Question

A scientist discovers that a soil bacterium he has been studying produces an antimicrobial that kills gramnegative bacteria. She isolates and purifies the antimicrobial compound, then chemically converts a chemical side chain to a hydroxyl group. When she tests the antimicrobial properties of this new version, she finds that this antimicrobial drug can now also kill gram- positive bacteria. The new antimicrobial drug with broad-spectrum activity is considered to be which of the following? a. resistant b. semisynthetic c. synthetic d. natural

Short answer

The new antimicrobial drug with broad-spectrum activity is considered to be semisynthetic.

Step-by-step solution

Understanding the Scenario

The scenario describes a soil bacterium producing an antimicrobial that is effective against gram-negative bacteria. The scientist then modifies the compound by converting a chemical side chain into a hydroxyl group. After modification, the antibiotic also becomes effective against gram-positive bacteria.

Identifying the Antimicrobial Drug Type

The modified antimicrobial drug, effective against a broader range of bacteria, is made through human intervention to change its chemical structure. This type of drug is neither completely synthetically made nor entirely natural because it is chemically altered from its original, natural form.

Choosing the Correct Option

Based on the information provided, the correct answer is 'semisynthetic'. This term applies to drugs that are naturally occurring but have been chemically modified to enhance their efficacy or spectrum of activity.

Key concepts

Antimicrobial Activity

Antimicrobial activity refers to the process by which substances inhibit the growth of or destroy harmful microorganisms, like bacteria and fungi. In the context of the exercise, the soil bacterium being studied produces a substance that naturally possesses these properties towards gram-negative bacteria. By chemically modifying the compound, the scientist aims to enhance the substance's efficacy.

Antimicrobials can be broad-spectrum, targeting a wide variety of bacteria, or narrow-spectrum, designed to attack specific types. In this case, the modification of the compound from the soil bacterium extends its activity from solely affecting gram-negative bacteria to also targeting gram-positive bacteria, making it broad-spectrum.

Understanding how antimicrobial drugs work is pivotal, as it allows scientists to modify existing compounds to combat a wider range of pathogens. This flexibility is particularly important in the face of antibiotic resistance, where bacteria evolve to become less susceptible to conventional drugs.

Gram-Negative Bacteria

Gram-negative bacteria are characterized by their unique cell wall structure, which includes a thin layer of peptidoglycan and an outer membrane. This outer membrane is composed of lipopolysaccharides and acts as a protective barrier, often making gram-negative bacteria more resistant to antibiotics than gram-positive bacteria.

The original soil bacterium-derived antimicrobial attacked these gram-negative bacteria effectively. However, one of the biggest challenges in treating infections from gram-negative bacteria is their resistance to many common antibiotics. This is why the development of new or modified antimicrobials, like in the exercise example, is of such great significance.

Students should remember that the gram-negative classification is based on the Gram stain test, which is a fundamental laboratory procedure to categorize bacteria based on their cell wall characteristics.

Gram-Positive Bacteria

Gram-positive bacteria, while still different from their gram-negative counterparts, also have a distinctive cell wall structure, consisting of a thick peptidoglycan layer that lacks the outer membrane present in gram-negative bacteria. This feature makes them stain differently during the Gram stain test and is one of the factors that affect their interaction with antimicrobials.

The scientist's modification of the soil bacterium antibiotic to possess a hydroxyl group improved its ability to target and kill these gram-positive bacteria. This highlights the significance of understanding cellular structures when developing new antimicrobial drugs and how slight chemical modifications can lead to significant changes in drug efficacy.

Students studying these concepts can appreciate the innovation in pharmaceutical development that arises from such molecular-level tweaks, allowing the treatment of a broader range of bacterial infections.