Week 3 Flashcards
Where does the word prokaryote come from?
The greek for prenucleus
Where does the word eukaryote come from?
The greek for true nucleus
What are prokaryote microorganisms?
Archaea and Bacteria
What are eukaryote microorganisms?
Algae, fungi and protozoa
What is the three domain system?
That there are three domains of life which are bacteria, archaea and eukaryotes which all decend from a common universal ancestor
This was proposed by Carl Woese
How can the three domains be distinguished?
By their cell wall
What is an overview of bacteria and their cell walls?
Bacteria are prokaryotic cells. The cell walls of Bacteria, contain peptidoglycan
What are an overview of archaea and their cell wall?
Archaea are prokaryotic cells. The cell walls of Archaea contain pseudo-peptidoglycan. Archaea often live in extreme environment, include extreme halophiles or thermophiles
What is an overview of eukarya and their cell wall?
Eukarya have eukaryotic cells. Not all Eukarya possess cell walls. Cell walls from Eukarya that posess cell wall do not contain peptidoglycan
What is a key difference between prokaryotes and eukaryotes?
Prokaryotes: absence of internal compartmentalisation by membranes
Eukaryotes: presence of membrane bound organelles such as the nucleus, mitochondria and chloroplasts
What is a key feature of prokaryote cells?
High surface/volume ratio
What is an advantage of having a high surface/volume ratio?
bacteria can sense and respond quickly to their environment (despite lack of organelles)
Increased secretion and uptake
What is an example of the difference in surface area/volume ratio in prokaryotes to eukaryotes?
Staphylococcus aureus: 1 um diameter sphere
pid3/6=0.52 um3 volume
pid2=3.14 um2 surface
S/V ratio: 6
Human erythrocyte, 10 m diameter sphere
pid3/6=520 um3 volume
pid2=314 um2 surface
S/V ratio: 0.6
What is the size of most bacteria?
Comparison of sizes of a variety of prokaryotes. Most known prokaryotes have cell diameters in the range of 0.5–2 µm
What is an example of a small bacteria?
haemophilus influenzae
0.25 x 1.25 um
What is an example of a large bacteria?
Oscillatoria (cyanobacteria)
8 x 50 um
What is an overview of the largest bacteria ever discovered?
Epulopiscium fishelsoni
Found in the intestinal tracts of surgeon fish
~ 2000 um long, 1000x longer than the average bacteria
What does a typical bacterium typically consist of?
cytoplasmic membrane within a peptidoglycan cell wall
Fluid cytoplasm contains the chromosome (nucleoid) and numerous ribosomes
What is an overview of the nucleoid?
The DNA is not surrounded by a nuclear membrane (no nucleus)
Single circular chromosome (few exceptions)
How large is E.coli DNA compared to an E.coli cell?
E.coli DNA length ~1400um E.coli length ~3 um
How is DNA packages in bacteria?
histone like proteins (HNS, HU)
Dps proteins
SASP-s in spores
How many ribosomes are their in a bacteria cell?
~15000 per cell
What is the difference between eukaryotes and prokaryotes molecular biology?
Eukaryotes: transcription in nucleus, translation takes place in the cytoplasm
Prokaryotes: transcription and translation take place in the cytoplasm: ribosomes start translation on RNA as it is being transcribed
What is the cytoplasmic membrane made out of?
Structure of a phospholipid bilayer. The cytoplasmic membrane is about 8 nm wide
What is the function of the cytoplasmic membrane?
Permeability Barrier
Generation of proton motive force
How does the cytoplasmic membrane act as a permeability barrier?
Only small, uncharged, hydrophobic molecules can pass through by diffusion
Protein Anchor
Transport, generation of energy, chemotaxis
What is different about Archaean cell membrane and bacteria membrane
Ether link - Archaea Ester link in bacteria
Branched hydrocarban -Archaea unbranched in bacteria
What are examples of storage molecules in bacteria?
C: poly-hydroxybutyrate, glycogen
P: polyphosphate granules
What bacteria produces poly-hydrobutyrate?
Ralstonia eutropha
What is the rough structure of poly-hydrobutyrate?
