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 Conjugation
   R27 Mutation in     Conjugative       Relative Conjugation
         Region               Transfer                Frequency (%)
             1                          +                            100
             2                          +                            100
             3                          -                               0
             4                         +                             100
             5                         -                                0
             6                         -                                0
             7                         +                              12
             8                         -                                0
             9                         -                                0
           10                         -                                0
           11                         +                              13
           12                         -                                0
           13                         -                                0
           14                         -                                0

Which regions appear to have the most impact on conjugation? 

Key Concepts

Conjugative Transfer

Conjugative transfer is a mechanism of horizontal gene transfer in bacteria, where genetic material, often in the form of plasmids, is transferred from one bacterium to another through direct contact. This process is crucial for the spread of traits such as antibiotic resistance. The tra1 gene in plasmid R27 is specifically involved in facilitating this transfer, making it a key focus in studies of bacterial genetics.

Mutagenesis

Mutagenesis refers to the process of inducing mutations in an organism's DNA, which can help identify the function of specific genes. In the context of the study, particular regions of the tra1 gene were mutated to observe their effects on conjugation efficiency. By analyzing how these mutations impact the transfer frequency, researchers can pinpoint which regions are essential for the conjugative function.

Functional Regions of Genes

Functional regions of genes are specific segments that encode for proteins or regulatory elements necessary for a gene's activity. In the case of the tra1 gene, different regions may have distinct roles in the conjugative transfer process. Understanding which regions are critical for function helps elucidate the mechanisms behind plasmid transfer and can inform strategies to combat antibiotic resistance.