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MMG Chemotaxis and Organelles


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What is chemotaxis?
-when a chemical interacts with a protein on the cell surface and signals the flagellum to spin one way or another
What is temporal sensing?
-bacteria continually sample the encironment and move through increased runs and less tumbles (attractant) or decreased runs (repellent)
What is taxis?
Why do cells do this?
-moving of a cell
-the sense gradients of chemicals or physical agens such as light and move to or away from them
What is phosphorylation of CheY called?
How about mehtylation of MCP?
What indicates an attractant and what movement results?
-low CheA kinase activity which means the cell has de-phosphorylated CheY
-this is attractant so it needs to run (towards it) so the cell would have de-methylated MCP
What chemotaxis signal transduction occurs in a repellent signal?
-high CheA kinase activity leads to phosphorylated CheY. To tumble, repellants must be bound so we have methylated MCP
During mehtylatation of MCP, which binds attractants?
How about repellants?
-de-methylated MCP (run)
-methylated MCP (tumble)
During Phosphorylation of CheY, which one indicates a clockwise spin (tumble)?
How about CCW (run)?
-phosphorylated CheY (tumble)
-de-phosphorylated CheY (run)
What are fimbriae and pili?
-numerous hair-like structures over the surface of a cell for attaching to other cell surfaces
-composed of protein pilin
What are "F" or "sex pilus"?
-a specialized form of pili
-a single pilus forms a bridge between two cells through which DNA from donor cell can move (conjugation)
What is the glycocalyx made of?
-polysaccharides and glycoproteins secreted by cells to accumulate on surface
What two types of glycocalyx are there?
-capsule (well formed and more rigid)
-slime layer (more loosely aggregated)
What functions does the glycocalyx serve?
-attachment to surfaces
-anti-phagocytic (increases pathogenicity)
-prevents desiccation
-food source
What are some types of inclusions in bacteria?
What are these used for?
-Glycogen (energy, carbon [polymerized glucose])
-Poly-Beta-hydroxybutyrate (energy, carbon [lipids])
-Polyphosphates (inorganic phosphate [nucleic acids])
-Sulfur [amino acids]
-Iron magnetite (magnetotaxis [Fe3O4])
What are inclusions?
-granules used to store nutrients, energy, and structural building blocks
What is an endospore?
-spores formed in Gram+ soil bacteria for the purpose of survival when nutrients are low or conditions become intolerable
What makes endospores so sucessful?
-resistant to heat, desiccation, and harsh chemicals
*can remain dormant for thousands of years
What compound is found in endospores that gives it heat resistance?
-dipicolinic acid (not found in vegetative cell) that complexes with calcium to be effective
How does sporulation occur if its genes are inactive?
-cell enters vegetative growth (can take up to 8 hours)
-vegetative genes are turned off and sporulation genes are turned on
Describe steps 1-4 of sporulation
1)DNA replicated
2)DNA align on x-axis
3)cyto membrane invaginates forming forespore
4)membrane grows and engulfs forespore in 2nd membrane: veg cell DNA disintegrates
Describe steps 5-8 of bacterial sporulation
5)cortex of Ca and dipiclinic acid deposited between membranes
6)spore coat forms around endospore
7)endospore maturation
8)endospore released from original cell
What is the function of microtubules?
-vesicle transport and structural integrity
What is the function of mitochondrion?
-energy production
What is the function of ribosomes?
-protein synthesis
What is the function of nuclear pores?
-protein trafficking
What is the function of the Golgi complex?
-protein trafficking and glycosylation
What is the function of the nucleolus?
-ribosome synthesis
What is the function of peroxisomes?
-H2O2 synthesis
-protein degradation
What is the function of nucleus?
-DNA replication transcription
What is the function of Chlorosplasts?
What is the function of lysosomes?
-portein degradation
What is the function of microfilaments?
-vesicle transport
-structural integrity
What is the function of smooth ER?
-protein trafficking
What is the endosymbiosis theory?
-postulate that membrane-bound organelles in eukaryotes evolved from symbiotic bacteria residing in cytoplasm of primitive eukaryotes
What might have given rise to mitochondrion?
