Notes:
1) Prokaryotes divided into two domains which are bacteria and archaea.
2) Definition of prokaryote: Organisms that lack a cell nucleus or any other membrane-bound organelles.
3) They are unicellular, but a few prokaryotes such as myxobacteria have multicellular stages in their life cycles.
4) Prokaryotic diversity include proteobacteria, cyanobacteria, gram positive bacteria, spirochetes with unique morphology, green sulfur and green nonsulfur bacteria.
- Proteobacteria are a major group (phylum) of gram-negative bacteria.
a. Alphaproteobacteria - They grow at very low nutrient area and are agriculturally important because they able to induce nitrogen fixation.
b. Epsilonproteobacteria - They are microaerophilic and they are the most common cause in stomach cancer.
c. Gammaproteobacteria - They are medically important and a large group of pathogen belong to this group such as Salmonella spp.
d. Betaproteobacteria - They play a role in nitrogen fixation in various types of plants, oxidizing ammonium to produce nitrite.
e. Deltaproteobacteia - They are predators on other bacteria and are important contributors to the sulfur cycle.
- Cyanobacteria are aquatic and photosynthesic. They have live on earth for 3.5 billion years. Therefore, they important in shaping the course of evolution and ecological change throughout earth's history.
- Gram positive bacteria have specifc membrane structure. Their structure consist of thick peptidoglycan layer, teichoic acids and gram-positive bacteria are more receptive to antibiotics than gram-negative, due to the absence of the outer membrane.
- Spirochetes are helical in shape They are tightly coiled, and so look like miniature springs or telephone cords.These filaments run along the outside of the protoplasm, but inside an outer sheath; they enable the bacterium to move by rotating in place. Spirochetes causes syphilis and lyme disease.
- Green sulfur bacteria and green nonsulfur bacteria are autotrophs. They produce energy from light and are named for their green pigment, usually found in photosynthetic bodies called chlorosomes.
- Deinococcus radiodurans are extremophilic bacteria where they can survive cold, dehydration, vacuum and acid. Deinococcus radiodurans has a unique quality in which it can repair both single- and double-stranded DNA. When a damage is apparent to the cell, it brings it into a compartmental ring-like structure, where the DNA is repaired and then is able to fuse the nucleoids from the outside of the compartment with the damaged DNA. They are the toughest bacterium in the world.
5) Archaea, the another domain of prokaryote. They are known as extremophiles, halophiles and thermoacidophiles. Their can survice in harsd environement because of their specific cell structure. They are chemotrophic and chemolithotrophics. The example of archaea is Pyrolobus and Halobacterium.
The differences between Bacteria and Archaea:
My own Explorace:
1) Deinococcus radiodurans can withstand large amounts of radiation, can live in a vacuum for up to six weeks and live, can live dehydrated, and live through fluctuations in pH. This bacteria is so special that it was the first be in the phylum "Deinococcus". This is one of the only organisms in the world that can withstand 5,000 GYs of radiation. It can repair itself completely within 12-24 hours and can survive on Mars.
2) Crenarchaeota are Archaea that have been classified as a phylum of the Archaea kingdom.The Crenarchaeota were thought to be sulfur-dependent extremophiles but recent studies have identified characteristic Crenarchaeota environmental rRNA indicating the organism may be the most abundant archaea in the marine environment. Until recently all cultured Crenarchaea had been thermophilic or hyperthermophilic organisms, some of which have the ability to grow at up to 113 °C. These organisms stain Gram negative and are morphologically diverse having rod, cocci, filamentous and oddly shaped cells.
3) E. coli O157:H7’s ability to induce injury in humans is a result of its ability to produce numerous virulence factors, most notably Shiga toxin, which is one of the most potent toxins known to man.
4) Shiga toxin has multiple variants and acts like the plant toxin ricin by inhibiting protein synthesis in endothelial and other cells. Endothelial cells line the interior surface of blood vessels, and are known to be extremely sensitive to E. coli O157:H7, which is cytotoxigenic to these cells.
Reflection:
Deinococcus radiodurans are such a strong bacteria, I can't imagine how they can withstand so high radiation that even can't stand by a person. This is my first time heard proteobacteria in the class. Proteobacteria are gram negative bacteria but it has divided into five classes.
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