These organisms can be free-living or can be found in the gut of animals.
The type of cells which do not have a well-defined nucleus and no membrane-bound organelles are known as prokaryotic cells. Organisms with prokaryotic cells are called prokaryotes and they are generally single-celled microorganisms. These organisms can be free-living or can be found in the gut of animals. The size of a prokaryotic cell can range between 0.2 to 10 microns. Examples of prokaryotic cells include bacterial cells, which have different shapes and structures and possess extrachromosomal DNA known as a plasmid. Archaeal cells which are similar to bacterial cells, are found in extreme environments such as hot springs and also in soil and marsh. These single-celled organisms also possess plasmids.
Prokaryotic cells are not complex structures. They do not have a true nucleus and the genetic material is not contained within a membrane but it is seen as coiled in the cytoplasm of the cell. Below is a list of structures that can be observed in a prokaryotic cell.
Major Components of The Prokaryotic Cell:
All bacterias are prokaryotes and the above-mentioned structures can be seen in all bacterial cells. Prokaryotic cellular organisms or prokaryotes can be divided into two domains:
Reproduction in a prokaryotic cell takes place in two ways Binary fission: The process starts with the replication of the DNA molecule and two copies of the molecule attach themselves to the cell membrane.
Recombination: The genes of one cell are transferred to the genome of another cell. The process takes place in three ways
A prokaryotic cell can be defined as a cell which does not have a well-defined nucleus or membrane-bound organelles such as mitochondria or and lysosomes. An organism with a prokaryotic cell is called a prokaryote and they are generally bacterias. Although most bacteria cause diseases some are beneficial. The function of these prokaryotic cells are: Digestion of food: Bacteria such as lactobacillus help in the digestion of lactose in the stomach Inhibition of pathogens: Gut flora also plays a role in defending our body against pathogens. Development of enteric protection: The gut flora (bacteria) is established in the first two years of birth. After it is established, the intestinal lining also establishes and in a way gut bacteria against pathogens which can enter into the stomach through food.
Probiotics are live bacteria that are good for the human digestive system. The function of probiotics is to replenish gut flora after an infection. Some common probiotics are Lactobacillus and Bifidobacterium. Probiotics can be used for the treatment of infectious diarrhoea, inflammatory bowel syndrome, and irritable bowel syndrome.
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Archaea can be subdivided into
Euryarchaeota: Eg: Haloarchaea
Crenarchaeota: Acidilobus saccharovoran
Nanoarchaeota: Nanoarchaeum equitans
Bacteria can be subdivided into Proteobacteria- eg: Rhizobium Chlamydias- eg: Chlamydia trachomatis Spirochetes: Treponema pallidum (Syphilis causing bacteria) Cyanobacteria: Prochlorococcus Gram-positive bacteria: Bacillus anthracis (Anthrax causing bacteria) Gram-negative bacteria: Salmonella typhi (typhoid causing bacteria)