Question

By what means do bacterial cells acquire new DNA? a. by conjugation, the mating of two cells of the same bacterial species b. by transduction, the injection of viral DNA into bacterial cells c. by transformation, the uptake of DNA from the environment d. by all of the above e. by none of the above

Short answer

The correct answer is option D: by all of the above. Bacterial cells can acquire new DNA through conjugation, transduction, and transformation.

Step-by-step solution

Understanding option A

Option A explains that bacterial cells can acquire new DNA through conjugation - a method where two cells of the same bacterial species mate. This is a correct statement as new DNA can be traded between the two cells during this process.

Understanding option B

Option B points out that bacterial cells can gain new DNA through transduction - a process where bacteriophages (viruses that invade bacterial cells) transfer viral DNA into bacterial cells. This statement is also true.

Understanding option C

Option C suggests that bacterial cells can take up DNA from their environment, a process known as transformation. This is another true statement.

Final Assessment

Having established that all options A, B, and C are correct methods in which bacterial cells can acquire new DNA, the correct answer must be option D 'by all of the above'.

Key concepts

Conjugation

Conjugation is one of the primary ways bacterial cells exchange genetic material. In this process, two bacterial cells, typically of the same species, come together. They form a direct connection through a structure known as a pilus. This connection facilitates the transfer of genetic material, usually in the form of plasmids. Plasmids are small, circular DNA molecules that are separate from the chromosomal DNA.

The role of conjugation is crucial in the spread of antibiotic resistance among bacteria. This occurs because plasmids often carry genes that confer resistance to antibiotics. Consequently, when bacteria acquire these plasmids from neighboring cells, they gain new abilities, such as surviving antibiotic treatments.

Conjugation has an important role in bacterial adaptation and evolution. It enables the rapid spread of advantageous genes through bacterial populations. Given these traits, understanding conjugation is essential for researchers working on microbial genetics and antibiotic resistance issues.

Transduction

Transduction involves the transfer of genetic material from one bacterium to another via a bacteriophage. Bacteriophages, often referred to as phages, are viruses that infect bacteria.

In transduction, a phage infects a bacterial cell and incorporates pieces of the bacterial DNA into its viral DNA. When the phage goes on to infect another bacterial cell, it can introduce the original host's DNA into the new cell. This accidental transfer of bacterial DNA allows for genetic variation within bacterial populations.

There are two primary forms of transduction: generalized and specialized. Generalized transduction occurs when random pieces of bacterial DNA are packaged into phage particles. Specialized transduction involves specific pieces of bacterial DNA being transferred, often near the phage's integration site within the host genome.

Transduction plays a significant role in bacterial evolution by enabling the spread of genes across different strains and species, leading to genetic diversity.

DNA Acquisition in Bacteria

Bacteria have several methods to acquire new DNA, which contribute to their genetic diversity and adaptability in various environments. Apart from the well-known processes of conjugation and transduction, bacteria also partake in transformation.

In transformation, bacterial cells pick up naked DNA molecules from their environment. This DNA may come from dead and lysed bacteria. Once inside, this acquired DNA may recombine with the bacterial chromosome, leading to genetic variation.

These processes—conjugation, transduction, and transformation—are critical to bacterial survival. They allow bacteria to adapt to environmental stresses and contribute to the emergence of traits like pathogenicity and antibiotic resistance.

• Conjugation enables horizontal gene transfer through direct cell-to-cell contact.
• Transduction transfers genetic material using bacteriophages.
• Transformation involves uptake of free DNA from the environment.

Understanding these processes provides insight into microbial dynamics and offers avenues for combating antibiotic-resistant bacteria.