Question

The problem of pathogenic bacteria becoming resistant to a large number of antibiotics is a serious public health concern. A bacterial strain in a paticnt being treated with one antibiotic may suddenly become resistant not only to that antibiotic but to others as well even though it has not been exposed to the other antibiotics. This occurs when the bacteria acquire a plasmid from another strain that contains several different transposons. All of the following phrases describe transposons except A. a means for the permanent incorporation of antibiotic resistance into the bacterial chromosome. B. contain short inverted terminal repeat sequences. C. code for an enzyme that synthesizes guanosine tetraphosphate and guanosine pentaphosphate, which inhibit further transposition. D. include at least one gene that codes for a transposase. E. contain varying numbers of genes.

Short answer

A) A means for the permanent incorporation of antibiotic resistance into the bacterial chromosome. B) Contain short inverted terminal repeat sequences. C) Code for an enzyme that synthesizes guanosine tetraphosphate and guanosine pentaphosphate, which inhibit further transposition. D) Include at least one gene that codes for a transposase. E) Contain varying numbers of genes. Answer: C. Code for an enzyme that synthesizes guanosine tetraphosphate and guanosine pentaphosphate, which inhibit further transposition.

Step-by-step solution

Understanding transposons

Transposons, also known as "jumping genes", are DNA sequences that can move from one location to another on a chromosome or between chromosomes. They play a crucial role in the spread of antibiotic resistance in bacteria by carrying the resistance genes and inserting them into the bacterial genome.

Evaluate each statement

Now, let's examine each statement to find the one that does NOT describe transposons. A. A means for the permanent incorporation of antibiotic resistance into the bacterial chromosome. - True, transposons can carry antibiotic resistance genes and integrate into the bacterial genome, providing a stable inheritance of resistance. B. Contain short inverted terminal repeat sequences. - True, inverted terminal repeat sequences are important for the proper functioning of transposons. C. Code for an enzyme that synthesizes guanosine tetraphosphate and guanosine pentaphosphate, which inhibit further transposition. - False, transposons do not code for this enzyme related to the synthesis of guanosine tetraphosphate and guanosine pentaphosphate. These molecules (ppGpp), also known as the "Stringent response," are involved in the bacterial stress response and regulate gene expression under nutrient-limiting conditions. D. Include at least one gene that codes for a transposase. - True, transposase is an enzyme that helps transposons cut and paste themselves into different locations within the genome. E. Contain varying numbers of genes. - True, transposons can carry different numbers of genes based on their type and size.

Identify the exception

Based on our evaluation, statement C does not correctly describe transposons. It refers to the synthesis of guanosine tetraphosphate and guanosine pentaphosphate, which are part of the bacterial stress response, not related to the transposon. So, the correct answer is: C. Code for an enzyme that synthesizes guanosine tetraphosphate and guanosine pentaphosphate, which inhibit further transposition.

Key concepts

Antibiotic Resistance

Antibiotic resistance is a growing global health problem, where bacteria evolve to resist the effects of medications designed to kill them. This phenomenon can make bacterial infections more difficult, or even impossible, to treat. One of the key ways that bacteria acquire resistance is through genetic changes, which can happen in several ways, such as mutations in their DNA or the acquisition of new DNA material.

Transposons, which are also known as 'jumping genes', are part of this problem. They are DNA sequences that can move from one location to another within the genome of a bacterium. If a transposon carries antibiotic resistance genes, it can transfer these genes between different bacteria, spreading resistance. This is especially concerning when a bacterium that is already resistant to one antibiotic gains a transposon that confers resistance to additional antibiotics.

Antibiotic resistance genes can thus be shared among bacterial populations through mechanisms like conjugation, transformation, and transduction. The former involves direct cell-to-cell contact to transfer genetic material, often plasmids or transposons, between bacteria, while the latter two involve the uptake of free DNA from the environment and bacterial viruses (bacteriophages), respectively. Each method contributes to the propagation of resistance, turning previously treatable diseases into serious health threats.

Bacterial Genetics

Understanding bacterial genetics is crucial to comprehend how these single-celled organisms can rapidly adapt to environmental changes, including the presence of antibiotics. Bacteria have a simple genetic structure, consisting mainly of a single circular chromosome. However, they also possess additional small circles of DNA known as plasmids. Plasmids often carry beneficial genes that can be transferred between bacteria, a process known as horizontal gene transfer.

In addition to plasmids, transposons play a significant role in bacterial evolution and diversity. These mobile genetic elements can disrupt or alter genetic sequences, contribute to genetic recombination, and even cause mutations. The ability of transposons to move within a genome and potentially between bacteria via plasmids or other methods means they are a powerful force in the genetic reshuffling that can lead to new traits, such as antibiotic resistance.

Bacteria benefit from a high mutation rate and mechanisms like transformation, transduction, and conjugation to exchange genetic material. In the face of selective pressures such as antibiotic use, these capabilities allow them to quickly evolve resistance. Therefore, understanding bacterial genetics provides insight into how to manage and prevent the spread of antibiotic resistance.

DNA Sequences

DNA sequences are the fundamental instructions within a cell that dictate everything from the synthesis of proteins to the regulation of metabolic pathways. In bacteria, DNA sequences within their chromosomes, plasmids, and transposable elements such as transposons, dictate the bacteria's characteristics, including their ability to resist antibiotics.

Transposons are categorized based on their DNA structure and the method they use to 'jump'. Their structure typically includes a gene that encodes a transposase enzyme, which facilitates the cutting and pasting of the transposon into new locations. Furthermore, they may carry additional genes, including those conferring antibiotic resistance, which can be potentially passed to other bacteria.

The structure of transposons often includes short sequences known as inverted terminal repeats, essential for transposase recognition. These repeats flank the transposon and signal where the transposase should cut to mobilize the transposon to a new site. It is through these mechanisms that transposons contribute to the plasticity of bacterial genomes and play a major part in the spread of antibiotic resistance, which is a critical issue in contemporary medicine.