Domain: Bacteria Flashcards
What kind of organisms are Bacteria?
Bacteria are unicellular organisms -> prokaryotic cells!
Name 3 shapes of bacteria
- cocci - sphere
- bacilli - rod
- spiral
What is the function of the cell wall in bacteria?
- gives shape
- physically protects cell
- prevents cell from bursting in hypo-tonic environments
What is found in the cell wall of only bacteria
Peptidoglycan.
How does bacteria move?
Bacteria moves in response to chemical stimuli
positive chemotaxis -> towards stimuli
negative chemotaxis -> away from stimuli
What is the difference between gram-positive bacteria, and gram-negative bacteria?
Gram- Positive:
-thick layer of peptidoglycan around cell wall
-often responds to antibiotics
-typically less deadly
Gram-Negative:
-thin layer of peptidoglycan, plus an outer membrane surrounding this
-typically more deadly than gram-positive bacteria
-often does not respond to antibiotics
How do gram-positive bacteria look in a stain? Why?
purple, because the thick layer of peptidoglycan absorbs the stain.
How do gram-negative bacteria look in a stain? Why?
pink, because the outer membrane and thin layer of peptidoglycan do not hold the stain as well
What kind of capsule sometimes covers prokaryotes? What is it made from/what does it do?
Polysaccharide capsule
- Is made from sugars -> this allows it to:
- adherence
- dehydration protection
- resistance to host defenses
How does internal structure of prokaryotic cell differ from eukaryotic cell?
much simpler
- no complex compartmentalization
- have only single chromosome in a ring
- has ribosomes, but different in form and function
What is a plasmid?
Plasmid is a genetic structure in cell that can replicate independent of chromosomes - > “wayward DNA”
How do bacteria reproduce?
Binary fission -> parent cell splits in two, asexual.
What is an endospore?
Is a dormant structure produced by some bacteria that will remain in hibernation waiting for conditions to become right. Main goal is to survive long periods of time
-metabolically inactive and can remain
viable in harsh conditions for centuries
Why are bacteria so prolific?
- they reproduce via binary fission (asexual)
- they’re small
- have short generation time
Why do bacteria adapt so fast?
Because of short reproduction time.
What are 3 ways that bacteria metabolize in regards to oxygen?
- Obligate aerobes - need oxygen for cellular respiration
- obligate anaerobes - oxygen is poison
- facultative anaerobes - will use oxygen if present, but not necessary.
An important process all life on earth depends on that prokaryotes do
Nitrogen fixation - prokaryotes convert atmospheric nitrogen into forms useful for other organisms.
What does metabolic cooperation look like in prokaryotes, how does this benefit them?
Different species of prokaryotes may cooperate which allows them to access different resources they wouldn’t otherwise be able to.
eg. Anabaena has photosynthetic and nitrogen fixing cells that swap metabolic products
What is Biofilm?
- surface coating colonies
- made up of multiple microorganisms
- form specialized proteins to stick to each other and surfaces which makes them difficult to eradicate.
Compare and contrast bacteria and archaea
similar:
- both made or prokaryotic cells
- no nuclear envelope
- no membrane enclosed organelles
- single circular chromosome
- both are tiny
- both reproduce asexually via binary fission
- both have flagella
different:
- bacteria has peptidoglycan in cell wall, archaea does not
- bacteria is negatively affected by antibiotics, archaea is not
- archaea can live in extreme conditions, bacteria can not
- have different proteins
- some bacteria can form endospores, but archaea does not
what does the outer membrane of gram-negative bacteria contain?
lipopolysaccharides
is the major source of genetic variation in prokaryotes?
mutation
