxylation and acidify the medium, turning it yellow. Salmonella species: red colonies, some with black centers. The agar itself will turn red due to the presence of Salmonella type colonies.
Pseudomonas species also typically give a positive result to the oxidase test, the absence of gas formation from glucose, glucose is oxidised in oxidation/fermentation test using Hugh and Leifson O/F test, beta hemolytic (on blood agar), indole negative, methyl red negative, Voges–Proskauer test negative, and citrate positive. [citation needed]
Non-fermenters (also non-fermenting bacteria) are a taxonomically heterogeneous group of bacteria of the phylum Pseudomonadota that cannot catabolize glucose, and are thus unable to ferment. This does not necessarily exclude that species can catabolize other sugars or have anaerobiosis like fermenting bacteria.
Hektoen enteric agar (HEK, HE or HEA) is a selective and differential agar [1] primarily used to recover Salmonella and Shigella from patient specimens. HEA contains indicators of lactose fermentation and hydrogen sulfide production; as well as inhibitors to prevent the growth of Gram-positive bacteria.
TSI agar slant results: (from left) preinoculated (as control), P. aeruginosa, E. coli, Salmonella Typhimurium, Shigella flexneri The Triple Sugar Iron (TSI) test is a microbiological test roughly named for its ability to test a microorganism's ability to ferment sugars and to produce hydrogen sulfide. [1]
Shigella sonnei can ferment lactose, but only after prolonged incubation, so it is referred to as a late-lactose fermenter. During fermentation of the sugar, acid is formed and the pH of the medium drops, changing the color of the pH indicator. Different formulations use different indicators; neutral red is often used. For example, lactose ...