Download Microbial nutrition

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
• 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
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•
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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
glucose
NAD+
ADP
NADH + H+
ATP
C3H4O3
pyruvic acid
Substrate-level phosphorylation
CH2
ADP
ATP
CH3
COPO3H2
C
COOH
COOH
phosphoenol
pyruvic acid
O
pyruvic acid
Fermentation products
• Need to regenerate NAD+
• Reduce pyruvic acid
NADH + H+
C3H4O3
pyruvic acid
NAD+
C3H5O3
lactic acid
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.