2 - metabolism and growth
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Copyright © 2010 Pearson Education, Inc.
Metabolism and Growth
Copyright © 2010 Pearson Education, Inc.
Requirements for Growth: chemical
NOT COPS
N Organic growth factors Trace elements
C O P S
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What is the function of carbon, nitrogen, sulfur, phosphorus and trace elements?
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Chemical Requirements
Carbon Structural organic molecules, energy source Chemoheterotrophs use organic carbon sources Autotrophs use CO2
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Chemical Requirements
Nitrogen In amino acids and proteins Most bacteria decompose proteins Some bacteria use NH4+ or NO3–
A few bacteria use N2 in nitrogen fixation
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Chemical Requirements
Sulfur In BAT: Biotin, amino acids, and protein
Phosphorus In DNA, RNA, ATP, and membranes
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Chemical Requirements
Trace elements Inorganic elements required in small amounts Usually as enzyme cofactors
Copyright © 2010 Pearson Education, Inc. Table 6.1
The Effect of Oxygen (O2) on Growth
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Organic Growth Factors
Where are organic growth factors obtained? from the environment
What are organic growth factors involved with? Vitamins, amino acids, purines, and pyrimidines
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Catabolic and Anabolic Reactions
Metabolism: The sum of the chemical reactions in an organism
catabolism, require water: cells break down sugars
anabolism, dehydration synthesis: formation of proteins from amino acids
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Catabolic and Anabolic Reactions
A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell A - B, B - C, C - D A cannot make D
Metabolic pathways are determined by enzymes
Enzymes are encoded by genes
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Enzymes
Proteins Biological catalysts Produced by living cells Catalyze chemical reactions by lowering activation
energy Speed up a chemical reaction without being
permanently altered
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Enzyme Components
Biological catalysts Speed up a chemical reaction without being altered Are specific (active site) – act on specific substance
(substrate) Crucial function: speed up biochemical reactions at a temp
which is compatible with a living, normal functioning cell
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Factors influencing Enzymatic Activity
Temperature pH Substrate concentration Inhibitors
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Inhibitors
Function: control bacteria by control of enzymes
Competitive – compete with the normal substrate for the active site shape and chemical structure are similar to normal
substrate Ex. Sulfa drug
Noncompetitive – interact with another part of the enzyme, changes shape = nonfunctional
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Carbohydrate Catabolism
The breakdown of carbohydrates to release energy Glucose most commonly used carbohydrate Glycolysis: breaking down glucose to pyruvic
acid
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Carbohydrate Catabolism
Glycolysis: glucose broken down Leads into cellular respiration (aerobic/anaerobic)
or fermentation
Aerobic Anaerobic Fermentation
Krebs cycle: high energy
Part of Krebs cycle: low energy
No Krebs
Electron transport chain
Electron Transport chain
No ETC
Final Acceptor: O2
Final acceptor: does not use O2
Various organic end products
Inorganic product
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Metabolic Diversity among Organisms
Photoautotrophs Photoheterotrophs Chemoautotrophs Chemoheterotrophs
Autotrophs – fix carbon Heterotrophs – cannot fix carbon Chemotrophs – energy from oxidation Phototrophs – energy from light
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The Requirements for Growth: Physical
Physical requirements Temperature pH Osmotic pressure
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Physical Requirements
Temperature Minimum growth temperature Optimum growth temperature Maximum growth temperature
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Temperature
Three primary Groups
1.Psychrophiles – cold loving
2.Mesophiles – moderate
3.Thermophiles – heat loving
Copyright © 2010 Pearson Education, Inc. Figure 6.1
Typical Growth Rates and Temperature
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Psychrotrophs
Grow between 0°C and 20–30°C Cause food spoilage
Copyright © 2010 Pearson Education, Inc. Figure 6.2
Food Preservation Temperatures
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pH
Most bacteria grow between pH 6.5 and 7.5 Molds and yeasts grow between pH 5 and 6 Acidophiles grow in acidic environments
Copyright © 2010 Pearson Education, Inc. Figure 6.5
Biofilms
Microbial communities Form slime or
hydrogels Form on teeth, contact
lenses and catheters
Copyright © 2010 Pearson Education, Inc. Applications of Microbiology, p. 57
Biofilms
Share nutrients Sheltered from
harmful factors 70% bacterial
infections are from biofilms
100X more resistant to antibiotics than free swimming microbes
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Agar
Complex polysaccharide Used as solidifying agent for culture media in Petri
plates, slants, and deeps Generally not metabolized by microbes Liquefies at 100°C Solidifies at ~40°C
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Culture Media
Chemically defined media: Exact chemical composition is known
Complex media: Extracts and digests of yeasts, meat, or plants Nutrient broth Nutrient agar
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Anaerobic Culture Methods
Reducing media Contain chemicals (thioglycolate or oxyrase) that combine
O2
Heated to drive off O2
Used to grow anaerobes
Copyright © 2010 Pearson Education, Inc. Figure 6.7
An Anaerobic Chamber
Copyright © 2010 Pearson Education, Inc. Figure 6.10
Selective Media
Suppress unwanted microbes and encourage desired microbes
Copyright © 2010 Pearson Education, Inc. Figure 6.9
Differential Media
Make it easy to distinguish colonies of different microbes.
Copyright © 2010 Pearson Education, Inc. Figure 6.11
The Streak Plate Method
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Preserving Bacterial Cultures
Deep-freezing: –50° to –95°C Lyophilization (freeze-drying): Frozen (–54° to –
72°C) and dehydrated in a vacuum
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Measuring Microbial Growth
Direct Methods Plate counts Filtration MPN Direct microscopic count
Indirect Methods Turbidity Metabolic activity Dry weight
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Standard plate count Viable count
Microscopic count No incubation time
Growth phase gram + is suseptible to penic. LOG phase
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