Microbial GrowthMicrobial Growth and Metabolism and Metabolism

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.

microvet.arizona.edu

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

GlycolysisGlycolysis

FermentationFermentation

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

The EndThe End