What are the 3 domains of life
Bacteria, Archaea, Eukaryotes
Prokaryotes
- simplest, smallest and most abundant cells on earth
- bacteria and archaea
- lack nucleus and complex organelles
How do bacteria reproduce
binary fission
T/F: fast growing bacteria are more efficient/evolved than slow growing bacteria?
FALSE
What is the generation time for fast and slow growing bacteria?
Fast: ~ 10 mins
Slow: ~ 24 hrs
What are the 3 classifications of bacteria by shape
Coccus, Rod, Spirillum
Obligate aerobe
requires oxygen for growth (e.g humans)
obligate anaerobe
oxygen is toxic for growth
Facultative anaerobe
can use oxygen if present, but can also grow without oxygen
Aerotolerant anaerobe
does not use oxygen but oxygen is not toxic
Microaerophile
grows best with low levels of oxygen
What is a bacterial strain?
strains are genetically different bacteria - it is like a “name”
- NOT ALL “e.coli” are the same, there are different strains
Gram Stain
Stain used to classify bacteria, created by Hans Christian Gram
What are purple bacteria on the gram stain?
Gram Positive
What are pink bacteria on the gram stain
Gram Negative
What is the process of Gram Staining?
- take swab of bacteria and put on a glass slide
- heat the slide
- flood with crystal violet dye
- add iodine solution which fixes the purple stain into the cell wall
- wash cells with alcohol to get wash dye off (for gram positive bacteria, the dye will remain)
- add counterstain to stain everything that the dye washed off from previously
What are two cases you cannot use the gram stain?
- Mycobacteria (use acid fast)
- bacteria that have no cell wall (mycoplasma)
Gram positive cell envelope
- cell wall is outside the cytoplasmic membrane
- cell wall is very thick and this structure is what maintains the purple
- no outer-membrane
- no periplasm
- have teichoic acids in cell wall
Gram Negative Cell Envelope
- has cell wall but it is very thin
- more complex
- have a second membrane (outer membrane)
- between two membranes there is a “periplasm”
- also have lipopolysaccarides
Another name for Bacterial Cell Walls
- also called peptidoglycan
Describe bacterial cell walls
- rigid structure surrounds bacteria (like a fence)
- prevent osmotic lysis
- gylcan backbone made up of two sugars that are linked together via peptides
- synthesis of cell wall is a major target for cell antibiotics
What are the two sugars that make up the glycan backbone? Of the two sugars, which are cross-linked together via peptides
N-Acetylglucosamine (G) and
N-Acetylmuramic acid (M)
Three components that make up Lipopolysaccharide (Endotoxins) and their functions
O-specific polysaccharide (aka O antigen):
- that sticks out of the surface of bacteria
- Immune system can recognize this and develop antibodies against it
- highly variable
Core polysaccharide:
- Links the O antigen and Lipid A
Lipid A:
- this is the part that actually sticks into and is part of the membrane
- Doesn’t vary much
- Good target for innate immune system to go after and recognize bacteria
- recognized by innate immune system and cause hyper-inflammation, producing cytokine storm and then septic shock
Sometimes bacteria will change this part of the lipopolysaccharide so that it is not recognized by the immune system. Which is it?
O antigen
