Associate Certified Entomologist (ACE) Practice Exam

What is the source of macrocyclic lactones?

1. Plant extracts

2. Soil bacterium

3. Chemical synthesis

4. Animal byproducts

The correct answer is: Soil bacterium

The source of macrocyclic lactones is indeed derived from soil bacterium, specifically from the genus Streptomyces. This group of bacteria produces these compounds as secondary metabolites. Macrocyclic lactones, such as ivermectin, are widely utilized in veterinary and medical applications, particularly for their antiparasitic properties. Soil bacterium plays a significant role in the natural production of these compounds, and due to their efficacy against various parasites, they have been harnessed for therapeutic use. The mechanism by which macrocyclic lactones operate involves the modulation of neurotransmission in parasites, leading to paralysis and death of the organisms. In contrast, the other options do not pertain to the natural source of macrocyclic lactones. Plant extracts may contain various bioactive compounds but are not the origin of macrocyclic lactones. Chemical synthesis can produce similar compounds, but it does not reflect their natural source. Animal byproducts do not provide the necessary materials for the creation of macrocyclic lactones as derived from soil bacteria.