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Questions and Answers
How many generations passed if you have 106 cells after 3 hours of exponential growth?
How many generations passed if you have 106 cells after 3 hours of exponential growth?
What is the doubling time if the total time of growth is 3 hours for 10 generations?
What is the doubling time if the total time of growth is 3 hours for 10 generations?
What is the growth rate (k) if the final cell count is 106 and the initial count is 103 over 3 hours?
What is the growth rate (k) if the final cell count is 106 and the initial count is 103 over 3 hours?
Which phase of growth is the most common for cells in natural environments?
Which phase of growth is the most common for cells in natural environments?
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What characterizes biofilms in microbial growth?
What characterizes biofilms in microbial growth?
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What adaptation allows microbes to thrive at high hydrostatic pressures?
What adaptation allows microbes to thrive at high hydrostatic pressures?
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What type of microbial classification would psychrophiles fall into based on optimal temperature?
What type of microbial classification would psychrophiles fall into based on optimal temperature?
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What do halophiles produce to create turgor pressure in high salt concentrations?
What do halophiles produce to create turgor pressure in high salt concentrations?
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Which factor is NOT mentioned as affecting microbial growth?
Which factor is NOT mentioned as affecting microbial growth?
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What is not a characteristic of cells in a biofilm?
What is not a characteristic of cells in a biofilm?
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What is the main significance of the great oxidation event that occurred around 2.4 billion years ago?
What is the main significance of the great oxidation event that occurred around 2.4 billion years ago?
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What distinguishes eukaryotic cells from prokaryotic cells?
What distinguishes eukaryotic cells from prokaryotic cells?
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Which of the following processes describes the mechanism of bacterial cell division?
Which of the following processes describes the mechanism of bacterial cell division?
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What is the role of stromatolites in the study of early life on Earth?
What is the role of stromatolites in the study of early life on Earth?
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Which of the following correctly describes the function of pili in bacteria?
Which of the following correctly describes the function of pili in bacteria?
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What structural feature distinguishes gram-negative bacteria from gram-positive bacteria?
What structural feature distinguishes gram-negative bacteria from gram-positive bacteria?
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During which cell growth phase do bacteria primarily prepare for division?
During which cell growth phase do bacteria primarily prepare for division?
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What is the primary function of gas vesicles in bacteria?
What is the primary function of gas vesicles in bacteria?
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What characteristic is shared by both archaea and bacteria regarding their cell membranes?
What characteristic is shared by both archaea and bacteria regarding their cell membranes?
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Which of the following best defines LUCA?
Which of the following best defines LUCA?
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What type of growth is indicated by the equation $N = N_0 2^n$?
What type of growth is indicated by the equation $N = N_0 2^n$?
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Which cellular structure is responsible for generating energy in bacteria?
Which cellular structure is responsible for generating energy in bacteria?
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What is the composition of the peptidoglycan in bacterial cell walls?
What is the composition of the peptidoglycan in bacterial cell walls?
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Which type of microscopy method is best suited for quantitative cell counting?
Which type of microscopy method is best suited for quantitative cell counting?
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What is the notable difference between endospores and normal bacterial cells?
What is the notable difference between endospores and normal bacterial cells?
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Study Notes
Earth History and Evolution
- Key ingredients for life: essential elements, water, energy
- Oldest rocks: 4.3 billion years ago (bya)
- Significant events in Earth's history
- 4.5 bya: Earth formation (using meteor data)
- 4.3 bya: Oldest rocks in Quebec, evidence for liquid water
- 3.5-3.8 bya: Evidence of microbial life (stromatolites, carbon isotopes, microfossils)
- 2.7 bya: Oxygenic photosynthesis by cyanobacteria
- 2.4 bya: Great Oxidation Event (O2 = 1 ppm)
- 2 bya: Oldest known eukaryotic microfossil
- 1.9-1.4 bya: Multicellular microfossils
- 0.6 bya: O2 at present levels, large multicellular organisms
- Stromatolites: Layered structures formed by sediment trapping, binding, and cementation by microbial films
- Carbon isotopes:
- Organisms prefer "light" carbon (12C) over 13C and 14C, influencing rock composition.
- Microfossils
- Presence of 12C in Greenland rocks (3.85 bya) marks early life
- Origin of life series
- Panspermia: Life originated elsewhere.
- Abiotic formation of components (amino acids and nucleotides)
- Surface catalysis: Using clay minerals as catalysts.
- RNA world: RNA could act as information and catalyst.
- Implications of oxygenated environment:
- Toxic atmosphere conditions.
