Bacterial conjugation, mediated mainly by conjugative plasmids such as F, represents a potential health threat through the sharing of genes for pathogenicity or antibiotic resistance. Given that more than 400 different species of bacteria coinhabit a healthy human gut and more than 200 coinhabit human skin, Francisco Dionisio [(2002) Genetics 162:1525 1532] investigated the ability of plasmids to undergo between-species conjugal transfer. The following data are presented for various species of the enterobacterial genus Escherichia. The data are presented as 'log base 10' values; for example, -2.0 would be equivalent to 10⁻² as a rate of transfer. Assume that all differences between values presented are statistically significant.
In what species is within-species transfer most likely? In what species pair is between-species transfer most likely?

Question

Bacterial conjugation, mediated mainly by conjugative plasmids such as F, represents a potential health threat through the sharing of genes for pathogenicity or antibiotic resistance. Given that more than 400 different species of bacteria coinhabit a healthy human gut and more than 200 coinhabit human skin, Francisco Dionisio [(2002) Genetics 162:1525 1532] investigated the ability of plasmids to undergo between-species conjugal transfer. The following data are presented for various species of the enterobacterial genus Escherichia. The data are presented as 'log base 10' values; for example, -2.0 would be equivalent to 10⁻² as a rate of transfer. Assume that all differences between values presented are statistically significant.
Table showing log base 10 rates of plasmid transfer between four Escherichia species, with highest transfer from E. coli to E. chrysanthemi.

In what species is within-species transfer most likely? In what species pair is between-species transfer most likely?

Table showing log base 10 rates of plasmid transfer between four Escherichia species, with highest transfer from E. coli to E. chrysanthemi.

In what species is within-species transfer most likely? In what species pair is between-species transfer most likely?

Accepted Answer

Hello everyone and welcome to today's video. So in an interrupted mating experiment between a donor and a recipient bacterium, we can determine which of the following. Now, before we jump into this problem, I really want to hope you recall what the purpose of this interrupted mate the experiment is going to be and the main purpose is to map the order of donor genes located in a chromosome entering the recipient cell. So remember that during conjugation there is going to be genes from the donor cell entering the recipient cell. Now we can determine the order of these genes in the chromosome by looking at how they are entering this recipient cell. Now let's go over each of our answer choices so that we may solve this problem. Beginning by answer choice. The gene order of the f minus bacterial chromosome. Now they remember that this F minus lacks the F. Plasmid. So it is not going to be a donor. Instead it is going to be a recipient. So we cannot really use this interrupted meeting experience experiment to determine the order of its genes. So we're going to cancel this out. Then we have B the genome size of the H. F. R bacteria. Remember that we're looking for the order nor the size of the genome. So we're going to cancel it out as well. Then we have the the physical distance between genes on the f minus bacterial chromosome. Now remember that we already canceled the possibility of using the F minus in answer choice A. So we're going to cancel it here again. And finally we have seen the gene order on the H f R bacterial chromosome. Now remember that this H f r contains the F plasma in the chromosome and it is going to be able to act as a donor cell Because of this. We're going to be able to use interrupted mating experiments to determine the order of the H f. R bacterial chromosome when it is engaged in conjugation. Because of this answer choice C. Is going to be the correct answer to a question. I really hope this video helped you and I hope to see you on the next one.

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Key Concepts

Bacterial Conjugation and Plasmid Transfer

Logarithmic Scale in Measuring Transfer Rates

Species-Specificity in Plasmid Transfer