Prokaryotes Flashcards
LO
Understand major theories on the origin of life
Appreciate the diversity of prokaryotic life
With reference to bacteria
With reference to archaea
Describe the key differences between bacteria and archaea
morphology
Selective forces may be involved in setting the morphology
- Optimization for nutrient uptake
- Swimming motility in viscous environments or near surfaces e.g. spiral-shaped cells
- Gliding motility e.g. filamentous bacteria
importance of cell size scaling
Surface area to volume ratio key for diffusion across membranes and within cytosol
Cell wall
2 points
rigid layer present outside the cytoplasmic membrane
confers structural strength on the cell and protection from osmotic lysis.
cell wall properties
4 points
- Relatively permeable and most microorganisms have one.
- Stronger than the membrane, give shape and rigidity to the cell.
- Prevents lysis due to osmotic pressure.
- Main discriminatory character between different groups of bacteria.
S-layer
3 points
- Crystalline cell-surface layer on some bacteria and most archaea
2. Comprised of glycoproteins Protects the cell from the environment: Bacteriophage Low pH Lytic enzymes Predatory bacteria
- Additional functions:
Surface adhesion
Biomineralisation
Membrane stabilisation
bacteria colonies
bacteria grow on solid media as a distinct colony originating from a single mother cell;
therefore, all cells in a colony are ‘clones’
Descriptive characteristics of a colony:
Form
Elevation
Margin
Colour (substrate/aerial)
see desktop for colony / bacteria morphology
.
Motility
2 points
- Microbial locomotion is a differential characteristic within bacteria.
- Movement allows cells to reach different parts of their environment under their own power.
motility 2 main mechanisms
Flagella
Gliding motility
Flagellum/Flagella
3 points
- The flagellum is a thin, whip-like, motility structure in bacteria.
- Rotor driven by proton-motive force, or sodium gradient
Unloaded speed up to 17,000 rpm, with flagellum up to 1000 rpm. - Direction/speed can be changed in response to environmental conditions.
Gliding
4 points
- Movement across solid surfaces of some bacteria that lack flagella.
- Slower and smoother than flagellar motility
- Movement occurs along the long axis of the cell.
- Types:
polysaccharide production
twitching motility: type IV pili
movement of cell’s proteins
Sporulation
3 points
- A dormant, tough, and temporarily non-reproductive structure produced by certain bacteria in response to adverse changes in the environment
- One spore can survive for thousands of years.
- Major medical issue:
Closdridioides difficile
Bacillus anthracis
Clostridium botulinum
sporulation cycle (see picture on desktop)
.
Spore formation and morphology (see picture on desktop)
.
Reproduction
Asexual reproduction by
3 points
Binary fission
Budding
Fragmentation
Reproduction
Conjugation
2 points
- Most bacteria can conjugate
- Conjugation occurs via pili: there is a donor cell containing a conjugative plasmid and a recipient cell which does not. Only donor cells have pili.
Reproduction
Tranformation
3 points
- Uptake of ’naked’ extracellular DNA
- Induced by environmental stresses
- DNA uptake via competence pili
Reproduction
Transduction
- Transfer of DNA via bacteriophage infection
Metabolism see desktop for diagram
.
Compartmentalisation
(organelle-like structures)
Storage of carbon/ nitrogen/ phosphorus
3 points
- PHB, starch granules
- Polyphosphate
- Nitrate
Compartmentalisation
(organelle-like structures)
Protection of the cell from toxic intermediates of metabolic pathways
3 points
- Encapsulin nanocages
- Ferritins
- Bacterial microcompartments
Compartmentalisation
(organelle-like structures)
Enhancement of speed/efficiency of metabolic pathways
2 points
- Carboxysomes
2. Lumazine synthase
Traditional bacterial classification
‘artificial’ based on arbitrary morphological and biochemical characteristics.
recent molecular and structural work has revealed
as much diversity within Bacteria as within all eukaryotes.
Molecular phylogenetics now reveals
underlying phylogenetic relationships between bacteria.
Archaea the microorganisms of
the extreme environments
but they are present in much more common habitats too
Archaea
Cell Morphology
6 points
- Coccus
- Bacillus
- Filamentous bacteria
- Triangular
- Square
- Irregular shaped
Archaea
size
- most <1um
Archaea
cell wall
3 points
- No peptidoglycan
- Typically no outer membrane
- s-layers, psuedomurein or other polysaccharides
Archaea
cell wall - s layers
- Most common cell wall type among Archaea
- Formed by proteins or glycoproteins
- Paracrystalline structure
Archaea
psuedomurein
- Found in cell walls of certain methanogenic Archaea
- Polysaccharide similar to peptidoglycan
- Composed of
N-acetylglucosamine and
N-acetylalosaminuronic acid
Archaea
Colony morphology
2 points
- no difference in colony morphology between Bacteria and Archaea.
- At first all Archaea were considered Bacteria.
Archaea
Motility
5 points
- The Archaellum: Archaeal flagella
- Thinner than bacterial flagella
- Make a rotation (but their motor is still unknown)
- Different composition (including some glycoproteins)
- Probably slower due to its size
Archaea
Sporulation
No known archaeal species sporulates!
Archaea
reproduction
similar to bacteria
Archaea, rather than being the most primitive bacteria are a
highly diverse group of highly evolved prokaryotes
the sister clade to all Eukaryotes.
Archaea
They are present in
many different habitats (and play key roles in extreme environments.)
Ancestral eukaryote probably arose from
endosymbiosis of a bacterium within an archaeal cell!
Main differences between bacteria and archaea
5 points bacteria
6 points archaea
Bacteria
- Peptidoglycan in cell wall
- Movement by gliding
- No histones
- Only one RNA polymerase
- Inhibited by streptomycin and chloramphenicol antibiotics
Archaea
- Psedopeptidoglycan in cell wall
- Can grow over 100 ºC
- Histones associated with DNA
- Several types of RNA polymerase
- Not inhibited by streptomycin and chloramphenicol antibiotics
- More eukaryotic-like proteins – additional organisation of cytosol
similarities between bacteria and archaea
6 points
- Prokaryotic cells
- Circular chromosomes
- Lack nuclear envelopes
- No membrane-enclosed organelles
- Possess cell wall
- Presence of flagella
the name given to the last universal common ancestor.
LUCA
Classification of microorganism has changed through the time thanks to
newly developed technologies.
Diversity among Bacteria and Archaea is
really high.
Some differences could be observed in morphology, size, structure, motility and resistance forms.
Archaea have been studying as an independent domain for fewer years =
some of their systems are still less understood than in Bacteria.
origin of life
look up miller urey experiment
look up panspermia
bacterial morphology 1
desktop
