Notes:
1) The intracellular structure found in prokaryote are plasma membrane, cytoplasm, the nuclear area, ribosomes, inclusions and endospore.
- Plasma membrane
- Function: selectively permeable barrier, synthesize cell wall components, assists in DNA replication, carries on respiration and captures energy as ATP.
- The movement of materials across membrane: simple diffusion, facilitated diffusion, osmosis, active transport and group translocation.
- Simple diffusion, facilitated diffusion and osmosis do not require energy where active transport and group translocation belong to active transport.
- Group translocation are molecules that chemically modified during passage across cytoplasmic membane.
- Cytoplasm
- Cytoplasm refers to the substance of the cell inside the plasma membrane,
- contains proteins, carbohydrates, lipids, inorganic ions, DNA, ribosomes and inclusions.
- lacks of cyoskeleton
- The nuclear area
- Single long circular molecule of double-stranded DNA
- do not include histones and not surrounded by nuclear envelope
- In addition to the bacterial chromosome, bacteria often contain small circular, double stranded DNA molecule called plasmid.
- Plasmid
- small circular, double stranded DNA
- do not contain genetic material essential for growth
- contain features that enhance survivability such as gene for drug resistance can be transfer from one bacterial to another
- The characteristic of plasmid: not connected to bacterial chromosome and replicate independently of chromosomal DNA
- Ribosomes
- for protein synthesis
- 70S ribosome
- small subunit - 30S and large subunit - 50S
- Each subunit consists of protein and RNA called ribosomal RNA ot rRNA.
- Cells that have high rates of protein synthesis, have a large number of ribosomes.
- Inclusions
- divided into granules and vesicles
- Metachromatic granules are large inclusion. Volutin granules are an intracytoplasmic (inside the cytoplasm of a cell) storage form of complexed inorganic polyphosphate, the production of which is used as one of the identifying criteria when attempting to isolate Corynebacterium diphtheriae on Löffler's medium. They appear red when stained with methylene blue and gives a metachromatic effect.
- Sulfur granules serve a an energy reserve, derive energy by oxidising sulfur and sulfur-containing compounds. The bacteria that contain sulfur granules is sulfur bacteria.
- Carboxysomes contain the enzyme ribulose 1,5 - diphosphate carboxylase. It used for carbon dioxide fixation during photosynthesis.
- Magnetosomes contain iron oxide that act like magnets. Their main function is to protect the cell against hydrogen peroxide accumulation.
- Lipid inclusions store polymer poly-beta-hydroxybutric acid. It revealed by Sudan eyes and the example of bacteria that contain lipid inclusion is Mycobacterium, Bacillus, Azotobacter and Sprillum.
- Gas vesicles are normally found in photosynthetic group such as cyanobacteria, proteobacteria and green sulfur bacteria. The function of gas vesicle is to provide buoyancy for aquatic prokaryotes and to receive sufficient amount of oxygen, light and nutrients.
- Endospores
- resting structure formed by some bacteria for survival during adverse environemental conditions
- germination results in leaving the dormant stage and once again becoming a typical, multiplying cell (vegetative cell)
- high resistant differentiated bacterial cell
- enable the organism to endure extreme environmental conditions
- The structure of spore is more complex than vegetative cell:
- The presence of dipicolinic acid which located in core wall give the resistance properties of endospore because intercalate in DNA and stabilizing it to prevent heat denaturation.
- Genus Bacillus and Clostridium are two common disease causing bacteria that produce endospores as needed.
My own explorace：
1) In group translocation, the substance is chemically altered during transport, preventing it from escaping the cell after it is transported inside. This process requires high-energy phosphate compounds like phosphoenolpyruvic acid (PEP) to phosphorylate the ransported molecule, preventing its movement out of the cell.
2) The magnetotactic bacteria can be subdivided into two categories, according to whether they produce particles of magnetite or of greigite, although some species are capable of producing both. Magnetite possesses a magnetic moment three times that of greigite.
3) The formation of endospores may help maintain the symbiotic association between these Epulopiscium-like symbionts and their surgeonfish hosts. Since endospore formation coincides with periods in which the host surgeonfish is not actively feeding, the cells do not need to compete for the limited nutrients present in the gut at night. The protective properties of the endospores also allow them to survive passage to new surgeonfish hosts. The fish may also benefit from this relationship because it is able to maintain stable microbial populations that assist in digestion and may receive a nutritional gain from microbial products released during mother cell death and spore germination.
Reflection:
I would like to know the benefit of endospore to the environment. People always think that endospore maximize the chance of spreading disease. Actually endospore is not just spreading disease, but it help to maintain the symbiotic association between Epulopiscium-like symbionts and their surgeonfish hosts. Besides that, Bacillus subtilis spores are useful for the expression of recombinant proteins and in particular for the surface display of peptides and proteins. Therefore, everything have their good side and bad side include endospore, bacteria or even virus.
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