Microbial structure Flashcards
What is in a bacteria cell
- Glycocalyx (capsule/slime)
- Cell wall
- Plasma membrane
- Nucleoid
- Ribosome
- Plasmid
What is the structure of the capsule
Tightly organised polysaccharide layer that excludes small particles. Typically adhere firmly to cell wall
What is the glycocalyx composed of
Capsule and slime
What is the function of the capsule
- Protects cell from phagocytosis and desiccation
- Promotes adherence to host tissues
What is the structure of the slime
More easily deformed polysaccharide layer, less tightly organised and doesn’t exclude small particles . Loosely attached to cell surface and can be easily lost
What is the function of the slime
Protects cell from immune response. It can prevent access to antibodies
What are pili composed of
It is composed of oligomeric pilin proteins
What are the pili appendage used for and how does it occur
Bacterial conjugation. It forms a tube to enable transfer of plasmids between bacteria
What is the function of pili
It is highly antigenic and plays role in attachment
What are fimbriae
They are not on all bacteria and may contain lectins
What are lectins
They recognise oligosaccharide units on host cells
What is the function of fimbriae
They facilitate bacterial attachment to host surfaces
What are flagella
They are organs of locomotion, composed of flagellin protein
How are flagella driven
A rotatory engine at anchor point on inner cell membrane
What are the 4 classifications of flagella
- Monotrichous - 1 flagellum
- Amphitrichous - 1 flagellum on each end
- Lophotrichous - Multiple flagella on one end
- Peritrichous - Lots of flagella around
What are spores
They are a metabolically inert form triggered by adverse environmental conditions. They are adapted for long term survival allowing regrowth under suitable conditions
What is gram staining
It differentiates bacterial species into 2 groups: gram positive and gram negative
How does gram staining differentiate
Based on chemical and physical properties of the cell walls
What are the components of the cell wall
- Peptidoglycan
- LTA - gram positive bacteria
- LPS - gram negative bacteria
- Outer membrane proteins
What is peptidoglycan
- Polymers of sugars and amino acids
- Forms mesh-like layer outside plasma membrane
- Sugar component
What is LTA
- Complex of teichoic acid and lipids
- Provides cell rigidity
- Recognised by host immune cells
What is LPS
- Essential for function of outer membrane
- Elicits potent immune and inflammatory host responses
- Produces endotoxins
