MICR 221 Lecture Notes - Lecture 6: Facultative Anaerobic Organism, Obligate Anaerobe, Auxotrophy
13 Jul 2017
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An auxotroph is a bacterium that is unable to synthesize a compound. If the following auxotrophs were plated onto a growth medium containing arginine, lactose, and ampicillin, which would survive: arg-, lac+, ampr, arg+, lac-, ampr, arg-, lac+, amps, arg-, lac-, amps. Ans: a: an arg- auxotroph is unable to synthesize the amino acid arginine. Facultative anaerobes: use oxygen when it"s around - but they don"t need it -- these bacteria are. Tolerant anaerobes: can grow in the presence/ absence of oxygen , but do not use it in their metabolism. Obligate anaerobes: poisoned by oxygen -- oxygen is bad for them. Obligate anaerobes lack certain enzymes necessary for the detoxification of free radicals. These free radicals spontaneously form whenever oxygen is present. Question 1: if a bacterium cannot use oxygen as electron acceptor-- It could be either an obligate or tolerant anaerobe depending on the its ability to neutralize harmful oxygen free radicals.
