Describe the difference between selective and differential media.

The distinction between selective and differential media is rooted in their primary functions and purposes in microbiological applications. Selective media are designed to inhibit the growth of certain bacteria while allowing others to thrive. This selective inhibition is often crucial when isolating a specific organism from a mixed culture. For example, MacConkey agar selects for gram-negative bacteria by inhibiting gram-positive organisms.

On the other hand, differential media are formulated to visually differentiate between species based on their metabolic capabilities or growth characteristics. This differentiation is often achieved through indicators that react with by-products of bacterial metabolism, such as color changes in the medium due to fermentation of sugars. An example of this is blood agar, where hemolytic bacteria produce clear zones around their colonies.

The other options present inaccuracies or misconceptions regarding selective and differential media. While selective media can sometimes be more acidic or might contain specific components like antibiotics, this isn't a definitive characteristic that applies to all selective media. Similarly, while differential media might include certain sugars to facilitate differentiation, it is not correct to say that all differential media must contain sugars. Also, both types of media do not alter bacterial DNA; this occurs through genetic mechanisms unrelated to the media used for culture.