What are parasitic microorganisms that often infect living organisms called?

Parasitic microorganisms that infect living organisms are best described as rickettsiae. Rickettsiae are a group of bacteria that act as parasites and can cause diseases in humans and other animals. They are obligate intracellular pathogens, meaning they can only grow and reproduce within the cells of a host organism. This characteristic is significant because it distinguishes rickettsiae from other types of bacteria, which can often survive outside of a host cell.

Furthermore, rickettsiae are typically transmitted to humans through arthropod vectors, such as ticks, fleas, and lice, which highlights their parasitic nature and the complexities of their life cycle. Understanding rickettsiae is crucial in the study of infectious diseases, as they are responsible for several serious illnesses, like typhus and Rocky Mountain spotted fever, which can have significant health implications if not treated properly.

In contrast, viruses, while they also invade living cells, do not fit the traditional definition of microorganisms as they require a host cell entirely for replication and are not considered living organisms in the same way that rickettsiae are. Bacteria encompass a broad range of microorganisms, some of which can be harmful, but many are free-living and not obligate parasites. F