What does selective media do in microbiological cultures?

Selective media is designed to favor the growth of specific types of microorganisms while inhibiting the growth of others. In this context, the answer highlighting the control of Gram-positive bacteria accompanied by the enhancement of growth for Gram-negative bacteria accurately describes how selective media functions.

Selective media often contains substances that inhibit one group of bacteria while allowing another group to thrive. For instance, specific components can be added to suppress the growth of Gram-positive bacteria, such as bile salts or certain antibiotics, while providing nutrients that support the proliferation of Gram-negative bacteria. This is particularly useful in clinical microbiology to isolate pathogenic Gram-negative organisms from samples where other bacteria are present.

Other options, such as those that suggest encouraging growth of all bacteria or solely isolating viruses, do not accurately represent the targeted purpose of selective media. Yeast growth promotion, while possible with certain media, is outside the primary role of selective media focused on bacteria. Thus, the role of selective media is effectively captured in the correct answer, highlighting its importance in distinguishing and isolating specific bacterial populations for further analysis.