Introduction to bacteria Flashcards
What colour do gram positive cells stain
Purple
What colour do gram negative cells stain
red
What 3 shapes do bacteria exist as
Coccus
Bacillus
Spiral
What is a coccus shape bacteria
Spherical
What is a Bacillus shape bacteria
Rod
What size is bacteria
Most bacteria range from 0.2–2.0 µm
How do bacteria replicate
Binary fission, Asexual replication (DNA doubles and cell divides)
Why do gram negative cells loose colour when stained
as lipopolysaccharide dissolves crystal violet stain, so bacterium remain red
What is bacteria conjugation
Bacteria direct exchange of plasmids (genes)
What bacteria have plasmids
resisting bacteria
What layer does gram negative have
lipopolysaccharide
What causes genetic variation
spontaneous mutation
transfer of DNA
Main function of peptidoglycan
Shape and strength
main function of lipopolysaccharide
Strong immune response
When does spore forming occur
when conditions become adverts and nutrient run out
What happens in spore forming
DNA divided into two copies developing spore engulfed Peptidoglycan forms a cortex around developing spore lytic enzymes destroy mother cell Mature spore cell released
In spore forming bacteria change from once cell to another why?
To survive in adverse environmental conditions
After conjugation what are both bacteria called and what is present in both
F+ cells and both contain identical copies of plasmids
What is a bacteriophage
Virus that parasites a bacterium, injecting and reproducing in it
What is the lysogenic cycle
when material is injected with the DNA from the bacteriophage
What are the three ways bacteria exchange DNA
transformation
transduction
Conjugating
What is bacterial transduction
viruses carry bacterial genes from one bacterium to another
What is bacterial transformation
the bacterium takes up of foreign DNA from its surroundings i.e. dead bacterias DNA
What is MacConkeys Agar
Specialised bacterial growth medium selective for gram negative
Why is MacCokeys agar selective and differential
Inhibits growth of Gram positive
and differentiates between which Gram negative bacteria are lactose fermentors
What does MacCokeys agar contain
Bile salts and crystal violet
Lactose and neutral red ph indicator
What colour does agar turn in the presence of gram negative lactose fermentor
pink
What do you find on the cell surface of bacteria
Plasma membrane
penicillin binding site
peptidoglycan
lipopolysaccharides
Function of peptidoglycan (murein)
Strength and shape
counteracts high osmotic pressure
What is frimbraie
thread like projections used for adherence
What is used to identify strains within a species
DNA typing techniques
What do strains of species have
similar characteristics
Naming bacteria follows what principle
Genus is mentioned then the species
whats the genus and whats the species Staphylococcus aureus
Staphylococcus - genus
aureus - species
How does bacteria conjugation occur aka function of plasmids
transfer resistance from one bacteria to another via the formation of a PILUS; a bridge between two bacterial cells that is used for communication
