Figure: 09-01 Title: Bacterial Population Growth Curve Caption: Typical bacterial population growth curve showing the initial lag phase, the subsequent log phase where exponential growth occurs, and the stationary phase that occurs when nutrients are exhausted.

Figure: 09-03 Title: Genetic Recombination of Two Auxotrophs Caption: Genetic recombination of two auxotrophic strains producing prototrophs. Neither auxotroph grows on minimal medium, but prototrophs do, suggesting that genetic recombination has occurred.

Figure: 09-04 Title: Davis Experiment Caption: When strain A and B auxotrophs are grown in a common medium but separated by a filter, as in this Davis U-tube apparatus, no genetic recombination occurs and no prototrophs are produced.

Figure: 09-06a Title: F+ X F- Mating Caption: An F+ X F- mating demonstrating how the recipient F- cell converts to F+. During conjugation, the DNA of the F factor replicates with one new copy entering the recipient cell, converting it to F+. The black bars added to the F factor follow their clockwise rotation during replication.

Figure: 09-06b Title: F+ X F- Mating Caption: An F+ X F- mating demonstrating how the recipient F- cell converts to F+. During conjugation, the DNA of the F factor replicates with one new copy entering the recipient cell, converting it to F+. The black bars added to the F factor follow their clockwise rotation during replication.

Figure: 09-07 Title: The Progressive Transfer of Genes During Conjugation Caption: The progressive transfer during conjugation of various genes from a specific Hfr strain of E. coli to an F- strain. Certain genes (azi and ton) transfer more quickly than others and recombine more frequently. Others (lac and gal) take longer to transfer and recombine with a lower frequency.

Figure: 09-08 Title: A Time Map of Gene Transfer Caption: A time map of the genes studied in the experiment depicted in Figure 9-7.

Figure: 09-09 Title: The Order of Gene Transfer in E. coli Caption: (a) The order of gene transfer in four Hfr strains, suggesting that the E. coli chromosome is circular. (b) The point where transfer originates (O) is identified in each strain. Note that transfer proceeds in either direction, depending on the strain. The origin is determined by the point of integration into the chromosome of the F factor, and the direction of transfer is determined by the orientation of the F factor as it integrates.

Figure: 09-10a Title: Conversion of F+ to an Hfr State Caption: Conversion of F+ to an Hfr state occurs by integrating the F factor into the bacterial chromosome. The point of integration determines the origin (O) of transfer. During conjugation, an enzyme nicks the F factor, now integrated into the host chromosome, initiating transfer of the chromosome at that point. Conjugation is usually interrupted prior to complete transfer. Above, only the A and B genes are transferred to the F- cell, which may recombine with the host chromosome.

Figure: 09-10b Title: Conversion of F+ to an Hfr State Caption: Conversion of F+ to an Hfr state occurs by integrating the F factor into the bacterial chromosome. The point of integration determines the origin (O) of transfer. During conjugation, an enzyme nicks the F factor, now integrated into the host chromosome, initiating transfer of the chromosome at that point. Conjugation is usually interrupted prior to complete transfer. Above, only the A and B genes are transferred to the F- cell, which may recombine with the host chromosome.

Figure: 09-11a Title: Conversion of an Hfr Bacterium to F’ Caption: Conversion of an Hfr bacterium to F’ and its subsequent mating with an F- cell. The conversion occurs when the F factor loses its integrated status. During excision from the chromosome, it carries with it one or more chromosomal genes (A and E). Following conjugation with an F- cell, the recipient cell becomes partially diploid and is called a merozygote; it also behaves as an F+ donor cell.

Figure: 09-11b Title: Conversion of an Hfr Bacterium to F’ Caption: Conversion of an Hfr bacterium to F’ and its subsequent mating with an F- cell. The conversion occurs when the F factor loses its integrated status. During excision from the chromosome, it carries with it one or more chromosomal genes (A and E). Following conjugation with an F- cell, the recipient cell becomes partially diploid and is called a merozygote; it also behaves as an F+ donor cell.

