Bacterial Cell Structures Flashcards
Prokaryotic vs Eukaryotic:
Cell division
- P= direct cell division by binary fission
- E= mitotic cell division (more complex)
Prokaryotic vs Eukaryotic: Ribosomes
- P= 70S ribosomes
- E= 80S ribosomes
Prokaryotic vs Eukaryotic: Chromosomes
- P= single chromsome w/o a nuclear membrane
- E= many linear chromosomes enclosed in nuclear membrane
What are spherical bact called
Coccus
What are rod shaped bact called
Bacillus
What are the rod like, curved bact called
Spirillum
What are the v long & thin bact called
Filamentous
Whats a “curvier” spirillum bact called
Spirochete
Outer structures of typical bacterial cell (6)
- Capsule
- Cell wall
- LPS
- Flagella
- Pilli
- Fimbriae
Inner structures of typical bacterial cell (6)
- Nucleoid
- Ribosomes
- Endospore
- Storage granules
- Magnetosomes
- Crystalline inclusions
What is it referred to if the glycocalyx is attched to cell & forms rigid layers
Capsule
What is it referred to if the glycocalyx is not attched to cell & is easily deformed
Slime layer
What is the capsule
Polysaccharide material lying o/s the cell
Do gram pos bact have thick/thin peptidoglycan
THICK!!!!
Do gram neg bact have thick/thin peptidoglycan layer
thin!
What is the lipopolysaccharide of gram neg bact composed of
- Lipid A (toxin)
- Core oligosaccharide
- O Antigen
What are flagella
Long thin structures made of protein subunits called flagellin
What is it called when a bact has one flagellum on one side
Polar monotrichous
What is it called when a bact has many flagellum on one side
Polar lophotrichous
What is it called when a bact has flagellum all over it
Peritrichous
What do Spirochetes have to enable corkscrew motility
Axial filaments which are encased within outer membrane
What are fimbriae and what are they made of
- Bristle like fibres on cell surface
- Made of protein
FUnction of fimbriae
To adhere to surfaces
Are pili or fimbriae longer
Pili are longer
Functions of pili
- Attachment to tissues
- Motility
- DNA transfer in some bacteria
How does twitching motility work
- Extension of pili
- Attachment to a surface
- Retraction
- Uses a motor for extension/retraction
How are pili used for DNA transfer
- Pilus makes contact w recipient cell
- Pulls cells together
- DNA transfer occuurs
What is the bacterial chromosome like
Singular, circular, double stranded DNA molecule
How is all the DNA packed into the nucleoid
By supercoiling
What is supercoiling done by
Enzymes called gyrases & topoisomerases
What are plasmids
Circular, double stranded pieces of DNA which replicate seperately from chromosomal DNA
Is the DNA in the plasmid essential for bacrterial survival
No, but its advantageous to have
Plasmid functions
- Antibiotic resistance
- DNA transfer between bacteria
- Synthesis of toxins that kill other bact
- Have enzymes for metabolism of unusual molecules - advantage
Ribosome function
Translate mRNA to protein
How can ribosomes be used to identify bact
As they contain variable v regions which vary per organism
Function of storage granules
- Energy storage
- Structural building blocks
- Used when environmental sources are depleted
what are magnetosomes
Intracellular inclusions of the iron mineral magnetite
Function of megnetosomes
Enables bact to orient themselves & migrate along geomagnetic field lines
What are gas vesicles
Small gas filled structures made of protein
Function of gas vesicles
Confer bouyancy of cells (bact can position themselves in the water for optimum light harvesting)
What are crystalline inclusions & function
They are a type of storage granule.
Produce toxins.
What are endospores
Inert, resting cells
What is endospore formation triggered by
Environmental stress
* Nutrient starvation
* Extreme temp change
Steps in Endospore Formation
- STAGE 1: Bacteria in unfavourable conditions
- STAGE 2: Asymmetric cell division
- Pre spore forms, septum between pre spore and mother cell
- STAGE 3: Engulfment
- Mother cell engulfs pre spore
- STAGE 4: Cortex
- Cortex forms, surrounded by cell membrane & wall
- STAGE 5: Spore coat
- Coat forms around spore
- STAGE 5 & 6: Maturation of spore & cell lysis
- Cell lyses & free endospore released
- STAGE 7: Germination
- When environment becomes favourable
