How do we know that bacteria undergo genetic recombination, allowing the transfer of genes from one organism to another?

How do we know whether or not genetic recombination between bacteria involves cell-to-cell contact?

In this chapter, we have focused on genetic systems present in bacteria and the viruses that use bacteria as hosts (bacteriophages). In particular, we discussed mechanisms by which bacteria and their phages undergo genetic recombination, the basis of chromosome mapping. Based on your knowledge of these topics, answer several fundamental questions:

How do we know that during transduction bacterial cell-to-cell contact is not essential?

Write a short summary that contrasts how recombination occurs in bacteria and bacteriophages.

Distinguish among the three modes of recombination in bacteria.

With respect to F⁺ and F⁻ bacterial matings, answer the following questions: How was it established that physical contact between cells was necessary?

With respect to F⁺ and F⁻ bacterial matings, answer the following questions: How was it established that chromosome transfer was unidirectional?

With respect to F⁺ and F⁻ bacterial matings, answer the following questions: What is the genetic basis for a bacterium's being F⁺.

List all major differences between:

(a) The F⁺ x F⁻ and the Hfr x F⁻ bacterial crosses

(b) The F⁺, F⁻, Hfr, and F' bacteria.

Describe the basis for chromosome mapping in the Hfr x F⁻ crosses.

Why are the recombinants produced from an Hfr x F⁻ cross rarely, if ever, F⁺?

Describe the origin of F' bacteria and merozygotes.

Describe the mechanism of transformation.

The bacteriophage genome consists of many genes encoding proteins that make up the head, collar, tail, and tail fibers. When these genes are transcribed following phage infection, how are these proteins synthesized, since the phage genome lacks genes essential to ribosome structure?

Describe the temporal sequence of the bacteriophage life cycle.

In the plaque assay, what is the precise origin of a single plaque?

In the plaque assay, exactly what makes up a single plaque?

A plaque assay is performed beginning with 1 mL of a solution containing bacteriophages. This solution is serially diluted three times by combining 0.1 mL of each sequential dilution with 9.9 mL of liquid medium. Then 0.1 mL of the final dilution is plated in the plaque assay and yields 17 plaques. What is the initial density of bacteriophages in the original 1 mL?

Describe the difference between the lytic cycle and lysogeny when bacteriophage infection occurs.

Define plaque, lysogeny, and prophage.

Explain the observations that led Zinder and Lederberg to conclude that the prototrophs recovered in their transduction experiments were not the result of F⁺ mediated conjugation.

Describe the execution of and rationale behind linkage and mapping studies of bacterial genes during transduction experiments.

If a single bacteriophage infects one E. coli cell present on a lawn of bacteria and, upon lysis, yields 200 viable viruses, how many phages will exist in a single plaque if three more lytic cycles occur?

If a single bacteriophage infects one E. coli cell present on a lawn of bacteria and, upon lysis, yields 200 viable viruses, how many phages will exist in a single plaque if three more lytic cycles occur?