Figure: 09-12 Title: A Plasmid of E. coli Caption: (a) Electron micrograph of a plasmid isolated from E. coli. (b) An R plasmid containing resistance transfer factors (RTFs) and multiple r-determinants (Tc, tetracycline; Kan, kanamycin; Sm, streptomycin; Su, sulfonamide; Amp, ampicillin; and Hg, mercury). (Photo: K.G. Murti/Visuals Unlimited)

Figure: 09-13a Title: Proposed Steps for Transforming a Bacterial Cell by Exogenous DNA Caption: Proposed steps for transforming a bacterial cell by exogenous DNA. Only one of the two entering DNA strands is involved in the transformation event, which is completed following cell division.

Figure: 09-13b Title: Proposed Steps for Transforming a Bacterial Cell by Exogenous DNA Caption: Proposed steps for transforming a bacterial cell by exogenous DNA. Only one of the two entering DNA strands is involved in the transformation event, which is completed following cell division.

Figure: 09-14b Title: The Structure of Bacteriophage T4 Caption: The structure of bacteriophage T4 includes an icosahedral head filled with DNA, a tail consisting of a collar, tube, sheath, base plate, and tail fibers. During assembly, the tail components are added to the head and then tail fibers are added.

Figure: 09-15a Title: Life Cycle of Bacteriophage T4 Caption: Life cycle of bacteriophage T4.

Figure: 09-15b Title: Life Cycle of Bacteriophage T4 Caption: Life cycle of bacteriophage T4.

Figure: 09-16a Title: A Plaque Assay for Bacteriophage Analysis Caption: A plaque assay for bacteriophage analysis. Serial dilutions of a bacterial culture infected with bacteriophages are first made. Then three of the dilutions (10-3, 10-5, and 10-7) are analyzed using the plaque assay technique. Each plaque represents the initial infection of one bacterial cell by one bacteriophage. In the 10-3 dilution, so many phages are present that all bacteria are lysed. In the 10-5 dilution, 23 plaques are produced. In the 10-7 dilution, the dilution factor is so great that no phages are present in the 0.1-mL sample, and thus no plaques form. From the 0.1-mL sample of the 10-5 dilution, the original bacteriophage density is calculated to be 23 X 10 X 105 phages/mL (23 X 106, or 2.3 X 107). The photograph shows phage T2 plaques on lawns of E. coli. (Photo: Bruce Iverson)

Figure: 09-16b Title: A Plaque Assay for Bacteriophage Analysis Caption: A plaque assay for bacteriophage analysis. Serial dilutions of a bacterial culture infected with bacteriophages are first made. Then three of the dilutions (10-3, 10-5, and 10-7) are analyzed using the plaque assay technique. Each plaque represents the initial infection of one bacterial cell by one bacteriophage. In the 10-3 dilution, so many phages are present that all bacteria are lysed. In the 10-5 dilution, 23 plaques are produced. In the 10-7 dilution, the dilution factor is so great that no phages are present in the 0.1-mL sample, and thus no plaques form. From the 0.1-mL sample of the 10-5 dilution, the original bacteriophage density is calculated to be 23 X 10 X 105 phages/mL (23 X 106, or 2.3 X 107). The photograph shows phage T2 plaques on lawns of E. coli. (Photo: Bruce Iverson)

Figure: 09-17 Title: The Lederberg-Zinder Experiment Caption: The Lederberg-Zinder experiment using Salmonella. After placing two auxotrophic strains on opposite sides of a Davis U-tube, Lederberg and Zinder recovered prototrophs from the side containing the LA-22 strain but not from the side containing the LA-2 strain. These initial observations led to the discovery of the phenomenon called transduction.

Figure: 09-18a Title: Generalized Transduction Caption: Generalized transduction.

Figure: 09-18b Title: Generalized Transduction Caption: Generalized transduction.

Figure: 09-19 Title: Plaque Morphology Phenotypes Caption: Plaque morphology phenotypes observed following simultaneous infection of E. coli by two strains of phage T2, h+r and hr+. In addition to the parental genotypes, recombinant plaques hr and h+r+ were also recovered. (From Hershey & Chase, 1951)

Figure: 09-UN01 Title: Insights and Solutions Caption: Insights and Solutions question 1

Figure: 09-UN02 Title: Insights and Solutions Caption: Insights and Solutions question 3

Figure: 09-UN03 Title: Problems and Discussion Caption: Problems and Discussion question 32, gene map

Figure: 09-T01 Title: Table 9.1 Caption: Some Mutant Types of T-even Phages

Figure: 09-T02 Title: Table 9.2 Caption: Results of a Cross Involving the h and r Genes in Phage T2 (hr+ X h+r)