Look closely at the consolidated Hfr map and the data used to build the map on page 261. Suppose a fifth Hfr strain had the F factor inserted exactly halfway between cysE and leuU and had an orientation that was the same as that of Hfr 1. List the order of gene transfer for the first six genes transferred by this Hfr and the number of minutes of conjugation at which each gene is expected to be seen.

An Hfr strain is used to map three genes in an interrupted mating experiment. The cross is Hfr/a⁺b⁺c⁺ rif x F⁻/a⁻b⁻c⁻ rif^T (No map order is implied in the listing of the alleles; rif^T is resistance to the antibiotic rifampicin.) The a⁺ gene is required for the biosynthesis of nutrient A, the b⁺ gene for nutrient B, and c⁺ for nutrient C. The minus alleles are auxotrophs for these nutrients. The cross is initiated at time = 0 and at various times, the mating mixture is plated on three types of medium. Each plate contains minimal medium (MM) plus rifampicin plus specific supplements that are indicated in the following table. (The results for each time interval are shown as the number of colonies growing on each plate.)Time of Interruption _5 min 10 min 15 min 20 minNutrients A and B 0 0 4 21 Nutrients B and C 0 5 23 40 Nutrients A and C 4 25 60 82Can the location of the rif gene be determined in this experiment? If not, design an experiment to determine the location of rif relative to the F factor and to gene b.

An Hfr strain is used to map three genes in an interrupted mating experiment. The cross is Hfr/a⁺b⁺c⁺ rif x F⁻/a⁻b⁻c⁻ rif^T (No map order is implied in the listing of the alleles; rif^T is resistance to the antibiotic rifampicin.) The a⁺ gene is required for the biosynthesis of nutrient A, the b⁺ gene for nutrient B, and c⁺ for nutrient C. The minus alleles are auxotrophs for these nutrients. The cross is initiated at time = 0 and at various times, the mating mixture is plated on three types of medium. Each plate contains minimal medium (MM) plus rifampicin plus specific supplements that are indicated in the following table. (The results for each time interval are shown as the number of colonies growing on each plate.)Time of Interruption _5 min 10 min 15 min 20 minNutrients A and B 0 0 4 21 Nutrients B and C 0 5 23 40 Nutrients A and C 4 25 60 82Based on these data, determine the approximate location on the chromosome of the a, b, and c genes relative to one another and to the F factor.

An Hfr strain is used to map three genes in an interrupted mating experiment. The cross is Hfr/a⁺b⁺c⁺ rif x F⁻/a⁻b⁻c⁻ rif^T (No map order is implied in the listing of the alleles; rif^T is resistance to the antibiotic rifampicin.) The a⁺ gene is required for the biosynthesis of nutrient A, the b⁺ gene for nutrient B, and c⁺ for nutrient C. The minus alleles are auxotrophs for these nutrients. The cross is initiated at time = 0 and at various times, the mating mixture is plated on three types of medium. Each plate contains minimal medium (MM) plus rifampicin plus specific supplements that are indicated in the following table. (The results for each time interval are shown as the number of colonies growing on each plate.)Time of Interruption _5 min 10 min 15 min 20 minNutrients A and B 0 0 4 21 Nutrients B and C 0 5 23 40 Nutrients A and C 4 25 60 82What is the purpose of rifampicin in the experiment?

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.Donor _Recipient E. chrysanthemi E. blattae E. fergusonii E. coliE. chrysanthemi -2.4 -4.7 -5.8 -3.7E. blattae -2.0 -3.4 -5.2 -3.4 E. fergusonii -3.4 -5.0 -5.8 -4.2E. coli -1.7 -3.7 -5.3 -3.5What is the significance of these findings in terms of human health?

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.Donor _Recipient E. chrysanthemi E. blattae E. fergusonii E. coliE. chrysanthemi -2.4 -4.7 -5.8 -3.7E. blattae -2.0 -3.4 -5.2 -3.4 E. fergusonii -3.4 -5.0 -5.8 -4.2E. coli -1.7 -3.7 -5.3 -3.5In what species is within-species transfer most likely? In what species pair is between-species transfer most likely?

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.Donor _Recipient E. chrysanthemi E. blattae E. fergusonii E. coliE. chrysanthemi -2.4 -4.7 -5.8 -3.7E. blattae -2.0 -3.4 -5.2 -3.4 E. fergusonii -3.4 -5.0 -5.8 -4.2E. coli -1.7 -3.7 -5.3 -3.5What general conclusion(s) can be drawn from these data?

A study was conducted in an attempt to determine which functional regions of a particular conjugative transfer gene (tra1) are involved in the transfer of plasmid R27 in Salmonella enterica. The R27 plasmid is of significant clinical interest because it is capable of encoding multiple-antibiotic resistance to typhoid fever. To identify functional regions responsible for conjugal transfer, an analysis by Lawley et al. [(2002). J. Bacteriol. 184:2173–2180] was conducted in which particular regions of the tra1 gene were mutated and tested for their impact on conjugation. Shown here is a map of the regions tested and believed to be involved in conjugative transfer of the plasmid. Similar coloring indicates related function. Numbers correspond to each functional region subjected to mutation analysis.Accompanying the map is a table showing the effects of these mutations on R27 conjugation.Effects of Mutations in Functional Regions of Transfer Region 1 (tra1) on R27 ConjugationR27 Mutation in Conjugative Relative Conjugation Region Transfer Frequency (%)1 + 1002 + 1003 - 04 + 1005 - 06 - 07 + 128 - 09 - 010 - 011 + 1312 - 013 - 014 - 0Given the data, do all functional regions appear to influence conjugative transfer?