Microbial Nutrition

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Microbial Nutrition

• Gary Andersen
• Reference Chapter 2,5,6, 7, 8, 9 Microbiology by
  Tortora, Funke Case

Metabolism
Chemical Substances
Cell
Growth
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What do microbes eat?
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Composition and Nutrition of Cells

• 96 of cells are composed of HCNOPS.
• Macronutrients are nutrients required in larger
  quantities. (carbohydrates, proteins, fats and
  other CHO molecules)
• Micronutrients are nutrients required in trace
  amounts. (Mn, Zn, Cu, Ni)

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Where are the Elements Used?
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Sources of Nutrients

• Carbon CO2 in air and rocks ?organisms
• Nitrogen N2 in air, NO2, NO3, NH4 in soil and
  water ? organisms (NH3)
• Oxygen O2 in air, inorganic salts SO4, PO4,
  NO3, H2O
• Hydrogen Water, Organic compounds in organisms
• Phosphorus Rocks and minerals ? organisms
• Sulfur Rocks and minerals ? organisms

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Microbe Nutritional Types

• Autotrophs Self feeder
• Photoautotrophs Photosynthetic (energy from
  light)
• Chemoautotrophs Energy from simple inorganic
  chemicals
• Methanogens Metabolize H2 and CO2 into CH4 and
  H2O
• Heterotrophs Other feeder
• Chemoheterotroph Obtain carbon and energy from
  organic compounds. CnH2nOn O2 ? CO2 H2O ATP
  (Adenosine tri-phosphate)
• Saprobe Free living organisms that feed on dead
  organisms
• Parasite Derive nutrients from the tissues of
  hosts.

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Microbial Clean-Up The 1989 Exxon Valdez oil
spill left great quantities of pooled oil on
sites in the Gulf of Alaska, such as on Green
Island
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Microbial Clean-Up Bioremediation in 1989, by
the application of nutrients (nitrogen and
phosphorus) to the shoreline accelerated the
bacterial biodegradation of the oil into carbon
dioxide and water
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Microbial Clean-Up In 1991, the area was
surveyed and found to be mostly cleared of oil,
with no further treatment recommended
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How do Microbes Eat?
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Transport Mechanisms

• Passive Transport
• Diffusion Movement of molecules from a high
  concentration to a low concentration.
• Facilitated Diffusion- diffusion assisted by
  conformational change in a protein molecule.
• Osmosis Diffusion of water through a
  semipermeable membrane
• Active Transport Moving particles against the
  diffusion gradient using membrane proteins and
  expending energy.
• Endocytosis Engulfing with cell membrane and
  forming a vacuole.
• Phagocytosis Engulfing of cells or particles by
  the cell membrane
• Pinocytosis Engulfing of liquids by the cell
  membrane

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Passive Transport

• Osmosis animation http//www.tvdsb.on.ca/westmin/
  science/sbi3a1/Cells/Osmosis.htm

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Comparing Solutions

• Hypertonic Solution Higher solute
  concentration. Cells in hypertonic solutions
  lose water and the cell membrane shrinks away
  from the cell wall. (Salt on a slug)
• Hypotonic Solution Lower solute concentration.
  Cells in hypotonic solutions take on water and
  swell. (Prune wrinkles of skin)
• Isotonic Solutions Solutions that have reached
  an equilibrium with a cell or another solution.
  The concentration of solute is equal and the
  diffusion of water proceeds at equal rates.

(See page 93 of text for what happens to a cell
in hypertonic and hypotonic solutions.)
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Animations of Passive and Active Transport

• http//programs.northlandcollege.edu/biology/Biolo
  gy1111/animations/transport1.html
• http//highered.mcgraw-hill.com/olc/dl/120068/bio0
  2.swf

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How do microbes metabolize nutrients?Fermentati
on and Respiration
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Enzymes

• Provide a surface on which reactions take place
• Active site the area on the enzyme surface
  where the enzyme forms a loose association with
  the substrate
• Substrate the substance on which the enzyme
  acts
• Enzyme-substrate complex formed when the
  substrate molecule collides with the active site
  of its enzyme
• Enzymes generally have a high degree of
  specificity
• Endoenzymes (intracellular)/exoenzymes
  (extracellular)

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The Action of Enzymes on Substrates to Yield
Products
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Each substrate binds to an active site, producing
an enzyme-substrate complex. The enzyme helps a
chemical reaction occur, and one or more products
are formed
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Competitive Regulation and Inhibition of Enzymes
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Noncompetitive (allosteric) inhibition of enzymes
http//highered.mcgraw-hill.com/olc/dl/120070/bio1
0.swf
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Factors Influencing Enzymes

• Temperature
• pH
• Concentration of substrate, product, and enzyme

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Relationship between temperature and enzyme
activity
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Microbes and Environmental Factors

• Temperature
• pH
• Oxygen
• Pressure
• Extremophiles Organisms that can survive under
  extreme environmental conditions. An interesting
  source of chemical products.
• Interesting Website on Extremophiles and Chemical
  Products http//www.mediscover.net/Extremophiles.
  cfm

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Temperature

• Classification
• Psychrophile
• Mesophile
• Thermophile

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Temperature

• Thermophiles organisms that grow at gt45 degrees
  C.
• Pyrococcus fumarii is an example of a thermophile
  that can survive at 113 C.

Thermal pool
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Grand Prismatic Spring
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pH
14 Alkaline 13 12 11 10 9 8 7 Neutral 6 5 4 3 2 1
0 Acidic

• Acidophiles grow at low pH levels. (1-2)
• Alkalinophiles live at high pH levels. (9-10)

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Pressure

• Barophiles organisms that grow at elevated
  pressure (3-1000 x air pressure). (Found in ocean
  depths often in thermal vents)

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Presence of Oxygen

• Aerobe Organism able to use O2 in metabolism.
• Anaerobe Organism unable to use O2 in
  metabolism.

