Mixed PopulationMixed PopulationThe variety of microbial organisms that
make up most environments on earth are part of a mixed population.
Mixed microbial population living in a biofilm. www.epscor.dbi.udel.edu
Pure CulturePure Culture
Separating the progeny (offspring) of a single bacterial cell from all other bacteria.
A culture that contains only a single strain of an organism.
diverge.hunter.cuny.edu
ColonyColony
Colony– A population of cells that arise from a single
bacterial cell in one spot.– About 1 million cells are required for a colony
to be easily seen with the naked eye.
biology.clc.uc.edu
Open System vs. Closed SystemOpen System vs. Closed System
Open System– Organisms that grow in nature.– Nutrients replenished and wastes removed.
Closed System– In the lab (i.e. agar plates, broth tubes).– Nutrients will run out and wastes are not
removed.
Generation TimeGeneration Time
Generation Time– The time it takes one cell to undergo binary
fission or to divide into two cells.Exponential Growth
– Occurs during a rapidly multiplying bacterial population.
– Occurs when each cell gives rise to 2 cells, each of which divides into 2 more, yielding a total of 4, and so on.
Dynamics of Bacterial GrowthDynamics of Bacterial Growth
Lag Phase– Cell division does not occur immediately.– Cells must increase in length and synthesize
macromolecules needed for protein synthesis and enzymes for cell division.
Exponential Phase– Cells divide at a constant rate.
Stationary Phase– Cell division decreases and the total number of cells remains
constant.
Death Phase– Total number of viable cells decreases exponentially.
MetabolismMetabolism
Metabolism– All the chemical reactions that occur within the
cell.
2 types of metabolic reactions:– Catabolism
Break large molecules into smaller molecules. Acquire energy.
– Anabolism Build large molecules from small molecules. Takes energy.
Classifying Microbes According to Classifying Microbes According to Their Energy and Carbon Sources.Their Energy and Carbon Sources.
Based on energy source– Phototrophs
Use light as an energy source; photosynthesize.
– Chemotrophs Use inorganic and organic chemicals.
Based on carbon source– Autotrophs
Use carbon dioxide.
– Heterotrophs Do not use carbon dioxide as their carbon source.
Microbial GrowthMicrobial Growth
Nutritional requirementsOxygen requirementsChemical requirementsTemperature requirementspH requirementsLight requirements
PhotosynthesisPhotosynthesis
Photosynthetic organisms capture the energy of sunlight and store it in the form of glucose
The overall equation for photosynthesis is:
6 CO2 + 6H2O C6H12O6 + 6H2O
GlucoseGlucose
Glucose is a key energy-storing molecule:– Nearly all cells metabolize glucose for energy– Glucose metabolism is fairly simple– Other organic molecules are converted to glucose for
energy harvesting
Overview of Glucose Overview of Glucose BreakdownBreakdown
The overall equation for the complete breakdown of glucose is:
C6H12O6 + 6O2 6CO2 + 6H2O + ATP
The main stages of glucose metabolism are:– Glycolysis– Cellular respiration
Overview of Glucose Overview of Glucose Breakdown - GlycolysisBreakdown - Glycolysis
Glycolysis– Occurs in the cytosol – Does not require oxygen– Breaks glucose into pyruvate– Yields two molecules of ATP per molecule of
glucose
Overview of Glucose BreakdownOverview of Glucose Breakdown
If oxygen is absent fermentation occurs– pyruvate is converted into either lactate, or into
ethanol and CO2
If oxygen is present cellular respiration occurs
Overview of Glucose Overview of Glucose Breakdown- Cellular RespirationBreakdown- Cellular Respiration
Cellular respiration – Occurs in mitochondria (in eukaryotes)– Occurs in plasma membrane (in prokaryotes)– Requires oxygen– Breaks down pyruvate into carbon dioxide and water– Produces an additional 32 or 34 ATP molecules,
depending on the cell type
Reactions in Reactions in Mitochondrial Matrix (Eukaryotes) Mitochondrial Matrix (Eukaryotes)
or Cytoplasm (Prokaryotes)or Cytoplasm (Prokaryotes)
Cellular RespirationCellular Respiration
Bacterial Cell. Plasma membranemorayeel.louisiana.edu
Eukaryotic Cell. Inner mitochondrial membrane
Electron Transport ChainElectron Transport Chain
Most of the energy in glucose is stored in electron carriers NADH and FADH2
– Only 4 total ATP produced per glucose after complete breakdown in the Krebs Cycle
Electron Transport ChainElectron Transport Chain
NADH and FADH2 deposit electrons into electron transport chains in the inner mitochondrial membrane
Electrons join with oxygen gas and hydrogen ions to make H2O at the end of the ETCs
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