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Microbial Nutrition Cell metabolism. Nutritional Categories of Microorganisms. Microorganisms are often grouped according to the sources of energy they use: Phototrophs use light as an energy source Photosynthesis Chemotrophs use chemicals as energy sources Chemoorganotroph - PowerPoint PPT Presentation
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Microbial NutritionCell metabolism
Nutritional Categories of Microorganisms
• Microorganisms are often grouped according to the sources of energy they use:
– Phototrophs use light as an energy source• Photosynthesis
– Chemotrophs use chemicals as energy sources• Chemoorganotroph
• Chemolithotroph
Biochemical Components of Cells
• Water: 80 % of wet weight
• Dry weight– Protein 40-70 %– Nucleic acid 13-34%– Lipid 10-15 %– Also monomers, intermediates and inorganic
ions
Macronutrients
• Cells make proteins, nucleic acids and lipids
• Macronutrients– macromolecules, metabolism– C, H, O, N, S, P, K, Mg, Fe– Sources
• Organic compounds
• Inorganic salts
Micronutrients
• Elements needed in trace quantities – Co, Cu, Mn, Zn, V– Enzymes– tap water
• Growth factors– Organic compounds– Vitamins
Defined / Complex Media
• Defined– Prepared with precise amounts of chemicals– Known composition
• Complex– Exact composition unknown– Digests of beef, soybean, yeast
Other Culturing Considerations
• pH• Oxygen concentration• Temperature• Light / carbon dioxide (phototrophic organisms)
Role of Oxygen in Nutrition
• Obligate aerobes – require O2
• Obligate anaerobes – O2 is toxic
• Facultative anaerobes
• Microaerophilic organisms
Transport of Nutrients into the Cell
• Nutrients are obtained from the environment
• Many of the nutrients are polar
• Cannot diffuse across the cell membrane
• Proteins embedded in the membrane
• Transport against a concentration gradient - active transport
Bioenergetics
• Living cells require energy for growth, biosynthesis, reproduction and transport
• Energy needed to drive the biochemical reactions of cells is stored and transferred via adenosine triphosphate (ATP)
Fermentation and Respiration
• Chemoorganotrophs obtain their energy from oxidation of organic compounds– loss of electrons/removal of hydrogen
• Fermentation– No terminal electron acceptor
• Respiration– Terminal electron acceptor (e.g. O2)
Glycolysis
C6H12O6
C3H4O3
glucose
pyruvic acid
ADP
ATP
NAD+
NADH + H+
Substrate-level phosphorylation
CH2
COPO3H2
COOH
CH3
C
COOH
O
ADP ATP
phosphoenolpyruvic acid
pyruvic acid
Fermentation products
• Need to regenerate NAD+
• Reduce pyruvic acid
C3H4O3 C3H5O3
pyruvic acid lactic acid
NADH + H+ NAD+
Oxidative phosphorylation
• Occurs in respiration (aerobic and anaerobic)
• Proton motive force– Electrons from NADH are passed along an
electron transport chain– Protons are pumped across membrane– Electrochemical gradient– Drives ATP synthesis from ADP and Pi
Summary
• Nutrients– Macronutrients/micronutrients– Defined/complex media– Cell membranes
• Energy production– Different modes
Further reading
Madigan MT, JM Martinko, J Parker, 2000. Brock Biology of Microorganisms, 9th Edition. Chapters 3 and 4.