Lecture 2/3/4: Bacteria & Archaea Flashcards
Which domain is prokaryote in?
Found in 2 domains of life:
1. Bacteria; e.g. E Coli
2. Archaea
Why is prokaryote in 2 domains of life?
Because the cells of Archaea and Bacteria lack a nucleus (definition of prokaryotes = cells lack a nucleus).
Define Prokaryotes
- organisms whose cells lack a nucleus and other organelles. - small, single-celled organisms that have simple structures.
- carry a small amount of genetic material
What are prokaryotic cells surrounded by?
a plasma membrane (but no internal membrane-bound organelles within their cytoplasm)
what is a plasmid?
small, circular DNA molecules that many prokaryotes carry. Different from chromosomal DNA (can provide genetic advantages in specific environments)
Where is the DNA in prokaryotes contained?
in a central area of the cell called the nucleoid (not surrounded by a nuclear membrane)
What are the 3 shapes of prokaryotes?
- Spherical
- Rod-Shaped
- Spiral
What is an example of a spherical shaped prokaryote?
Cocci (coccus = plural):
can occur singly, in pairs or in chains.
think cookie is shape of sphere
What is an example of a rod-shaped prokaryote?
Bacilli (bacillus = plural):
typically occur independently, can sometimes be found in chains
think banana is shape of rod
What is an example of a spiral shaped prokaryote?
Spirilla, range from comma-like to loose coils.
Spirochetes are corkscrew shaped
think spiral = spirilla
How are cell walls beneficial?
- maintains cell shape
- protects cell
- prevents it from bursting in a hypotonic environment
Do prokaryotic cells have a cell wall?
nearly all of them do, yes
Explain hypertonic
more salt outside of cell than inside, therefore water rushes outside of cell (to balance) = shrinkage
What are the results of a prokaryote losing water (hypertonic)?
water loss = inhibits reproduction
Explain hypotonic
means more salt on the inside of the cell than outside, therefore water rushes into cell (to balance) = swelling or even bursting of the cell
- better than hypertonic but could still be an issue
Explain isotonic
things are equal inside and outside of cell = BALANCED :)
What are the cell walls of plants and fungi made up of?
cellulose or chitin
What do most type of cells contain peptidoglycan (cross link of sugars)?
bacterial cells
What is peptidoglycan?
- tough protective wall that surrounds bacteria
- made up of sugars and proteins linked together
- helps keep their shape and stop from bursting when water tries to get in
- makes up most of the cell wall (especially gram positive bacteria)
- anchors other structures
What are archaeal cell walls made of?
other carbohydrates and proteins
- lacks peptidoglycan
What did Hans Christian Gram come up with?
- developed staining technique to classify bacteria into two groups
1. Gram Positive (purple)
2. Gram Negative (pink)
What colour is gram (+) after stained? What does the bacterium look like?
purple, spaced out and kinda larger
What colour is gram (-) after stained? What does the bacterium look like?
pink, closer together and kinda smaller
Which bacteria group (+ or -) has more peptidoglycan? Why?
Gram Positive (+); they rely mostly on this thick layer for protection which is why they have a lot of it.
What is the outer membrane/layer in the Gram (-) bacteria composed of?
contains lipopolysachharides (LPS)
Which bacteria group (+ or -) has less peptidoglycan? Why?
Gram Negative (-); thinner layer of pepti because they have an extra layer of protection called “outer membrane”
What does the extra layer of LPS on gram (-) bacteria do?
- protects the bacteria against certain antibiotics (e.g penicillins)
- (capsule) triggers an immune response for ‘host’ to fight
- (capsule) makes outer membrane less permeable (less leaky, prevent water loss)
- (capsule) enhances adherence to surroundings
What is the sticky layer of polysaccharide (LPS)/protein that surrounds the cell wall called?
capsule
What is ‘Fimbriae’?
- tiny, hair-like “sticky fingers”
- helps the bacteria stick onto things (substrates) and hold on
- smaller and shorter than flagella
What is ‘Flagella’?
- long, tail-like
- allows cell to move at speeds of 50um/s (which is like 300km/hr for their size)
- longer than fimbriae
- contains a motor-like structure
What is ‘Pili’?
- connects two cells together to share DNA
- helps bacteria gain new traits (e.g. antibiotic resistance)
What percentage of prokaryotes can move around?
half ~ (50%)
What does ‘capable of taxis’ mean?
ability to move around
- toward (+ taxis) or away (- taxis) from something, like food or danger
think ‘taxi’ is a way I can move around in a big city
If a prokaryote is moving toward something, which taxis would this be (+ or -)?
+
Explain endospore (simple)
- a tough/protective “sleeping bag” that bacteria make when things get bad (too hot/cold, no food)
- original cell produces copy of its chromosomes and surrounds itself in sleeping bag
when bacteria senses danger, they create endospore to protect themselves. Can go to ‘sleep’ for years and survive harsh conditions and then wake up/start growing again once things get better.
think endospore = end = end of day = sleep = sleep bag
Why are prokaryotes highly successful?
Because they can reproduce fast
How do prokaryotes reproduce? What conditions are needed?
- reproduce by binary fission (cell division = 1 parent cell into 2 daughter cells)
- can only do this if conditions are good
good = enough space, plenty of nutrients (food), clean space (getting rid of waste)
The first Archaea (1st prokaryotes in Archaea) were found in what type of conditions?
in environments so extreme that few other organisms can survive there
What are the type of organisms that love extreme conditions called?
Extremophiles
think greek ‘philos’ = lovers
Define ‘extreme conditions’
- super hot
- super cold
- very salty
What domain(s) do extremophiles belong to?
All 3, but mostly archaea.
What’s the difference between extremophiles and extreme thermophiles?
- EXTREMOPHILES love ANY extreme condition
- extreme THERMOPHILES specifically love extreme HEAT
What type of genus live in volcanic hot springs at 90°C?
Sulfolobus
What’s ‘Symbiosis’? Give example
- when two different living things live together and help each other out, kinda like teamwork
- ecological relationship
- prokaryotes often form symbiotic relationships with larger organisms
HOST = larger organism
SYMBIONT = smaller organism
e.g. clownfish and a sea anemone; clownfish (symbiont) is protected by anemone, and anemone (host) gets cleaned by the clownfish
What are the types of symbiosis (good and bad)?
- Mutualism: both species benefit
- Commensalism: one species benefits while the other is not harmed/helped
- Parasitism: parasite eats the content of cells/tissue/bodily fluid
What are parasites that cause diseases called?
Pathogens
