Question

Which one of the following statements concerning plasmids is true? A. All plasmids can be transfered between bacteria by conjugation. B. Much of the information coded in the plasmid is essential to the survival of the bacteria cell. C. Resistance plasmids carry genes for antibiotic resistance. D. Resistance plasmids cannot be transferred to other bacterial cells. E. Plasmids lack an origin of replication.

Short answer

The correct statement is 'C. Resistance plasmids carry genes for antibiotic resistance.'

Step-by-step solution

Eliminate the Incorrect Options

Let's start by eliminating the untrue statements. Option A states that all plasmids can be transferred between bacteria by conjugation. However, this is not the case. The ability to be transferred is specific to conjugative plasmids. Option B is also incorrect, since the genetic information in plasmids usually isn't essential for basic bacterial survival. Option D suggests that resistance plasmids can't be transferred - this is false. The transfer of resistance plasmids to other bacterial cells is a contributing factor to antibiotic resistance. Option E is incorrect too, as plasmids do contain an origin of replication, which enables them to be independently copied within the bacterial cell.

Identify the Correct Option

Once the untrue options are discounted, the correct answer is clear. Option (C) states that 'Resistance plasmids carry genes for antibiotic resistance.' This is indeed true. Resistance plasmids (or R plasmids) carry genes that confer resistance to antibiotics, making the bacteria capable of surviving and growing in the presence of specific antibiotics.

Key concepts

Conjugation in Bacteria

Conjugation is a fascinating process in bacteria, which allows them to transfer genetic material. It's like bacterial communication through the sharing of DNA. This process is vital for genetic diversity and can occur when one bacterium, carrying a plasmid with conjugative capability, connects to another through a structure called a pilus.
The pilus is a bit like a tiny bridge between two bacteria. It enables the genetic material within a plasmid to transfer from one bacterium to another. However, not all plasmids can be shared this way.

• Only plasmids with specific sequences known as the "tra" genes can facilitate this transfer.
• These are known as "conjugative plasmids."
• Non-conjugative plasmids require help from conjugative ones to move between cells.

Understanding conjugation is crucial, as it’s a significant mechanism by which bacteria can gain new traits, such as antibiotic resistance.

Antibiotic Resistance

Antibiotic resistance is a critical issue in modern medicine. It occurs when bacteria evolve to withstand the effects of antibiotics, making infections harder to treat. One of the main culprits behind this phenomenon is the transfer of resistance plasmids.
These plasmids are small, circular DNA molecules that often carry several resistant genes.

• Resistance plasmids allow bacteria to survive the presence of antibiotics.
• When shared through processes like conjugation, these plasmids spread resistance to other bacteria.
• This can result in "superbugs," or bacterial strains resistant to multiple antibiotics.

As a result, managing antibiotic resistance is a priority in healthcare, requiring responsible antibiotic prescription and innovative treatments.

Origin of Replication

The origin of replication is a crucial component of plasmids. It’s a specific sequence of DNA that signals the start site for DNA synthesis. This region is what enables plasmids to replicate independently inside bacterial cells.
Here's how it works:

• The replication origin attracts enzymes necessary for DNA duplication processes.
• Once the enzymes bind, the plasmid DNA unwinds and starts copying itself.
• This enables the plasmid to be passed down to future generations of bacteria.

Understanding the origin of replication is vital because it underpins how plasmids, like resistance plasmids, can multiply and consequently, how traits such as antibiotic resistance persist and spread within bacterial populations.