Microbial Growth and Metabolism

Mixed Population The variety of microbial organisms that make up most environments on earth are part of a mixed population. Mixed microbial population living in a biofilm.

Pure 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

Colony 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 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 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 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

Metabolism 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 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 Growth Nutritional requirements Oxygen requirements Chemical requirements Temperature requirements pH requirements Light requirements

Photosynthesis Photosynthetic organisms capture the energy of sunlight and store it in the form of glucose The overall equation for photosynthesis is: 6 CO 2 + 6H 2 O  C 6 H 12 O 6 + 6H 2 O

Glucose 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 Breakdown The overall equation for the complete breakdown of glucose is: C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ATP The main stages of glucose metabolism are: – Glycolysis – Cellular respiration

Overview of Glucose Breakdown - 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 Breakdown If oxygen is absent fermentation occurs – pyruvate is converted into either lactate, or into ethanol and CO 2 If oxygen is present cellular respiration occurs

Overview of Glucose Breakdown- 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

Glycolysis

Fermentation

Reactions in Mitochondrial Matrix (Eukaryotes) or Cytoplasm (Prokaryotes)

Cellular Respiration Bacterial Cell. Plasma membrane morayeel.louisiana.edu Eukaryotic Cell. Inner mitochondrial membrane

Electron Transport Chain Most of the energy in glucose is stored in electron carriers NADH and FADH 2 – Only 4 total ATP produced per glucose after complete breakdown in the Krebs Cycle

Electron Transport Chain NADH and FADH 2 deposit electrons into electron transport chains in the inner mitochondrial membrane Electrons join with oxygen gas and hydrogen ions to make H 2 O at the end of the ETCs

The End