-aerobic bacteria
What may have given rise to chloroplasts?
-phototropic bacteria
What does the smooth ER do?
Rough ER?
-plays role in lipid synthesis
-protein synthesis from ribosomes on its surface. It transports these
How does the Golgi Body process molecules for transport out of cell?
-creates secretory vesicles that fuse with cytoplasmic membrane
Where does respiration occur in eukaryotic cells?
Where does oxidative phosphorylation occur and what is it known as?
-mitochondria (in cristae)
-ATP production
What is a choloroplast in more depth?
-found in algae
-site of photosynthesis
-contains outer membrane and flattened membrane discs (thylakoids) where ATP is produced
What are 5 functions of a eukaryotic cytoskeleton?
1) anchor organelles
2) cytoplasmic streaming and movement of organelles
3) cell contraction
4) movement during endocytosis and amoeboid action
5) provides basic shape
What is the eukaryotic cytoskeleton made up of?
-tubulin microtubules
-actin microfilaments
-intermediate filaments (composed of various proteins)
What is microbial growth?
-an increase in number of microbes rather than size
(such as reproduction)
What is bacterial division?
-equal division into two replicates through binary fission after all cellular constituents are doubled
How can fungus divide?
-filament (hyphae) elongation
What is cell division called?
-cytokinesis (partitioning of cellular constituents into two cells and then separating them)
How does cytokinesis occur?
-bacterial Fts proteins interact to form a divisome
-FtsZ molecules form a ring structure and directs a new cell wall (septum) and subsequent constriction of walls
-cell separation
*this process is actively being pursued as an antibacterial drug target
In eukaryotes, how does cytokineses occur?
-results from contraction of an actin-myosin contractile ring
-in eukaryotic microbes with walls, this is followed with septum formation (algae, fungi)
How can exponential growth be expressed methematically?
-as a geometric progression
g= generation time
n=# of doublings
t-total time of expo growth
Problem: You inoculate a culture of 1 x 103 (N0) bacteria and grow them under exponential growth conditions with a generation time of 30 minutes (g). At what time (t) will the number of bacteria equal 1 x 106 (N) ?
t = g x n = 30 min. x 3.3 ( log N - log N0) = 30 x 3.3 (6 - 3) = 300 min
n is the number of doublings/generations. What is an equation for this if we have N and N nought?
n = 3.3 ( log N - log N0)
What are three ways to measure microbial growth?
1) viable cell count
2) total cell count
3) turbidity
How do you perform a viable cell count?
-use serial dilutions of 10 and plate each one
What are the pros of viable cell count?
How about disadvantages?
-plate count: only live cells can grow
-very sensitive and accurate
+tedious and time consuming
What are the pros and cons of total cell counts? How are they done?
-microscope count
-no pros (besides cheap)
-disadvantages: dead cells can look like live cells, tedious and time consuming
What does a turbidity test measure?
-measure reflected light off cells and finds O.D.
How do you create data using turbidity measurements?
-By taking O.D. reading at time 't' AND doing a plate count you can get actual cell number
ADVAN: quick and easy
DIS: larger cells bias and dead cells scatter light too
What are the 4 stages of a typical growth curve?
1) lag phase
2) exponential phase
3) stationary phase
4) death phase
What is the lag phase?
-adjustment to new environment; length of lag phase depends on growth state of starting culture; increases in ribosomal synthesis, RNA, DNA
What is the exponential (log) phase?
-rapid uniform growth; alsmot all cells are alive optimally using nutrients and producing waste
What is stationary phase?
-number of living cells equal number of dead cells: running out of nutrients and buidling up wastes; no net change in cell number but metabolism continues
What is the death phase?
-cells are dying due to lack of nutrients and waste build-up; decrease in viable cell count but no change in O.D; eventually O.D. will decrease-lysis of cells
What is catabolism?
biological reactions that produce energy and carbon flow used by anabolic reactions
What is anabolism?
all the biosynthetic reaction in the cell; they require energy and carbon flow
What is meant by a cell being an 'open system'?
