Introduction to Bacteria Flashcards
What do you need to use to see the entire structure of a bacteria cell?
Electron microscope.
Discuss the structure of a bacteria cell.
Single cell, no nucleus.
Contains a cell wall, capsule and flagellum.
Cytoplasmic/inner/plasma membrane,.
Fimbriae
What are fimbriae?
Long filamentous polymeric protein structures located at the surface of bacterial cells
What is a flagellum?
Flagellum is primarily a motility organelle that enables movement and chemotaxis.
Bacteria can have one or several.
Describe the cell membrane of a bacteria cell.
very thin, elastic and semi-permeable membrane
Describe the structure of the cell wall of a bacteria cell.
Cell wall is rigid, giving the cell strength and shape but it is permeable.
How can we differentiate between gram positive/negative cell walls?
Thicker layers of peptidoglycan indicates it is a gram positive cell wall.
Thinner layers of peptidoglycan indicates it is a gram negative cell wall.
Some bacteria, like mycobacterium, cannot be reliably stained. Why?
They have a high lipid content.
In light microscopy. when staining cells, what colour does-
1. Gram positive become
2. Gram negative become
- Purple (think P=P)
- Red
What shape are cocci bacterium?
Small and round
What shape are bacilli bacterium?
Rod shaped.
What shape are spiral/corkscrew bacterium?
Haha lol spinal or corkscrew imagine that
Describe the cytoplasmic membrane.
Made up of phospholipids (40%) and proteins (60%)
Forms a barrier but allows uncharged molecules and water to pass.
5-10nm thick
Name the functions of the proteins in the cytoplasmic membrane.
-Transport systems for specific nutrients and ions.
-Enzymes to be involved in DNA replication, energy generation and cell wall synthesis.
-Sensing proteins which monitor conc. of molecules in the environment.
Describe the cell wall of bacteria cells.
-10-25 nm thick
-Made of peptidoglycan
-Thick, strong and relatively rigid so maintains shape
Which antibiotics can interfere w the construction of cell wall peptidoglycan?
Penicillin
Where are penicillin binding proteins located?
Cell wall cytoplasmic membrane
What is the action of penicillin?
Bind to the penicillin proteins and inhibit the bacterial cell wall synthesis.
What happens if the bacterial cell wall is weakened?
Lysis- cell will swell and burst due to osmosis.
How does the cell wall play a role in cell division?
Cross-walls form prior to separating into 2 daughter cells.
Describe the LPS outer membrane.
-Only present in Gram negative bacteria
-Made up of LPS (lipopolysaccarides)
-Protects peptidoglycan from bile salts (in the gut), also from lysozyme
-Blocks many antibiotics getting into the cell
-Lipid A (within LPS) forms endotoxin, which, when released into the bloodstream (when multiplying or when lysed), may give rise to endotoxic shock.
List to clinical symptoms categorised from endotoxic shock.
Fever and low blood pressure.
Describe the capsule of bacteria cells.
-Polysaccharide layer outside the cell wall.
-Can be rigid or slimy(due to biofilm forming).
What do rigid capsules do?
Prevent phagocytosis.
What do slimy capsules do?
Produce a biofilm and adheres to cells.
Produces microcolonies which protect the cell.
Describe the structure of flagella.
Long thin filament twisted into a spiral.
Often several times the length of the bacteria cells.
Cam be between 1-20.
What do flagella do?
Provide the bacteria cell motility (regarding muscle contraction).
Define Monotrichous in regards to number of flagella.
1 flagella.
Define Lophotrichous in regards to flagella.
More than one flagella comes from one point.
Define Amphitrichous in regards to flagella.
Multiple flagella from multiple points.
Define -Peritrichous in regards to flagella.
All over.
What are fimbriae?
Filaments.
Numerous compared to flagella.
Shorter and thinner than flagella.
Important role in adhesion between bacteria and host cells.
How do bacteria cells replicate?
Using binary fission to produce two identical daughter cells.
How can there be variation in bacterial cell replication?
-Spontaneous mutation.
-Transfer of DNA.
Which enxymes cuts a section of the plasmid and where?
-Endonuclease at the origin of transfer.
What is a bacteriophage?
A type of virus that infects bacteria.
Describe ribosomes found in bacteria cells.
-Consist of RNA and associated proteins
-Function is to synthesise proteins
Describe the number of ribosomes and related subunits.
Bacteria have a 70S ribosomes, with large (50S) and small (30S) subunits
The small 30S subunit has itself a subunit, called 16S.
What happens in the highly resistant resting phase?
Occurs as a endospore
Organism can survive in a dormant state during a period of starvation..
Describe the process of sporification.
- Bacteria cells divides by binary fission.
- DNA lines up along middle of the cell.
- DNA of mother cell divides into two complete copies.
4.Mother cell membrane engulfs developing spore.
5.Developing pore is now surrounded by two membrane layers. - Calcium enters the cortex from the outside of the cell.
- As calcium enters, water is removed from the spore.
- Protein coat forms exterior to the cortex.
- Spore becomes mature.
- Some spores form an additional layer known as the exosporium.
- Lytic enzymes destroy the mother cell and the mature spore is released.
How are individual bacteria’s detected?
Sample is taken from patient and looked at under a microscope.
Stains are often used.
