Bacteriology-Prokaryotic Cell Flashcards
What range can bacteria sizes be?
1micrometer=0.001 mm to 1mm maximum
What do you call spherical shaped bacteria? give 3 examples
Cocci: coccus,
- diplococcus
- chain of cocci
- cluster of cocci
Bacillus describes what type of shape in bacteria?
Rod shape, also includes:
- Diplobacillus
- streptobacillus(chain)
Name 3 types of shapes found in bacteria except for Bacillus and Cocci
1,Intermediary shape (coccibacillus)
- Spiral shape
- Filamentous Bacteria
What are the main differences between Prokaryotic and Eukaryotic cell?
- Prokaryotes are smaller(1-2 micrometers)
- No internal compartments
- Naked circular DNA + Plasmids
- diferent genome sizes(less)
What is the fluid mosaic model
-The plasma membrane is composed of a phospholipid bilayer, membrane proteins, glycolipids, small amounts of carbohydrates arranged in a mosiac pattern causing the membrane to move fluidly
What is the 5 main functions of the Plasma membrane?
- Protection of intracellular space
- Selective permeability
- Site for energy production
- site for synthesis of membrane lipids and cell wall constituents
- Distribution of the genetic material in each daughter cell
What is the bacteria cell wall composed of? How does this relate to gram +/- bacteria?
Cell wall =peptidoglycan (Carbohydrate + Peptide)
G.P= Peptidoglycan has pentaglycine cross links
G.N= Peptidoglycan have direct cross links
What is the main difference between gram positive/negative bacteria?
G.P= LESS COMPLEX, stains deep blue/violet G.N= MORE COMPLEX. extra layer of lipopolysaccharides and larger periplasmic space, results in no colour for gram staining and pink for safranin
Name 3 functions of Bacterial Cell Wall
- maintains rigidity + shape
- protects cell from osmotic lysis
- Contributes to the pathogenicity of certain bacterial species
where is the presence of peptidoglycans in the cell wall absent of bacteria?
Archaea, Mollicutes
give examples of metabolic reserves in the bacterial cell
- Carboxysomes : carbon polymers. Energy and carbon source.
- Poly-β hydroxybutyrate granules : energy and carbon source
- Polyphosphates granules : source of phosphates for nucleic acid
synthesis (or phospholipids, or energy) - Glycogen : energy and carbon source
- Sulfur globules : Energy source. chimio-lithotrophic bacteria
Bacterial chromosome:
Usually single, circular molecule of double-stranded DNA
- From 160kb to 12.000 kb. (E.coli : 4600kb)
- Self-replicating (replicon)
- Essential for survival
Vertical transfer:
parent to daughter cells
Horizontal gene transfer
- Transduction
- Conjugation
- Transformation
Transposons
One type of mobile genetic elements : transposable elements or
transposons (« jumping genes »)
Can carry genes encoding antibiotic resistance
Genetic instability and mutagenesis
Used in genetic engineering
Capsules
Viscous material (polysaccharides, sometimes proteins) that covers the outer layers of the cell, but also to the pili and fimbriae
What are the functions of of the capsules?
resistance to host defenses (phagocytosis, complement mediated lysis)
- prevents desiccation
- some vaccines are based on capsular polysaccharides (anti-capsular antibodies)
(S.pneumoniae, N.meningitidis, H.influenzae)
Common pili (fimbriae)
Involved in biofilm formation (attachment to surfaces)
- Attachement to host cells (virulence factor)
- Prevent phagocytosis (virulence factor)
Flagella
Long, thin helical filament fixed to the cell at one end - Made of flagellin (protein) - Gram + and Gram – bacteria - Motility (chemotaxis : nutrients, other chemoattractants)
What is an endospore?
Some bacteria, when facing unfavorable environmental conditions,
sporulate.
- Can resist to extreme environmental conditions (heat, desiccation,
lack of nutrient,…) for a long time
- No metabolic activity
- Consists of several characteristic envelopes:
