topic 6: prokaryotes Flashcards
living organisms are classified into 3 domains:
- Bacteria
- Archaea
- Eukarya
which two domains consist of unicellular prokaryotes?
Domain Bacteria and Domain Archaea
what is Domain Eukarya divided into?
the eukaryotes, divided into 4 Kingdoms:
- protists
- fungi
- plants
- animals
prokaryotic micro-organisms
- bacteria
- archaea
prokaryotic macro-organisms
do not exist
eukaryotic micro-organisms
- fungi
- protists
eukaryotic macro-organisms
- plants
- animals
what are the micro-organisms categories?
- bacteria: unicellular prokaryotic micro-organisms
- archaea: unicellular prokaryotic micro-organisms
- protists: eukaryotic micro-organisms (e.g. protozoa, algae)
- fungi: eukaryotic micro-organisms (e.g. yeasts, mushrooms)
- viruses: non-cellular pathogens
who discovered the antibiotic penicillin, and when was it discovered?
- Alexander Fleming
- 1929
prokaryotes are divided into 2 domains:
bacteria and archaea
what are 2 major categories of Domain Bacteria?
- Eubacteria
- Cyanobacteria
what are Eubacteria?
includes pathogenic bacteria => cause diseases
what are Cyanobacteria?
- non-pathogenic
- have chlorophyll, perform photosynthesis => produce oxygen
- live in lakes, oceans
- role in nitrogen fixation
what does Domain Archaea include?
- Archaea (Archaeabacteria): live in extreme conditions
what are examples of Archaea?
- halophiles: in salty lakes
- methanogens: in the digestive track, anaerobes, produce methane
- thermoacidophiles: in acidous, sulfur-rich hot spring, with optimum temperatures of 70-80˚C and pH 2-3
in taxonomy of living organisms, species are broken down into?
- subspecies
- variety
- strain (in bacteria)
how is a species named?
species name = genus + characteristic property
what is an example of naming a species?
Staphylococcus aureus
- genus: staphylococcus
- property: aureus
what does it mean for prokaryotes to have variable morphology?
a variety of shapes
describe the morphology of prokaryotes
(1) spherical shape (cocci)
(2) rod-shaped (rods)
(3) spiral shape
what is an example of a spherical shaped prokaryote?
Staphylococci, Streptococci
(cocci = spherical)
what is an example of a rod-shaped prokaryote?
bacilli (E. coli)
what is an example of a spiral shaped prokaryote?
- Vibrio cholerae: shape C or S
- Spirilla and Spirochetes
what are the characteristics of a prokaryotic cells, different from a eukaryote?
- smaller in size
- absence of nuclear membrane
- absence of membrane-bound organelles (mitochondria/chloroplasts)
- no organized replicative cell cycle (mitosis)
- replicated by binary fission instead
- their cell wall has different composition from eukaryotic cells
what are the structures in a prokaryotic cell, the essential and non-essential?
essential (present in ALL cells):
- cytoplasm
- cell wall
- plasma membrane
- nucleoid (region with circular DNA)
non-essential (present in some):
- fimbriae
- capsule
- sex pillus
- flagella
what are the functions of prokaryotic cell wall?
- maintains cell shape
- protects the cell
- prevents cell from bursting in hypotonic environment (osmotic pressure)
- role in cell division
compare the different cell wall compositions of eukaryotic, bacterial, and archaea cell walls
eukaryotic cell walls:
- made of cellulose (plant cells)
- made of chitin (fungi)
bacterial cell walls:
- contain peptidoglycan
archaea cell walls:
- contain polysaccharides and proteins
- LACK PEPTIDOGLYCAN
what is peptidoglycan?
a network of polysaccharides and polypeptide
what is gram staining?
- staining technique used to classify bacteria in 2 major categories based on cell wall composition
- uses crystal violet dye used for staining (violet color)
what is gram-positive bacteria?
- their cell walls mainly consist of peptidoglycan
- they absorb crystal violet => have a purple (violet) color
what is gram-negative bacteria?
- their cell walls consist of a SMALL amount of peptidoglycan and a LARGE amount of lipopolysaccharides (LPS)
- do not absorb crystal violet => have a pink color
why are gram-positive bacteria violet in color?
the peptidoglycan in their cell walls traps crystal violet
what are some examples of Gram (+) bacteria?
- staphylococci
- streptococci
- micrococci
what are some examples of Gram (-) bacteria?
- Escherichia coli (E. coli)
- Shigella
- Salmonella
what is an example of an antibiotic that targets the peptidoglycan and damages bacterial cell walls?
penicillin
what are the functional differences between Gram (+) and Gram (-) bacteria?
Gram (+) bacteria:
- resistant to physical stress
- sensitive to lysozyme and penicillin
Gram (-) bacteria:
- resistant to lysozyme and penicillin
what is more likely to be antibiotic resistant (antimicrobials/antibacterials)?
Gram-negative bacteria
what is the capsule?
a polysaccharide or protein layer that covers some prokaryotes
what is the capsule associated with?
increased virulence of wpathogenic bacteria
what is virulence?
the ability of an infectious agent to produce disease (pathogenicity) => a measure of the severity of the disease it causes
what are the functions of a capsule?
- protects bacteria from phagocytosis by leukocytes
- protects bacteria from the digestion upon phagocytosis
- protects bacteria from infection by phages and drying
some prokaryotes have fimbriae, which are?
structures that aid with the attachment of bacteria to each other or to other cells that they infect
what is a special type of fimbriae, what is it used for?
special type of fimbriae (longer than regular fimbriae) that allow prokaryotes to exchange DNA
