Final answer:
Bacteriostasis is the mechanism inhibiting bacterial growth on solid mediums, visible as a zone of inhibition around an antibiotic disk in tests like the Kirby-Bauer assay. A fungistatic agent inhibits fungal growth, and quorum quenching disrupts bacterial communication, potentially serving as a sustainable disease control method. Semisynthetic drugs are chemically modified natural antibiotics with broad-spectrum activity.
Step-by-step explanation:
The mechanism by which the growth of colonies on a solid medium is inhibited is known as bacteriostasis when referring to bacteria. When a substance, such as an antibiotic, prevents bacterial growth without killing the bacteria, it is exhibiting a bacteriostatic effect. The process of bacteriostasis is often observable in laboratory testing, such as the Kirby-Bauer disk diffusion test. This test measures the zone of inhibition around an antibiotic disk to determine the susceptibility of bacteria to the antibiotic.
Addressing question 4, the microbial control protocol that inhibits the growth of molds and yeasts without killing them is termed fungistatic. In contrast, fungicidal refers to substances that kill fungi outright.
For question B, quorum quenching is a strategy that targets the bacterial communication mechanism known as quorum sensing. Bacteria use quorum sensing to determine their population density and to coordinate certain behaviors, including virulence factor production and biofilm formation. Quorum quenching disrupts these signals, potentially serving as a sustainable method of disease control by reducing the selective pressure on bacteria to develop antimicrobial resistance.
Regarding question 6, the term that refers to the specificity of an antimicrobial drug harming the microbe without affecting the host is known as therapeutic index, which was not among the provided options. The correct term in a broader context would be selective toxicity.
In context to the question on a new antimicrobial drug, such a product is considered semisynthetic if it originates from a natural source and is then chemically modified to enhance its efficacy against a broader range of bacteria.
During the log phase or exponential growth phase (question 3), antibiotics like penicillin, which inhibit cell-wall synthesis, are most effective. This is due to the active division and cell-wall synthesis occurring in bacteria at this stage.