14 - Intro to Bacteriology Flashcards
Bacteria prokaryotes or eukaryotes
Prokaryotes
Aechaea prokaryotes or eukaryotes
Prokaryotes
Eukarya prokaryotes or eukaryotes
Eukaryotes
Universal phylogenetic tree
shows evolutionary relationships based on 16S rRNA sequence comparisons
Bacteria
- single-celled
- Cell walls contain peptidoglycan
- no membrane-bound nucleus
- no membrane-bound organelles
Smallest bacterium
Mycoplasma (0.3 μm diameter)
Most common shapes of bacteria
Coccus (cocci) and rods (bacillus/bacilli)
Function of capsules and smile layers
Resistance to phagocytosis, adherence to surfaces
Fimbriae and pili function
Adherence to surfaces, DNA transfer, twitching and gliding motility
Flagella function
Swimming and swimming motility
Endospore function
Survival under harsh conditions
What colour do gram positive bacteria stain
Purple
What colour do gram negative bacteria stain
Pink or red
Gram positive cell envelope
- Cell wall is thick, multi layered peptidoglycan containing teichoic acids
- Plasma membrane
Gram negative cell envelope
- Cell wall is a thin peptidoglycan layer
- Large periplasmic space between outer and inner membranes
- Outer membrane containing lipopolysaccharides (LPS)
- Plasma membrane
Why does gram positive stain purple
Thick cell wall traps crystal violet
Why does gram negative stain pink
Cell wall cant hold crystal violet and is washed away by alcohol and counter stained with safranin
Flagella
- Mediate swimming bacterial motility (flagella rotate to propel the bacteria forward)
- helical proteinaceous structures extending from the plasma membrane and
cell wall
Polar flagella
Flagella at one or both ends of a cell
Peritrichous flagella
Flagella spread over the whole surface of the cell
Pili / Fimbriae
- proteinaceous structures extending from the plasma membrane and cell wall
- Thinner, shorter, straighter than flagella
- Mediate attachment of bacteria to surfaces including host cells
Sex pili
Mediate the transfer of DNA from cell to cell
Type IV pili
mediate twitching motility by extending and retracting to
pull the cell forward