Bacterial Cell Structures Flashcards
How many ribomsomes are there in Prokaryotic cells vs Eukaryotic cells
Pro - 70S Ribosomes
Euk - 80S Ribosomes
Diff bacterial cell morphology and examples
- Cocci - e.g streptpcoccus pneumoniae
- Bacilli - e.g bacillus subtilis
- Spirilla - e.g vibrio cholerae
Other - filamentous, star-shaped, pleomorphic
What is the polysaccharide material that makes up the capsule called?
Glycocalyx
Most capsules are polysaccharide but some are proteins
Capsule VS Slime layer
-If attached to cell and forms a rigid layer - capsule
-If not attached to cell and easily deformed - slime layer
What is the lipopolysaccharides of Gram neg bacteria composed of?
O-Antigen that is recognised by the immune system
Core oligosaccharide
Lipid A - toxin
What protein subunits are the flagella made of?
Flagellin
How do flagella move?
The base region spin- due to hydrogen ions - causes top to spin
Flagellar distribution - peritrichous
Flagella are all around the capsid
Flagellar distribution - Polar monotrichous
Flagellum (SINGLE) come out one end
Flagellar distribution - polar iophotrichous
Many flagella come out one end
What do spirochetes have that are different to other bacteria with regards to motility?
Spirochetes have axial filaments which enable corkscrew motility - allowing penetration of tissues
What are fimbriae, made of and func?
Fimriae are shorter than flagella and more numerous
Made of proteins
Not present in all bacteria
Used to adhee to surfeces like specific tissues
What are pili?
Pili are longer than fimbriae
Fewer present on cell
Involved in attachment to tissues
Involved in motility and DNA transfer in some bacteria
How do pili move the cell?
Type IV pili
Pili extension
Attachment to a surface
Retraction
-uses a motor for extension and retraction
How is pili involved in DNA transfer?
Pilus makes contact with recipient cell, pulls cells together and DNA transfer occurs
Where is the DNA aggregated in bacteria?
In a dense area called the nucleoid - no nuclear membrane
What are bacterial chromosomes structurally?
Singular, circular, double stranded DNA molecule
How is DNA packed into the nucleoid?
-Packed in an organised way to enable transcription- supercoiling
What enzymes do the supercoiling of DNA?
What are these supercoiled domains stabilised by?
Supercoiling is done by enzymes called gyrases and topoisomerases.
These domains are stabilised by structural proteins
What are plasmids and are they necessary for bacterial survival?
Circular double stranded pieces of DNA which replicate separately from chromosomal DNA
-Not essential for bacterial survival
-Capable of being transferred between bacteria
Types of plasmids and their gene fuctions and examples
- Resistance - antibiotic resistence - e-coli
- Fertility - conjugation and DNA transfer between bacteria - e-coli
- Killer - synthesis of toxins that kill other bacteria - e-coli
- Degradative - enzymes for metabolism of unusual molecules - p.putida
Combined prokaryotic ribosome - how much in each subunit?
70S ribosome total
- 30S small subunit composed of 16S rRNA + 21 proteins
-50S large subunit composed of 23S rRNA + 30 proteins
What is the S when giving ribosomes a unit?
Svedberg units = a measure of how quickly particles sediment in an ultracentrifuge
-the larger the particle the greater its S value
-Smaller subunit of ribosome sinks slower than the larger subunit
Why do bacteria have storage granules/inclusion bodies sometimes?
Most of time for energy storage or structural building blocks - use when environmental sources are depleted
-most common is poly-b-hydroxybutyrate (PHB)
-can also contain glycogen, polyphosphate, iron oxide or elemental sulphur
What are magnetosomes and why do bacteria make them?
Magnetosomes are intracellular inclusions of the iron mineral magnetite
-Gives a permanent magnetic dipole to cell
-Enables bacteria to orient themselves and migrate along geomagnetic field lines
What are gas vesicles made from and why do bacteria have them?
Gas vesicles are small gas-filled structures made of protein
They allow buoyancy on cells
Common in cyanobacteria
What is the Bt toxin?
a crytalline protein that is produced by Bacillus thuringiensis - breaks down the cells lining gut in insects
Features of endospores and examples of bacteria that produce endospores?
-Endospore formers are usually found in soil
- Normally triggered by environmental stress
-Very resistent to heat, drying, freezing, radiation, chemicals
-Can survive million sof years
Usually part of Bacillus or Clostridium genera
What is sporulation and germination?
Sporulation = the production of an endospore
Germination = endospores converting back to vegetative cells
What are the 3 categories of bacterial endospore formation
- Terminal
- Subterminal
- Central
