What type of microorganisms includes agents that can cause serious environmental infections in humans?

Fungi are a diverse group of microorganisms that include yeasts, molds, and mushrooms. Some fungi play significant roles in the environment, such as contributing to nutrient cycling and decomposition, but certain species can also be pathogenic and lead to serious infections in humans, particularly those with compromised immune systems.

Environmental fungi like Aspergillus, Candida, and Cryptococcus have been known to cause serious health issues, including respiratory infections and systemic diseases. For instance, Aspergillus can lead to invasive aspergillosis, particularly in individuals with weakened immune responses, such as those undergoing chemotherapy or organ transplantation.

In contrast to fungi, while protozoa and bacteria can also be pathogenic, many of their infections are primarily tied to specific environmental conditions or contaminated sources. Rickettsias are a type of bacteria specifically associated with arthropod vectors and are less commonly responsible for serious environmental infections compared to fungi. Thus, fungi stand out as a major group of microorganisms that can cause significant infections stemming from environmental exposure.