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.

What is the significance of these findings in terms of human health?

Verified step by step guidance

1. Step 1: Understand the data presented in the table. The values are log base 10 rates of plasmid transfer between different Escherichia species, where a value like -2.0 corresponds to a transfer rate of 10⁻². Lower (more negative) values indicate lower transfer rates, and higher (less negative) values indicate higher transfer rates.
2. Step 2: Analyze the pattern of plasmid transfer rates between species. Notice which donor-recipient pairs have higher transfer rates (values closer to zero) and which have lower rates (more negative values). This will help identify how easily plasmids can move between different species.
3. Step 3: Consider the biological significance of plasmid transfer. Since plasmids often carry genes for antibiotic resistance or pathogenicity, higher rates of transfer between species suggest a greater potential for spreading these traits across bacterial populations in the human body.
4. Step 4: Relate the findings to human health. Given that many bacterial species coexist in the human gut and skin, the ability of plasmids to transfer between species means that antibiotic resistance or virulence factors can spread more widely, potentially complicating treatment of infections.
5. Step 5: Summarize the overall significance. The data indicate that conjugative plasmids can transfer between different Escherichia species at varying rates, highlighting the risk of horizontal gene transfer contributing to the spread of antibiotic resistance and pathogenic traits in human-associated bacterial communities.

Key Concepts

Bacterial Conjugation and Plasmid Transfer

Bacterial conjugation is a process where genetic material, often plasmids, is transferred directly between bacteria through cell-to-cell contact. Conjugative plasmids like the F plasmid carry genes that can include antibiotic resistance or virulence factors, enabling rapid spread of these traits across bacterial populations.

Logarithmic Scale in Measuring Transfer Rates

The rates of plasmid transfer are expressed as log base 10 values, where a value of -2 means a transfer rate of 10⁻². This logarithmic scale allows comparison of very small transfer rates, highlighting significant differences in conjugation efficiency between species pairs.

Implications for Human Health and Microbiome

Since diverse bacterial species coexist in the human gut and skin, the ability of plasmids to transfer between species facilitates the spread of antibiotic resistance and pathogenic traits. This interspecies gene transfer poses a health risk by potentially creating multidrug-resistant or more virulent bacterial strains.