In a conjugation experiment, we used two strains: Hfr: streptomycin sensitive and F-: auxotrophic for isoleucine and threonine, streptomycin resistant. If we interrupt conjugation when only threonine gene has been transferred and spread this mixture on: Minimal media, Minimal media with streptomycin Minimal media with threonine and streptomycin Minimal media with isoleucine and streptomycin LB agar plates with streptomycin On which plates do we expect bacterial growth? Why?

In a conjugation experiment, we used two strains: Hfr: streptomycin sensitive and F-: auxotrophic for isoleucine and threonine, streptomycin resistant. If we interrupt conjugation when only threonine gene has been transferred and spread this mixture on: Minimal media, Minimal media with streptomycin Minimal media with threonine and streptomycin Minimal media with isoleucine and streptomycin LB agar plates with streptomycin On which plates do we expect bacterial growth? Why?

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter17: Bacterial And Viral Genetics

Section: Chapter Questions

Problem 1ITD

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Two auxotrophic triple Escherichia coli strains (A: met- phe- ade- val+ bio+ thr+ and B: met+ phe+ ade+ val- bio- thr-) are mixed in LB liquid medium, diluted and then spread on LB solid rich medium. Six colonies are observed: Then, replicates are performed on 6 different media (minimum medium + glucose + indicated substances). The results are shown below. Determine the genotype of the 6 colonies observed. Which ones are from strain A? From strain B? Which hypotheses can explain these results and which one do you prefer? met phe val bio Abbreviations: met ade val thr phe ade bio thr Met: methionine; Phe: phenylalanine; Ade: adenine; Val: valine; Bio: biotin; Thr: threonine.
Given what we've discussed in class, what will be most likely outcome if you conjugate an streptomycin resistant ampicillin sensitive methionine auxotroph E. coli strain (engineered to be pir+) that is F- with a streptomycin sensitive non-HFR methionine prototroph strain that is F- and RP4+ but contains pUC18? Colonies on minimal media + ampicillin +streptomycin plates No colonies on minimal media +ampicillin +streptomycin plates
Draw a diagram/figure to explain the conjugation process (e.g. use PowerPoint or draw one by hand and include a photo of it). You should include in the diagram the F- recipient, Hfr Donor and the transconjugant/recombinant recipient. Make sure to include the genes encoding for Leucine, Threonine, Thiamine and Streptomycin resistance in your diagram. How does an Hfr strain of coli transfers chromosomal DNA to an F- strain? What determines how much of the chromosomal DNA is transferred?
Draw a diagram/figure to explain the conjugation process (. You should include in the diagram the F- recipient, Hfr Donor and the transconjugant/recombinant recipient. Make sure to include the genes encoding for Leucine, Threonine, Thiamine and Streptomycin resistance in your diagram. How does an Hfr strain of coli transfers chromosomal DNA to an F- strain? What determines how much of the chromosomal DNA is transferred?
Three pairs of bacterial cells with the given genotypes undergo conjugation. Place match the genotype of each cell after conjugation to its initial genotype. F+ x F Hfr F- F' F- Answer Bank F F F+ Hfr What is the role of the F-factor in conjugation? It contains genes necessary for replication of the donor's F plasmid. can occur. It allows auxotrophic bacterial cells to survive on minimal medium so that conjugation It contains genes that force recombination between the donor and recipient chromosomes. It contains genes necessary for the formation of the pilus. O It degrades the chromosome of the recipient cell after conjugation.
The following two strains of E. coli are crossed with each other: Hfr pan* thi* ala* and F¯pan¯ thi¯ ala¯ It was shown that the pan marker entered last in interrupted conjugation experiments. By spreading the bacteria from these experiments on different selection media, the following results (in number of colonies) were obtained: MM + Gluc IM + Gluc + ala MM + Gluc + thi MM + Gluc + thi + ala 280 281 286 339 Give the number of each phenotypic class and justify your answer. Determine the order of the genes. What are the genetic distances between the different loci? Abbreviations: Gluc: glucose; Ala: alanine; Thi: thiamine; Pan: pantothenic acid.
You have conducted a transposon mutagenesis experiment using the same PRL27 system that was used during your lab exercise. After allowing for conjugation. you plate the conjugation mix on Luria agar and Luria + Kanamycin agar. After incubation, you count the following number of colonies on each type of plate: Media Dilution Number of Colonies Too Many to Luria 10-5 Count 10-6 173 10-7 28 Luria + Kanamycin 100 324 10-1 217 10-2 3 Determine the transformation efficiency. Note: You can enter you answer using long form (e.g. 1500000) or scientific notation using e notation (e.g. 1.5e6). Do not enter units.
Conjugation depends on direct cell-to-cell contactbetween a donor F+ carrying either a conjugative________ (the F plasmid) or an integrated conjugativeelement (as in Hfr strains), and a recipient lacking suchan element (F−).
An Hfr strain that is hisE+ and pheA+ was mixed with a strain thatis hisE− and pheA−. The conjugation was interrupted and the percentageof recombinants for each gene was determined by streakingon a medium that lacked either histidine or phenylalanine. Thefollowing results were obtained:It was found that hisE is 4 minutes away from pabB. The gene pheA was shown to be 17 minutes from pabB. Draw a genetic map describing the locations of all three genes.
A prototrophic strain (his" arg" lac') was used as a donor to transform an auxotrophic strain (his arg lac'). Initial transformants are isolated on minimal medium + histidine + arginine + lactose - glucose. i. What genotypes will grow on this medium? ii. These colonies are replicated to minimal medium + histidine, and 50% of the original colonies grow. What genotypes will grow on this medium? iii. The original colonies are also replicated to minimal medium + arginine, and 10% of the colonies grow. What genotypes will grow on this medium? iv. The original colonies are also replicated to minimal medium. No colonies grow. Based on this information, what genotypes will grow on minimal medium + histidine and on minimal medium + arginine? What is the relative gene order for his, arg, and lac? Which two genes are closer? Explain your answer.
The figure below shows a partial chromosome map of an E. coli Hfr strain. Each mark = 10 minutes between conjugation transfer time. If transfer of genes begins at “*” relative to the origin of transfer, what is one of the predicted results from this map? It would take less than 30 minutes to transfer all of the genes that are shown. gal and azi will rarely be transferred together. gal and ton will rarely be transferred together. Ten minutes after transfer of ton, lac will be transferred. This strain will produce very few gal recombinants.
A high cell density culture of recombinant E. coli was carried out according to the following strategy:-Step 1: single batch with exponential growth until 98% conversion of the substrate, starting from V0= 4.0 L, S0=50 g/L/ X0= 1.0 g/LStep 2: batch fed with exponential flow (SF-800 g/L, μ= 0.1 h-1) until reaching X= 50.9 g/L;Step 3: batch fed with constant flow (F= 0.1 L/h) for 4 hours (induction phase with IPTG)Note: consider that the quasi-steady state is reached in both fed-batch stages.Extra data: YX/S = 0.4 gx/gs; μmax= 0.25 h-1; Ks== 1.0 g/L a) What was the cell concentration reached at the end of step 1?b) For step 3, considering that the substrate concentration in the feed was 1/4 of that used in step 2, what was the concentration of cells reached at the end of step 3?C) In terms of cell productivity, which of the three phases of cultivation was the most productive?