A round-shaped microorganism that stains a red color is a?

The identification of a round-shaped microorganism that stains red is indicative of Gram-negative cocci. In the Gram staining process, microorganisms are classified based on their cell wall structure and how they react to the staining procedure.

Gram-negative bacteria, which include cocci, possess a thinner peptidoglycan layer and an outer membrane that contains lipopolysaccharides. This structural difference causes them to retain the red counterstain (typically safranin) used in the Gram staining process. Therefore, if a microorganism appears red after the staining, it indicates that it is indeed Gram-negative.

In the case of cocci, these are spherical-shaped bacteria, and when stained, they present as red-colored entities under the microscope. This is a key characteristic used in microbiology to identify the type of bacteria present.

Gram-positive cocci, on the other hand, would stain purple due to their thick peptidoglycan layer retaining the crystal violet stain. Bacilli, whether Gram-positive or Gram-negative, refer to rod-shaped bacteria, and thus do not fit the description given in the question. Understanding these fundamental principles of Gram staining provides clarity on identifying and categorizing microorganisms effectively.