PathogensA pathogen is any organism that is the direct cause of a disease.
There are for main types of pathogens:
VirusesA pathogen that consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopically, and is able to multiply only within the living cells of a host. Viruses are known to infect nearly every type of organism on earth, even bacteria and are considered neither prokaryotic or eukaryotic.
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All Germs aren't Bad!Want to learn more? Watch the video below!
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Reproduction: Viruses cannot reproduce without the help of another living cell, or a host cell. Once a virus has infected a cell, it can insert its genetic material into the cell. Since viruses cannot eat food, they take materials by hijacking cellular machinery, taking over the cell's functions. Sometimes, a virus will stay dormant in the cell for long periods of time. This is known as the lysogenic phase. When a virus is found outside of a cell, the virus has a protein coating called a capsid.
Viruses are a common cause of disease in humans. Smallpox, the common cold, chickenpox, influenza, shingles, herpes, polio, rabies, ebola, and AIDS are examples of viral diseases.
Viruses are a common cause of disease in humans. Smallpox, the common cold, chickenpox, influenza, shingles, herpes, polio, rabies, ebola, and AIDS are examples of viral diseases.
BacteriaBacteria are typically 100 times larger than viruses. They consist of a ring of DNA surrounded by cellular machinery. Some bacteria live and multiply in an environment, while others require a host.
Reproduction: Bacteria reproduce by dividing into two. Some bacteria can double in number every fifteen minutes, while others can take weeks or even months to grow. Bacteria causes many types of diseases, from severe pneumonia to a mild skin rash, as well as tissue damaging conditions such as gangrene. However, disease is not the only way they present themselves to us - the 'smell of rain' is actually caused by bacteria called Actinomycetes. |
PARASITESParasites are part of a large group of organisms called eukaryotes. Parasites are different from bacteria or viruses because their cells share many features with human cells including a defined nucleus. Parasites are usually larger than bacteria, although some environmentally resistant forms are nearly as small.
Reproduction: Some parasites only replicate within a host organism, but many can multiply freely in the environment. Parasites can be made of one cell, as is the case with Giardia, or many cells, as is the case with parasitic worms. |
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Great videos to watch on the many different kinds of parasites!
FungiFungi are diverse in terms of their shape, size and means of infecting humans. Fungi are eukaryotes, meaning that like parasites, their cells have a true nucleus and complex internal structures.
Reproduction: They are most commonly found as environmentally resistant spores and molds, but can cause disease in humans in the form of yeasts. Fungi most often cause skin infections and pneumonia. Fungal diseases are particularly dangerous to immunocompromised people, such as those suffering from AIDS. |