Prokaryotes 2 Flashcards
Structures and Diseases
Name and describe the steps of a gram stain
Fixation - attach bacteria to a microscope slide
Add Crystal Violet - stains bacteria dark blue
Add iodine treatment - forms complex with violet
Decolourisation - add acetone/ethanol ( Gram + keeps colour, Gram - loses colour)
Counter stain with Safranin - Gram + stay purple, Gram - go pink
Bacteria can either be…
Gram positive or Gram negative
Gram stains determine which
Name the features of a Gram positive bacterial cell wall
90% of wall is peptidogylcan (traps colour0 Is at least 2 layers Provides protection and support Made of polysaccharide No outer membrane More receptive to antibiotics
Name some features of a Gram negative bacterial cell wall
10% of cell wall is peptidoglycan
Contain outer membrane
Contains lipopolysaccharide (LPS)
LPS is toxic - virulence factor
What is lipopolysaccharide (LPS) made of?
o-antigen
core polysaccharide
lipid A
What happens to LPS if a Gram negative bacteria is destroyed?
LPS may stimulate the immune system resulting in septic shock
LPS is a virulence factor - lipid A is toxic part
What are some examples of clostridial diseases?
Tetanus - begins when spores enter wounds
Botulism - begins when toxin ingested in contaminated food
Gangrene - begins when spores enter deep wound
Clostridium Difficile - begins after antibiotic treatment
What is the flagella used for in bacteria?
Movement
4 types of flagella
Monotrichous
Amphitrichous
Laphotrichous
Petritrichous
What is the fimbrae used for in bacteria?
Bacterial Attachment to other bacteria, eukaryotic cells and inanimate objects
Can be virulence factors
What bacterial structure enables DNA exchange?
Conjugative pili - donor bacteria creates a ‘mating bridge’
Can help spread antibiotic resistance
What are the roles of the bacterial capsule/biofilm?
Outermost layer of bacteria Protects against desiccation/phagocytosis Prevent penetration of antibiotics Promotes adherence Important virulence factor
Are bacterial endospores found almost exclusively in Gram Positive of Gram Negative bacteria?
Gram Positive
What is the role of bacterial endospores?
Triggered by a lack of nutrients
Packages its DNA and ribosomes into protective spores (survive for 100+years)
When conditions are favourable, spores germinate
What are the 4 mechanisms of resistance?
- Altered receptor sites - antibiotic doesn’t fit
- Eflux pump - antibiotics removed from cell via pump
- Beta-lactamases - antibiotics broken down by enzymes
- Decreased permeability of plasma membrane - antibiotic can’t enter cell
