Use the following information to answer questions 1 and 2. Two culture media were inoculated with four different bacteria. After incubation, the following results were obtained:
<IMAGE>


Medium 1 is
a. selective.
b. differential.
c. both selective and differential.

Verified step by step guidance

1. Understand the definitions: A selective medium allows the growth of certain types of organisms, while inhibiting the growth of others. A differential medium allows multiple types of organisms to grow, but they will display visible differences (such as color changes) based on their metabolic activities.
2. Examine the results from the image provided (not visible here) to determine if only certain bacteria grew on Medium 1. If only specific bacteria grew, it suggests that the medium is selective.
3. Check if the bacteria that grew on Medium 1 showed any visible differences, such as color changes or different colony morphologies. If so, this indicates that the medium is differential.
4. Consider if Medium 1 could be both selective and differential. This would mean it allows only certain bacteria to grow and also shows visible differences among those that do grow.
5. Based on the observations from the image, decide if Medium 1 is selective, differential, or both, by applying the definitions and characteristics of selective and differential media.

Key Concepts

Selective Media

Selective media are designed to favor the growth of specific microorganisms while inhibiting the growth of others. This is achieved through the inclusion of certain chemicals or conditions that create an environment conducive to the target organisms. For example, a medium containing antibiotics will allow only antibiotic-resistant bacteria to grow.

Differential Media

Differential media allow multiple types of microorganisms to grow but contain indicators that reveal differences between them. These indicators can be pH indicators or substrates that certain bacteria can metabolize, leading to visible changes in the medium. For instance, a medium that changes color in the presence of acid produced by fermenting bacteria is considered differential.

Both Selective and Differential Media

Some media serve both selective and differential purposes, allowing specific bacteria to grow while also providing a means to distinguish between them based on their metabolic activities. An example is MacConkey agar, which selects for Gram-negative bacteria and differentiates them based on lactose fermentation, indicated by color changes in the medium.