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 a limited impact on conjugation? <>

Key Concepts

Conjugative Transfer

Conjugative transfer is a process by which one bacterium transfers genetic material to another through direct contact. This mechanism often involves plasmids, which are small, circular DNA molecules that can carry genes, including those for antibiotic resistance. Understanding this process is crucial for analyzing how genes, such as tra1, facilitate the transfer of plasmids like R27 in bacteria.

Gene Mutation Analysis

Gene mutation analysis involves systematically altering specific regions of a gene to observe the effects on its function. In the context of the tra1 gene, mutations can help identify which regions are essential for conjugative transfer by comparing the conjugation frequency of mutated strains to that of the wild type. This method is fundamental in pinpointing functional regions critical for gene activity.

Antibiotic Resistance

Antibiotic resistance refers to the ability of bacteria to survive and proliferate despite the presence of antibiotics that would normally inhibit their growth. The R27 plasmid is significant because it encodes multiple antibiotic resistance genes, making it a public health concern. Understanding the genetic mechanisms behind this resistance is vital for developing strategies to combat resistant bacterial strains.