Poly-b-hydroxybutyrate (PHB). (a) Chemical structure of PHB, a common poly-b-hydroxyalkanoate. Other alkanoate polymers are made by substituting longer-chain hydrocarbons for the –CH3 group on the b carbon
What is a key trait about poly-hydrobutyrate?
Biopolymer with similar properties than synthetic polymers
What is a problem with synthetic polymers?
Synthetic polymers are often generated from Hydrocarbons (non-renewable energy source) non-biodegradable
Why can ploy-hydrobutyrate be used insted of biopolymers?
Renewable
BIODEGRADABLE (generating water and CO2)
What is an overview of gas vesicles?
Made of proteins
Gas permeable, but not water permeable allowing for control of floating properties
Occur in five phyla of the Bacteria and two groups of the Archaea
What are ges vesicles made from?
GvpA associates with GvpC, to build up gas vesicles, hollow protein structures. GvpA makes up most of the structure, as so called “ribs”, rigid β-sheets, whereas GvpC stabilizes the vesicle against collapse by crosslinking as α-helices
What is the function of magnetosomes?
They help orient bacteria
What is key in determining the function and structure of magnetosomes?
MamK (actin homologue) controls the organisation of magnetite particles in magnetosomes
What is the function of magneto-taxis?
Magneto-taxis in the northern (NH) and southern (SH) hemispheres aids cells in efficiently finding their optimum oxygen concentration ([O2]) at the microaerobic oxic–anoxic transition zone (OATZ) in water columns.
What is the difference between magento-taxis in the different hemispheres?
Polar magneto-tactic cells in the NH and SH to have opposite magnetic polarity due to the earths magnetic field working in the opposite direction
How do bacteria in the northern hemispheres travel up?
In both hemispheres, cells on the oxic side (northern hemisphere) of the OATZ swim down along the geomagnetic field lines by rotating their flagella counterclockwise (CCW)/ They rotate the flagella clockwise swim up the geomagnetic field lines
How do bacteria in the southern hemispheres travel up?
Those on the anoxic side (southern hemisphere) swim up along Bgeo by rotating their flagella clockwise (CW). The swim down by rotating flagella counterclockwise
What are the two phases of gram positive bacteria?
sporulation -formation of endospores
germination- return to vegetative growth
What are key features of endospores?
No metabolism
Extremely resistant to extreme environment (heat, desiccation, radiation, acids, chemical disinfectants)
Thick coat, DNA, few ribosomes, few enzymes
May lay dormant for thousands of years, then germinate in the presence of water and nutrients
Made in adverse conditions like the lack of nutrients.
What are the two main phases of vegetative cycle?
Growth - new daughter cells grow
Medial division - binary fission to produce daughter cells
What are the maun stages of endospore formation?
Polar division
Asymmetric cell division
Engulfment
Cortex
Spore coat
Maturation, cell lysis
Germination (when conditions return to habitable)
What are examples of bacteria that can form endospores?
Bacillus, Clostridium (Bacillus anthracis, Clostridium botulinum, Clostridium difficile)
How much water is in dormant cells?
Dormant cell: 15% water vs 70% in normal cells
What is the function of the flagellum?
Responsible for bacterial movement
Rotation of the flagella results in a propeller motion that moves the bacterial cells forward
What are the different types of flagellum?
Monotrichous - single flagellum at pole
Amphitrichous - a single flagellum on each opposite end
Lophotrichous - multiple flagella located at the same point
Peritrichous - multiple flagella around the body
How do Petrichous bacteria move around?
If spin counterclockwise the flagella bundle together and move the bacteria forward
If spin clockwise the flagella are pushed apart creating a spinning movement
How do mono or Lophotrichous bacteria move?
Counterclockwise rotation bacteria move forward
Clockwise rotation bacteria move backwards
What are an overview of Pili?
more numerous than flagella (10-250 per cell)
shorter than flagella ~1 micrometer
function: attachment or sex (occasionally motility)
What is an overview of Axial filaments?
Also called Endoflagella
Periplasmic – between cell wall and outer sheath
in spirochetes
Anchored at one end of a cell
Rotation causes cell to move – like a corkscrew