Chapter 6, Problem 29ESP

A study was conducted in an attempt to determine which functional regions of a particular conjugative transfer gene (tral) 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 tral 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 (tral) on R27 Conjugation

1. (a) Given the data, do all functional regions appear to influence conjugative transfer?
2. (b) Which regions appear to have the most impact on conjugation?
3. (c) Which regions appear to have a limited impact on conjugation?
4. (d) What general conclusions might one draw from these data?