The bad guys. Everything that causes disease is considered a pathogen. We can split pathogens into two categories cellular (living) and non cellular (non-
Bacteria (click here for more info)
Bacteria are prokaryotes, thus they are simple, single celled organisms. They are found pretty much everywhere and replicate rapidly via binary fission (click for more information). The majority of bacteria in the world actually play a very important role in the ecosystem.
Irritation can be caused by the toxins the produce, interfering with cellular processes. Bacteria may also release enzymes which break down our cells and tissue.
Viruses
Viroids
Prions
Protozoa are unicellular organisms, however unlike bacteria they are Eukaryotes. This means they have membrane bound organelles and are much more complex than bacteria.
We can break pathogenic protozoa into 3 categories:
- Flagellates
- Sporozoans
- Sarcodinians
Fungi are extremely important pathogens. In humans they cause tinea, ringworm and thrush.
Some fungi can actually kill insects. Spores which land on the skin of fly, grow and eventually kill it.
The 3 main groups of fungi which cause injury to humans are:
- Mould
- True yeast
- Fungi-
like yeast
Parasitic worms are very common throughout the environment. Some of the common parasitic worms include:
- Flatworms
- Round worms
Technically non cellular pathogens are not living. This is because viruses, Viroids and prions can not replicate outside of a host cell and thus don’t meet the requirements for ‘living’.
Viruses can infect all types of organisms, from prokaryotic bacteria to Eukarytoic human cells.
They are refereed to as obligate intracellular parasites (can’t replicate outside of a host cell).
Viruses, although simple in design are actually very complex.
Viroids are similar to viruses however much simpler and smaller ( 1/10 the size of the smallest virus) in design. Unlike a virus they don’t have a protein coat, or any other enzymes. They are simply a single stranded circular piece of RNA.
Prions are just proteins. However they cause massive amounts of damage in an organism. They are made of miss formed PrP (prion Protein).