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 was conducted 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 Conjugation

Which regions appear to have the most impact on conjugation? 

Verified step by step guidance

1. Step 1: Examine the map of the tra1 gene regions and note the color coding, which groups regions by related function. This helps to understand which functional groups might be involved in conjugation.
2. Step 2: Review the table showing the effects of mutations in each region on conjugative transfer frequency. Pay attention to whether the mutation results in a '+' (positive transfer) or '-' (negative transfer) and the corresponding relative conjugation frequency percentage.
3. Step 3: Identify regions where mutations cause a complete loss of conjugation (0% relative conjugation frequency). These regions are critical for conjugation function.
4. Step 4: Compare regions with partial reduction in conjugation frequency (e.g., 12% or 13%) to those with no effect (100%) to determine which regions have a significant but not complete impact on conjugation.
5. Step 5: Conclude that regions with 0% conjugation frequency upon mutation have the most impact on conjugation, indicating these regions are essential for the transfer of the R27 plasmid.

Key Concepts

Conjugative Transfer and Plasmids

Conjugative transfer is a process where genetic material, typically plasmids, is transferred between bacteria through direct contact. Plasmids like R27 carry genes that can confer antibiotic resistance, making their transfer clinically significant. Understanding which gene regions control this transfer helps in combating the spread of resistance.

Functional Regions of Genes and Mutation Analysis

Genes often contain multiple functional regions responsible for different activities. Mutation analysis involves altering specific regions to observe changes in function, helping identify which parts are essential. In this study, mutating regions of the tra1 gene revealed which areas are critical for plasmid conjugation.

Interpreting Conjugation Frequency Data

Conjugation frequency measures how effectively a plasmid is transferred between bacteria. A relative frequency of 100% indicates normal transfer, while 0% means no transfer. By comparing frequencies after mutations, researchers can pinpoint which gene regions are vital for conjugation, as seen with regions showing 0% frequency.