- New metabolic pathways evolving (presence of SO4²⁻, Fe³⁺, NO₃⁻, oxygen respiration)
- Energetic benefits of oxygen respiration (rapid diversification)
- Creation of ozone layer (O₃) for protection
- Prior to ozone layer, life existed only in water.
- Banded iron formations: Layered sedimentary rocks (deep water deposits) containing iron oxides and silicates.
- Oldest eukaryotic microfossils: Grypania spiralis (alga)
- Eukaryotes: Nuclear membrane, mitochondria, chloroplasts (originating ~2 bya) containing ribosomes (70S, not 80S) with circular DNA, and dividing by binary fission,.
- Having 16S rRNA instead of 18S rRNA suggests early evolutionary relationships.
Bacterial and Archaeal Cell Structure
- Bacterial cell wall: peptidoglycan (murein), containing N-acetylmuramic acid and N-acetylglucosamine, with cross-linking by D-amino acids. This structure is hydrolyzed by lysozyme.
- Gram-positive: Thick cell wall, containing teichoic acids.
- Gram-negative: Thin cell wall, outer membrane (LPS), and periplasmic space.
- Archaeal cell wall: lacks peptidoglycan, has unique lipids (isoprenoids) and ether linkages to glycerol. The cell wall contains pseudopeptidoglycan, B1.3 linkages, and L-amino acids.
- Cell membrane: acts as a barrier between the cytoplasm and external environment (hydrophobic). The phospholipids form a bilayer. Bacteria use fatty acids attached to glycerol via ester bonds, while Archaea use isoprenoids attached via ether bonds. Both maintain fluid structure by using various components that influence fluidity.
- Cell wall: providing structural integrity against osmotic pressure, external environment, and toxins, while allowing nutrients in and waste out.
- Cell membrane uses: Forms osmotic barrier, allowing for energy generation via H+/Na+ gradient. Also used for transport and signaling functions
- S layer: crystalline/ordered structure as outermost layer.
Other Cell Structures
- Capsule/slime layer: Protection from toxins, predators, allows in nutrients, and reproduction.
- Flagella: common form of bacterial movement, often helical shape, rotation driven by PMF, and comprised of flagellin protein.
- Pili/fimbriae: protein filaments used for adhesion and transporting material.
- Spores: allow for survival in harsh conditions, produced when growth is restricted (endospores).
- Cytoplasmic membrane: is the inner membrane that maintains fluidity throughout.
Cell Division and Growth
- Bacterial growth is rapid and often exponential under specific conditions.
- Exponential phase: growth rate is constant, cell number is increasing, and all components increase at the same ratio. Constant doubling time.
- Lag phase: When cells first grow, they adjust their conditions to their new environment
- Stationary phase: nutrients are depleted, and waste products accumulate, so there is no change in cell numbers.
- Death phase: cells die due to depletion of a resource, or waste build-up, etc.
Factors Affecting Growth
- Nutrients: essential elements, water, energy, carbon, nitrogen, and sulfur.
- Temperature: different organisms have optimal growth temperatures.
- Hydrostatic pressure: Organisms that thrive under very high pressure (barophiles)
- Osmotic pressure: the concentration of dissolved solutes in a solution
- pH: Optimal growth for various organisms occurs at a specific pH
- Other factors: light, oxygen, heavy metals, etc
Other factors to consider
-
Internal structures
- Carboxysomes
- Enterosomes
- Gas vesicles
- Magnetosomes
- Poly-beta-hydroxybutyrate (PHB)
- Thylakoids
-
External structures
- Exosporium
- Capsules/slime layer
- Flagella
- Pili/fimbriae
-
Other important concepts to note:
- Nucleoid: Contains DNA- the genome, circular, and condensed.. It may also have linear chromosomes, if the structure requires it.
- Cytoplasm: contains high concentration of ribosomes that participate in protein synthesis.
-
Other concepts:
- Binary fission.
- Microbes adapt to external conditions by forming biofilms for protection against chemicals, antibiotics, and ROS.
- Biofilm formation occurs sequentially: initial attachment, irreversible attachment, maturation of the biofilm structure, and dispersion, allowing separation of individual clusters of cells from each other.
- Types of microbes
- Gram-positive
- Gram-negative
- Psychrophiles
- Mesophiles
- Thermophiles
- Hyperthermophiles
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Description
Explore key milestones in Earth's history, from its formation to the emergence of life. This quiz covers essential elements for life, significant geological events, and the evidence for microbial life dating back billions of years. Test your knowledge on stromatolites, carbon isotopes, and the origin of life.
