Usually prokaryotes are unicellular (but not always). Although microbes are commonly unicellular, these grow in colony and some types of bacteria can form biofilm that enhances their survival.
Note: word “cyto” – refers to “cell”, a word originated from Greek. (Dictionarycom.)
Here are the basic cell components of prokaryotes:
All cells have: (also found in Eukaryotes)
- Cell Wall (not found in animal cell)
- This is rigid strong outer layer that protects cell from osmosis (bursting) and supports the cell by maintaining the shape.
- In prokaryotes, it is often made out of peptidoglycan
- In eukaryotes, (fungi, plants) it is often made out of cellulose
- Cytoplasmic membrane/plasma membrane/cell membrane
- This is a barrier that separates the inside of the cell from the outside of the cell.
- Function is to control what nutrients can enter/exit the cell. This can serve to protect cell from harmful substances like antibiotics.
- This is aqueous mixture containing macromolecules, ions, proteins, ribosomes etc. that fills the dead space inside the cell.
- Molecules found in cytoplasm are essential for efficient metabolism.
- These are found within cytoplasm, and is the site of protein synthesis.
Components only specific to prokaryotes
- Nucleoid region
- Randomly/irregular shaped region in cytosol/cytoplasm of prokaryotic cell housing DNA. There is no membrane. It is an open region where various enzymes, RNA and proteins are found for cellular metabolism.
- Note that no nucleus membrane is what allows mRNA and protein synthesis to occur at the same time for some prokaryotes.
- This is a piece of DNA that carries non-essential (often) or sometimes essential genes. For example, it could be genes for antibiotic resistance.
- Flagellum (exception, found in protozoan (euk.)
- This is long microtubule structure that allows cell to move
- Proteinaceous and multi-subunit structure. (kline et al., 2010)
- These are used to attach to surfaces/epithelial cells/other cells (biofilm), an important virulence factor for an infection in many microbes. (Schilling et al., 2001)
- Outer membrane (only found in Gram negative bacteria) (Brown et al., 2015)
- It contains lipopolysaccharides (LPS) and various porins/efflux pump, transporters which confer bacteria with antibiotic resistance.
- LPS is large polymer that have three parts: lipid A, core oligosaccharide and O-antigen. (Gu et al., 2015)
- Detailed structure drawing: Peptidoglycan structure and function
- Periplasmic space (in Gram negative bacteria)
- This is a region between cell membrane and outer membrane of cell
- There are various enzymes for hydrolysis, chemoreceptors and binding proteins. This space is also where transportation, degradation and motility is carried out.
Brown, L., Wolf, J. M., Prados-Rosales, R. and Casadevall, A. Nat. Rev. Microbiol. (2015) 13: p. 620-630.
Cell Functions. Cell Functions. (http://www.biologyjunction.com/cell_functions.htm) (accessed Feb. 2, 2017).
cyto-. Dictionarycom. Dictionary.com. (http://www.dictionary.com/browse/cyto-) (accessed Feb. 2, 2017).
Gu, Y., Stansfeld, P. J., Zeng, Y., Dong, H., Wang, W. and Dong, C. Structure. (2015) 23 (3): p. 496-504.
Kline, K. A., Dodson, K. W., Caparon, M. G. and Hultgren, S. J. Trends. Microbiol. (2010) 18(5): p. 224-232.
-24 The periplasm is between the cytoplasmic and outer membranes in gram-negative bacteria. Through the Microscope Main News RSS. (http://www.microbiologytext.com/5th_ed/book/displayarticle/aid/59) (accessed Feb 2, 2017″.
Schilling, J. D., Mulvey, M. A. and Hultgren, S. J. Jou. Infect. Dis. (2001) 183 (Supplement 1): p. 36-40.