You are watching: Many bacteria that are able to metabolize citrate produce negative results in this test why
the complete agar (CM) key are provided to inspect for the substance"s toxicity. If the zone that inhibition is greater on the CM+ test substance plate than the centimeter + DMSO plate, the problem is toxic to bacteria.
which plates do you must examine in order to recognize if your test substance is mutagenic? what is her conclusion around your test substance?
the minimal agar key (MM) are supplied to inspect for substance"s mutagenicity. If the variety of colonies top top the MM+ check substance is greater than the number ~ above the MM + DSMO plate, the substance is taken into consideration mutagenic to bacteria.
if the test substance includes protein, it will contain histidine, which will be provided by histidine auxotrophs ~ above the minimal medium. The auxotrophs will grow and also it will show up the substance is mutagenic i m sorry it may not yes, really be
the auxotrophs need to thrive in order for them to mutate. A small amount of histidine is contained in the tool so they grow for a few generations and also get exposed come the doubt mutagen. If they dont""t mutate, lock stop growing when the histidine is gone. If they carry out mutate, they continue growing
why are the small colonies on the MM plates not considered back mutants? why dont they grow the complete size?
these space the auxotrophs that flourished while the minimal medium still had the original, small amount that histidine. Castle didn"t continue growing as soon as the histidine was exhausted because they didn"t mutate into histidine prototrophs
what room some benefits of the Ames test over carcinogen tests utilizing rats or mice? What space some disadvantages?
advantages: fast results, simple to keep the speculative organisms, and huge numbers the organisms deserve to be subjected to the suspected mutagen. Disadvantages: the check is not done ~ above a mammalian system, some products are only mutagenic after modification in the mammalian host, toxicity that the substance to the bacteria reduces efficiency of the test
For a provided antibiotic, is there a difference in susceptibility between the Gram + and Gram - bacteria?
yes- antibiotics that influence the peptidoglycan the the cell wall (i.e- penicillin) are more effective against Gram + cells because of their better abundance the peptidoglycan
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