Bacterial Intracellular Structures That Give Bacteria/Prokaryotes an Advanatage!
Prokaryotic cell structure
Intracytoplasmic Membrane (ICM)
There are two different types of intracytoplasmic membranes in Prokaryotes listed below.
- Magnetosome membrane
- Nitrifying Bacteria ICM
- Photosynthetic Membranes
- Hydrocarbon-oxidising bacteria ICM
Non Units Membranes
- Membrane surrounding some storage granules
- Gas vesicle Membrane
Are tubular involutions of the cytoplasmic membrane in the shape of tubules or vesicles
*Involution occurs when something turns in upon itself. See image to the right to see structure of mesosome.
Emerge with regions associated with cell division, often found next to the septa.
- Cell division
- May be involved in cell wall formation
- Site of phospholipid synthesis
- Site for attachment of DNA (chromosome) during replication
- Not a site of respiratory enzymes (although may look like a mitochondria internal matrix)
Magnetosomes are found in magnetotactic bacteria. These bacteria are found in sediments of freshwater and marine environments.
Within a bacteria Magnetosomes are intracellular crystal particles of the iron oxide magnetite (magnetic particles) enclosed within membrane vesicles.
The image to the right shows how magnetsomes are arranged in the cell, in a linear fashion. Attached to the linear line of magnetsomes are magnetsomes vesicles, which contain magnetic particles.
Function – Magneto taxis
Involving in bacteria directional movement in response to geomagnetic fields.
Bacterial magnetosome membrane
- A tri-laminate membrane which surrounds each magnetic core.
- Most of the proteins are similar to that of the cytoplasmic membrane, however, are unique to the magnetosome membrane called Mam proteins.
- Mam proteins are not joined with cytoplasmic membrane.
Model of magnetite biomineralisation in Magnetospirillum species
The image to the right! Click to enlarge
- Fe (III) is actively taken up by a bacterial cell.
- Iron is reoxidized
- 1/3 of the Fe (III) ions are reduced and magnetite is produced.
Nitrite – oxidising bacteria
- The proteins associated with nitrite-oxidising activity are accociated with particles arranged in rows on the intracellular membrane.
Ammonia – oxidising bacteria
Photosynthetic pigments are integrated into Internal Membrane Systems that arise from:
- Invagination of cytoplasmic membrane. Example Purple Bacteria
- Cytoplasmic Membrane itself. Example Heliobacteria
- Cytoplasmic Membrane and non-unit membrane enclosed structures chlorosomes. Example Green bacteria
- Thylakoid membranes. Example Cyanobacteria
Inclusion Bodies may be organic or inorganic material within the cytoplasm.
- Inclusion bodes not bound to a membrane for example, polyphosphate granules and glycogen.
- Inclusion bodies enclosed by a single-layer, non-unit membrane e.g. Poly-hydroxybutyrate, some glycogen, sulphur granules and gas vacuoles.
These inclusion body membranes vary in composition, some are protein in nature and others contain lipids.
Inclusion bodies include
- Sulphur granules with elemental sulphur
- Carbon storage material
- Poly hydroxybutyrate and Glycogen
- Cyanophycian – nitrogen source
- Carboxysomes - Contain rubulose
- 1,5 bisphosphate carboxylase
- A site of CO2 fixation
- Polyphosphate granules – storage of phosphate
- DNA synthesis or energy reserve
- Gas Vacuole
Sulphur Granules with Elemental sulphur
Bacteria capable of oxidizing reduced sulphur comounds such as hydrogen sulphide and thiosulphate.
- Biosynthesis and energy reactions
When the reduced sulphur is limted, the sulphur granules slowly disappear due to oxidation of elemental sulphur
Example: Achromatium spp (image to the right) showing the granules within the bacterium.
Gas vesicle membrane Structure
- Non-unit membrane
- Proteins are Gvp
- Freely permeable to gases, the partial pressure of gases in the vesicle in equilibrium with the proportion of gases dissolved in the environment
Model of the two proteins GvpA and GvpC that make up the gas vesicle (right)
- Cell buoyancy in aquatic photosynthetic prokaryotes. E.g. plankton, cyanobacteria exhibit these structures
- Enable flotation at suitable high water column for photosynthesis
There you go, some features of the bacterial intracellular structures that bacteria use to thrive in harsh conditions where molecules/ions needed to survive may be scarce.
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