Microbial World

Organisms Infectious agents

I Domain B^S^Ta Rua® I Viruses Viroids Prions

Prokaryotes Eukaryotes (unicellular)

Algae Protozoa Fungi Helminths

(unicellular or (unicellular) (unicellular or (multicellular multicellular) multicellular) parasites)

multicellular) parasites)

Protists

Figure 1.10 The Size of a Viroid Compared with a Molecule of DNA from a Virus that Infects Bacteria (T7) The red arrows point to the potato spindle tuber viroids (PSTV); the other arrow points to T7 DNA.

Prions are very unusual agents that are responsible for at least six neurodegenerative diseases in humans and animals; these are always fatal. Prions appear to be only protein, without any nucleic acid (figure 1.11). Although unlikely, it is possible that another agent that is very difficult to isolate might also be involved in causing the neurodegenerative diseases.

Figure 1.11 Prion Prions isolated from the brain of a scrapie-infected hamster. This neurodegenerative disease is caused by a prion.

Bacterial Vaginosis Facts

Bacterial Vaginosis Facts

This fact sheet is designed to provide you with information on Bacterial Vaginosis. Bacterial vaginosis is an abnormal vaginal condition that is characterized by vaginal discharge and results from an overgrowth of atypical bacteria in the vagina.

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