-nutrients needed for anabolism flow in and waste products from catabolism flow out
What two major things do microbes need for nutrition?
-a carbon source
-an energy souce (ATP)
Why are carbon source needed for nutrition? What type of carbon do heterotrphs use? Autotrophs?
-needed for making macromolecules
-hetero: organic carbon-sugars and proteins
-auto: inorganic carbon-CO2
What energy sources are needed for making ATP?
-light (photoautotrophs)
-chemicals (chemotroph)
-inorganic molecules like NH4, Fe, H2S (lithotroph)
-organic molecules like sugars and proteins (organotroph)
What types of nutrition classes can eukaryotic microbes be?
-saprophytes (fungi protozoa): feed on other organisms
-photoautotrophs (algae): use light and inorganic carbon
What are 6 major macronutrients?
1) Carbon
2) Hydrogen
3) Oxygen
4) Nitrogen
5) Phosphorus
6) Sulfur
What macronutrients make up the backbone of all organic molecules (sugars, lipids, proteins, DNA, RNA)?
-Carbon, Hydrogen, and Oxygen
What is Nitrogen used for in anabolism?
-proteins, DNA, RNA, derived from ammonia(NH3), nitrate (NO3), or N2 gas
What is Phosphorus used for in anabolism?
-DNA, RNA, lipids
What is Sulfur used for in anabolism?
-Amino acids, vitamins
What 5 ions (salts) are important in anabolism?
1) K
2) Mg
3) Na
4) Ca
5) Fe
What are the 5 major ions in anabolism used for?
-cofactors for enzymes, stabalize protein and cell wall structures, regulate osmolarity, etc
What are micronutrients and growth factors needed for in anabolism?
-required in small amounts
-metals or vitamins needed as co-factors for enzymes (chromium, Mn, Ni, etc.)
What are 4 environmental factors affecting bacterial growth?
-osmotic factors
How does temperature affect bacterial growth?
Affects enzyme reactions (metabolism):
-protein-protein interactions
-protein folding
-membrane structures and permeability
What are some ways temperature is used to control bacterial growth?
-refrigeration for mesophiles
-freezing for psychrophiles
-heating/boiling to sterilize
-human fever
In what order would you put the 4 thermophiles from freezing to boiling temperatures
What thermophile is the source of Tag DNA polymerase and what is this used for?
-Thermus aquaticus
-enzyme used in polymerase chain reaction (PCR) experiments
How does pH affect bacterial growth?
-affects protein structure and proton gradient (which is essential for bacterial ATP synthesis)
How do osmotic effects change bacterial growth?
Why is this important to human life (food)?
-if Na content changes more outside cell, water will leave. Too high and cell can't compensate: inhibited growth
*basis of salt and sugar preservation
What halotolerant bacteria will contaminate preserved food and give food poisoning?
-Staphylococcus aureus
How does oxygen affect bacterial growth?
-lethal to some anaerobes
What are 5 classes of oxygen use for bacteria?
1) obligate/strict aerobe
2) obligate/strict anaerobe
3) facultative aerobe
4) microaerophile
5) aerotolerant anaerobes
Describe each of the following:
facultative aerobe
aerotolerant anaerobes
-grow under aerobic or anaerobic conditions
-only use O2 at lower concentrations than air
-tolerate and grow in O2, but can't use it
What broth is used to reduce O2?
What dye is added to show oxidation?
What are four molecules formed by a host defense cell to kill invading microbes?
-Hydrogen peroxide
-Hydroxyl radical
What do superoxides kill?
OH radical?
-destroys lipids and other organics
-damaging but not as toxic
-oxidizes any molecule in cell
Which bacterium (aerobes or anaerobes) have enzymes that can destroy certain toxic intermediates?
What are they?
a) catalase
b) peroxidase
c) superoxide dismutase
d) superoxide dismutase/catalase in combination
e) superoxide reductase
Why can't anaerobes be around oxygen?
-They don't have enzymes to destroy oxygen intermediates, so they build up to toxic levels
Does Staph or Streptococci produce catalase?
-staphylococci does

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