Obligate aerobes - oxygen mandatoryObligate
anaerobes - oxygen toxic Facultative anaerobes
Aerobe that can also live without
O2 Microaerophiles - low oxygen levels
required. Aerotolerant - anaerobic metabolism,
oxygen not toxic
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Microbial Processing of Oxygen

• Step 1 O2- O2- 2H ? H2O2 O2
  (Catalyzing enzyme is Superoxide dismutase)
• Step 2 H2O2 H2O2 ? 2H2O O2 (Catalyzing
  enzyme is Catalase)

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Living without Oxygen.Glucose Fermentation
Pathways
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Glucose FermentationNet and practical results

• Cells get chemical energy (ATP)
• Fermentation products are natural waste products
  useful to humans
• Fermented beverages
• Bread
• Cheese
• Yogurt

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Using fermentation metabolism to identify
microbes A positive (yellow) mannitol-fermentati
on test. This test distinguishes the pathogenic
Staphylococcus aureus
(MSA) Test Mannitol Salts Agar
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Comparing Aerobic Respiration with Anaerobic
Fermentation

• Fermentation
• Fermentation yields small amount of ATP (2)
• Partial oxidation of carbon atoms (6 C ? 3 C)
• Respiration
• Substrate molecules are completely oxidized to
  C02 (6 C ? 1 C)
• Far higher yield of ATP (36)
• The Krebs Cycle and Electron Transport Chain

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Final Electron Acceptors Aerobic respiration,
anaerobic respiration, and fermentation have
different final electron acceptors
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Microbe Growth

• Binary or transverse fission
• Generation or Doubling Time the time required
  for parent cell to form two new daughter cells.

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Microbe Growth

• Lag new cells require adjustment and
  enlargement. The cells are not multiplying
  rapidly.
• Log or exponential maximum rate of growth

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Microbe Growth 2

• Stationary death and multiplication balance
  out. Depleted nutrients and waste buildup.
• Death limiting factors intensify. May last a
  long time.

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Calculating Growth of Cells
Nf Final population Ni Initial
population 2n cells in generation n
generation number
Nf (Ni)2n
Use the table in the handout from the Talaro
Appendix A-2 to calculate the number of cells in
the generation.
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Measuring Growth Serial Dilutions, Plate Counts
and Turbidity
Measuring growth turbidity plate counts
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Calculation of the number of bacteria per
milliliter of culture using serial dilution
Pour plate made by first adding 1.0ml of
diluted culture to 9ml of molten agar Spread
plate made by adding 0.1ml of diluted culture
to surface of solid medium
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Counting colonies using a bacterial colony counter
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Bacterial colonies viewed through the magnifying
glass against a colony-counting grid
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Countable number of colonies (30 to 300 per
plate)
Which of these plates would be the correct one to
count? Why?
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The Petroff-Hausser Counting Chamber
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Turbidity, or a cloudy appearance, is an
indicator of bacterial growth in urine in the
tube on the left
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A Spectrophotometer This instrument can be used
to measure bacterial growth by determining the
degree of light transmission through the culture
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The Streak Plate Method uses agar plates to
prepare pure cultures
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A Streak Plate of Serratia marcescens. Note the
greatly reduced numbers of growth /colonies in
each successive region
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Types of Culture Media

• Natural Media In nature, many species of
  microorganisms grow together in oceans, lakes,
  and soil and on living or dead organic matter
• Synthetic medium A medium prepared in the
  laboratory from material of precise or reasonably
  well-defined composition
• Complex medium contains reasonably familiar
  material but varies slightly in chemical
  composition from batch to batch (e.g. peptone, a
  product of enzyme digestion of proteins)

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Commonly Used Media

• Yeast Extract
• Casein Hydrolysate
• Serum
• Blood agar
• Chocolate agar

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Selective, Differential, and Enrichment Media

• Selective medium encourages growth of some
  organisms but suppresses growth of others
• (e.g. antibiotics)
• Differential medium contains a constituent that
  causes an observable change (e.g. MacConkey agar)
• Enrichment medium contains special nutrients
  that allow growth of a particular organism that
  might not otherwise be present in sufficient
  numbers to allow it to be isolated and identified

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Three species of Candida can be differentiated in
mixed culture when grown on CHROMagar Candida
plates
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Identification of urinary tract pathogens with
differential media (CHROMagar)
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Ecological Associations
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Symbiosis (Mutualism)

• Obligatory
• Both organisms benefit.
• Examples algae fungus lichen, termites and
  trychonympha (a protist)

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Symbiosis (Commensalism)

• One organism benefits and the other is not
  harmed.
• Examples Non-pathogenic bacteria on our skin
  satellitism between bacteria colonies.

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Symbiosis (Parasitism)

• One organism benefits and the other is harmed.
• Examples Pathogenic organisms on their host.
  Plasmodium vivax a protozoan parasite causing
  malaria.

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Non Symbiotic (Synergism)
Substance A

• Free living organisms.
• Both benefit
• The relationship is optional.
• Examples Shared metabolism nitrogen fixing
  bacteria in the soil and plants

Microorganism 1
Substance B
Microorganism 2
Substance C
Microorganism 3
End Product used by all three microorganisms
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Non Symbiotic (Antagonism)

• Free living organisms
• Organisms compete for resources.
• One organism secretes a substance toxic to the
  other.
• Example Ruminal cellulose digesting bacteria
  and fungi

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End of Microbial Nutrition Slides