Problem 1 Two triple auxotrophic strains of E cou: thr- leu- his- pro+ pan+ bio+
ID: 38984 • Letter: P
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Problem 1 Two triple auxotrophic strains of E cou: thr- leu- his- pro+ pan+ bio+ and thr+ leu+ his+ pro- pan- bio-, are allowed to conjugate in a liquid medium for 30 minutes. After dilution of the broth, the bacteria are plated onto a complete (nutrient rich) agar medium in a petri dish, which serves as a master plate from which six replicas are made. Each is plated onto a replica plate containing minimal medium and additional nutrient or nutrients as indicated in the figure. Determine the genotype of each of the six clones Explain how you arrive at the genotype of each.Explanation / Answer
An auxotroph (mutant) is an organism that requires special nutrients in the medium (complete medium) like amino acids as it cannot synthesize them.
A prototroph (wild type) is an organism that can grow even in minimal medium and synthesize the required nutrients for its growth.
A complete medium contains all nutrients that support the growth of organism. An suxotroph requires a complete medium.
A minimal medium is the medium lacking some important nutrients. A wild type or prototroph can grow in a minimal medium.
A master plate contains all the 6 colonies grown on a complete medium. The replica plates contain minimal medium supplemented with the nutrients. The genotypes of the organism in replica plates are given below.
Plate 1: thr - leu - his+ pro+ pan+ bio+
Plate 2: thr+ leu + his+ pro+ pan- bio-
Plate 3 : thr+ leu- his- pro+ pan+ bio+
Plate 4 : thr+ leu + his+ pro- pan- bio+
Plate 5 : thr+ leu + his+ pro- pan+ bio-
Plate 6 : thr- leu + his- pro+ pan- bio-
These genotypes are determined based on the nutrients supplemented to the minimal medium. The nutrients supplemented in the medium are cannot synthesized by the organism hence the organism is indicated with (-) sign. for example, organism cannot synthesize leu means leu- .
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