Final answer:
The term 'sterile' refers to the zone where no bacterial growth occurs due to the presence of an antimicrobial drug. A chemically modified antimicrobial derived from a natural compound is termed semisynthetic. Oxygenic photosynthesis produces oxygen and can be performed by bacteria, while eutrophication results from excessive nutrient-induced microbial growth in water.
Step-by-step explanation:
The Zone of Inhibition and Microbial Control
The zone mentioned in the student's question refers to the zone of inhibition, which is an area of no bacterial growth around an antimicrobial-impregnated filter disk in a culture. When bacteria are killed in this zone, it is described as being sterile. This term is used to indicate that the bacteria have been eradicated and no living organisms are present in that zone.
Antimicrobial Properties of Soil Bacteria
A scientist studying soil bacteria that produce an antimicrobial able to kill gram-negative bacteria made a chemical modification to it, enabling it to also kill gram-positive bacteria. This modified drug is considered semisynthetic because it has been partly produced by chemical synthesis to improve its efficacy.
Photosynthetic Bacteria and Eutrophication
Photosynthesis performed by bacteria using water as an electron donor is described as oxygenic. This is because it leads to the production of oxygen. Additionally, the process in which oxygen levels are depleted in aquatic systems due to overgrowth of microorganisms from excess nutrients is known as eutrophication.
Microbial Control Protocols
To control microbial growth specifically targeting molds and yeast, a fungistatic approach is used, which inhibits their growth rather than killing them outright. For a total kill strategy, a fungicidal method would be employed.