Microbiology Unit IV: Antibiotics

The SOS response is a DNA damage response mechanism that is activated when a cell's DNA is damaged. It helps the cell survive by inducing the expression of various genes involved in DNA repair, such as those encoding DNA polymerases and DNA repair enzymes. This activation allows the cell to repair the damaged DNA and maintain genomic integrity. Therefore, the correct answer is that the SOS response activates repressed genes involved in DNA repair.

Ribosomes are responsible for protein synthesis within the cell. They are not involved in mutations or building resistance directly. Therefore, the given answer is incorrect and does not provide a suitable explanation.

Antibiotics that inhibit protein synthesis target bacterial ribosomes, which have a different shape compared to human ribosomes. This difference in shape allows antibiotics to specifically bind to bacterial ribosomes and prevent protein synthesis, while not affecting human ribosomes. Therefore, the inhibition of protein synthesis by antibiotics does not negatively affect humans because our ribosomes are structurally different.

The SOS response is a regulatory mechanism in bacteria that is activated in response to DNA damage. It helps the cell cope with the damage by inducing the expression of genes involved in DNA repair. One step of the SOS response is the generation of DNA repair enzymes, which are proteins that can fix DNA lesions. The other step is the inhibition of cell division or fission, which allows the cell to focus its resources on repairing the DNA instead of dividing. This response is crucial for the survival of bacteria in the presence of DNA damage.

Antibiotic resistance occurs when bacteria undergo natural mutations in their genetic material. These mutations can lead to changes in the bacteria's DNA, allowing them to develop resistance to antibiotics. Over time, these resistant bacteria can multiply and spread, making it more difficult to treat infections. Therefore, the correct answer is natural mutations.

Antibiotics inhibit protein synthesis by binding onto ribosomes. Ribosomes are the cellular structures responsible for protein synthesis. When antibiotics bind onto ribosomes, they interfere with the normal functioning of these structures, preventing them from carrying out their role in protein synthesis. This disruption in protein synthesis can lead to the inhibition of bacterial growth and the elimination of bacterial infections.

The SOS response is a mechanism developed by bacteria when their DNA is injured by antibiotics. This response is a protective mechanism that allows bacteria to repair the damaged DNA and survive in the presence of antibiotics. The SOS response involves the activation of specific genes that are responsible for DNA repair and mutagenesis. By inducing this response, bacteria can increase their chances of survival and develop resistance to antibiotics.

A mutation within a cell can result in changes to the shape of molecules within the cell. In the context of antibiotics, this can lead to a change in the shape of the target molecule that the antibiotic binds to. This change in shape can prevent the antibiotic from effectively binding to its target, reducing its effectiveness in killing or inhibiting the growth of bacteria.

Antibiotic resistance is primarily developed through the production and transfer of plasmids carrying resistant genes. Plasmids are small, circular DNA molecules that can be easily transferred between bacteria. These plasmids often carry genes that provide resistance to antibiotics. When bacteria acquire these plasmids, they gain the ability to survive and multiply in the presence of antibiotics, leading to antibiotic resistance. This transfer of plasmids can occur through processes like conjugation, where bacteria directly exchange genetic material, or through transformation, where bacteria take up free-floating DNA from the environment.

The plasma membrane acts as a barrier that prevents antibiotics from entering the cell. This resistance mechanism occurs at the site of the plasma membrane, where the membrane structure and composition prevent the antibiotics from crossing and reaching their target inside the cell. This mechanism can be a result of mutations in the genes that code for the membrane proteins or enzymes involved in antibiotic uptake, leading to changes in the membrane's permeability and effectively blocking the entry of antibiotics into the cell.

Pumping mechanisms in resistance refer to the ability of certain cells to actively remove antibiotics from their interior. This process allows the cells to maintain a lower concentration of the antibiotic, preventing it from reaching toxic levels and enabling them to survive. By pumping the antibiotic out of the cell, the resistance mechanism ensures that the drug is unable to effectively kill the bacteria, reducing its effectiveness and promoting the survival of resistant strains.

Enzyme production is a method of resistance where bacteria produce enzymes that break down antibiotics through metabolic processes. These enzymes can modify or destroy the antibiotic molecules, rendering them ineffective in killing the bacteria. This mechanism allows the bacteria to survive and continue to multiply, leading to antibiotic resistance. By breaking down the antibiotic, the bacteria can neutralize its effects and evade its intended purpose of killing the bacteria.

The given answer correctly lists the five ways in which antibiotics can take action. Antibiotics can inhibit cell wall synthesis, which weakens the cell walls of bacteria and prevents them from growing and dividing. They can also inhibit protein synthesis, which disrupts the production of essential proteins in bacteria. Additionally, antibiotics can damage the plasma membrane of bacteria, causing their contents to leak out. They can inhibit DNA transcription, which prevents the bacteria from replicating their genetic material. Finally, antibiotics can inhibit enzymes, which are essential for various metabolic processes in bacteria.