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

Key Concepts

Bacterial Conjugation

Bacterial conjugation is a process of horizontal gene transfer where 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 for traits such as antibiotic resistance. Understanding this process is crucial for analyzing how bacteria can share harmful traits, impacting public health.

Conjugative Plasmids

Conjugative plasmids, such as the F plasmid, are specialized plasmids that facilitate the transfer of genetic material between bacteria during conjugation. They contain genes that encode the machinery necessary for the formation of a pilus, which connects donor and recipient cells. The ability of these plasmids to move between different bacterial species is significant for the spread of antibiotic resistance and pathogenicity.

Logarithmic Data Representation

The data presented in logarithmic form (log base 10) allows for easier comparison of rates of gene transfer between different bacterial species. A negative log value indicates a lower transfer rate, with the magnitude reflecting the rate's significance. Understanding this representation is essential for interpreting the results of the study and drawing valid conclusions about the efficiency of gene transfer among the tested species.