Which of the following is not a characteristic of anaerobic cocci?

Anaerobic cocci are microorganisms that thrive in environments devoid of oxygen. One notable characteristic of many anaerobic cocci is that they are generally catalase-negative, rather than catalase-positive. Catalase is an enzyme that breaks down hydrogen peroxide into water and oxygen, and organisms that are catalase-negative lack this enzyme, making them more susceptible to oxidative stress that can arise from reactive oxygen species.

These anaerobic cocci can indeed be part of the normal flora in human microbiota, commonly found in the gastrointestinal tract, mouth, and other mucosal surfaces, contributing to the microbial community that exists in these areas. They are also known to be involved in opportunistic infections, particularly in cases where they gain access to normally sterile sites due to disruptions, such as surgical wounds or abscesses. Furthermore, anaerobic cocci can be either gram-positive or gram-negative, which presents further diversity in this group of bacteria.

Therefore, the assertion that they are generally catalase-positive contrasts with their common biochemical traits, particularly among those that are well-studied, which is why it is the correct answer to the question regarding which characteristic does not apply to anaerobic cocci.