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Microbiology Chapter 5 Microbial Nutrition & Growth
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7/14/2019 Chapter 5 Microbial Nutrition & Growth.ppt
http://slidepdf.com/reader/full/chapter-5-microbial-nutrition-growthppt 1/54
© 2012 Pearson Education Inc.
Lecture prepared by Mindy Miller-Kittrell North Carolina State University
Chapter 6
Microbial
Nutrition and
Growth
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Growth Requirements
• Microbial growth
– Increase in a population of microbes
• Result of microbial growth is discrete colony
– An aggregation of cells arising from single parentcell
• Reproduction results in growth
© 2012 Pearson Education Inc.
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Growth Requirements
• Organisms use a variety of nutrients for
their energy needs and to build organic
molecules and cellular structures
•Most common nutrients containnecessary elements such as carbon,
oxygen, nitrogen, and hydrogen
• Microbes obtain nutrients from variety of
sources
© 2012 Pearson Education Inc.
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Growth Requirements
• Nutrients: Chemical and Energy Requirements
– Sources of carbon, energy, and electrons
– Two groups of organisms based on source of carbon
– Autotrophs
– Heterotrophs
– Two groups of organisms based on source of energy
– Chemotrophs
–Phototrophs
© 2012 Pearson Education Inc.
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Figure 6.1 Four basic groups of organisms
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Growth Requirements
• Nutrients: Chemical and Energy Requirements
– Oxygen requirements
– Oxygen is essential for obligate aerobes
–Oxygen is deadly for obligate anaerobes
– How can this be true?
– Toxic forms of oxygen are highly reactive and
excellent oxidizing agents
–Resulting oxidation causes irreparable damage tocells
© 2012 Pearson Education Inc.
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Growth Requirements
• Nutrients: Chemical and Energy Requirements
– Oxygen requirements
– Four toxic forms of oxygen
–Singlet oxygen
– Superoxide radicals
– Peroxide anion
– Hydroxyl radical
© 2012 Pearson Education Inc.
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Figure 6.2 Catalase test
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Growth Requirements
• Nutrients: Chemical and Energy Requirements
– Oxygen requirements
– Aerobes
–
Anaerobes – Facultative anaerobes
– Aerotolerant anaerobes
– Microaerophiles
© 2012 Pearson Education Inc.
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Figure 6.3 Oxygen requirements of organisms-overview
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Growth Requirements
• Nutrients: Chemical and Energy Requirements
– Nitrogen requirements
– Anabolism often ceases because of insufficientnitrogen
– Nitrogen acquired from organic and inorganicnutrients
– All cells recycle nitrogen from amino acids andnucleotides
–Nitrogen fixation by certain bacteria is essential to lifeon Earth
© 2012 Pearson Education Inc.
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Growth Requirements
• Nutrients: Chemical and Energy Requirements
– Other chemical requirements
– Phosphorus
– Sulfur
– Trace elements
– Required only in small amounts
– Growth factors
– Necessary organic chemicals that cannot be
synthesized by certain organisms
© 2012 Pearson Education Inc.
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Growth Requirements
• Physical Requirements
– Temperature
– Effect of temperature on proteins
–Effect of temperature on membranes of cells andorganelles
– If too low, membranes become rigid and fragile
– If too high, membranes become too fluid
© 2012 Pearson Education Inc.
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Figure 6.4 Microbial growth-overview
Fi 6 5 F t i f i b b d t t f th
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Figure 6.5 Four categories of microbes based on temperature ranges for growth
Psychrophiles
Mesophiles
Thermophiles
Hyperthermophiles
G r o w
t h r a t e
Temperature (°C)
Fi 6 6 A l f h hil i
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Figure 6.6 An example of psychrophile- overview
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Growth Requirements
• Physical Requirements
– pH
– Organisms are sensitive to changes in acidity
– H+ and OH – interfere with H bonding
– Neutrophiles grow best in a narrow rangearound neutral pH
– Acidophiles grow best in acidic habitats
– Alkalinophiles live in alkaline soils and water
© 2012 Pearson Education Inc.
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Growth Requirements
• Physical Requirements
– Physical effects of water
– Microbes require water to dissolve enzymes and
nutrients – Water is important reactant in many metabolic
reactions
– Most cells die in absence of water
–Some have cell walls that retain water
– Endospores and cysts cease most metabolic activity
– Two physical effects of water
– Osmotic pressure
–Hydrostatic pressure
© 2012 Pearson Education Inc.
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Growth Requirements
• Physical Requirements
– Physical effects of water
– Osmotic pressure
–Pressure exerted on a semipermeable membrane bya solution containing solutes that cannot freely cross
membrane
– Hypotonic solutions have lower solute concentrations
– Hypertonic solutions have greater solute
concentrations
– Restricts organisms to certain environments
– Obligate and facultative halophiles
© 2012 Pearson Education Inc.
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Growth Requirements
• Physical Requirements
– Physical effects of water
– Hydrostatic pressure
–Water exerts pressure in proportion to itsdepth
– Barophiles live under extreme pressure
– Their membranes and enzymes depend on
pressure to maintain their shape
© 2012 Pearson Education Inc.
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Growth Requirements
• Associations and Biofilms
– Organisms live in association with different species
– Antagonistic relationships
–Synergistic relationships
– Symbiotic relationships
© 2012 Pearson Education Inc.
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Growth Requirements
• Associations and Biofilms
– Biofilms
– Complex relationships among numerousmicroorganisms
–Develop an extracellular matrix
– Adheres cells to one another
– Allows attachment to a substrate
– Sequesters nutrients
–May protect individuals in the biofilm
– Form on surfaces often as a result of quorumsensing
– Many microorganisms more harmful as part of a
biofilm© 2012 Pearson Education Inc.
Figure 6 7 Plaque (biofilm) on a human tooth
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Figure 6.7 Plaque (biofilm) on a human tooth
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Culturing Microorganisms
• Inoculum introduced into medium
– Environmental specimens
– Clinical specimens
–Stored specimens
• Culture
– Act of cultivating microorganisms or the
microorganisms that are cultivated
© 2012 Pearson Education Inc.
Figure 6.8 Characteristics of bacterial colonies-overview
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Figure 6.8 Characteristics of bacterial colonies overview
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Culturing Microorganisms
• Obtaining Pure Cultures
– Cultures composed of cells arising from a single
progenitor
–
Progenitor is termed a CFU – Aseptic technique prevents contamination of
sterile substances or objects
– Two common isolation techniques
–Streak plates
– Pour plates
© 2012 Pearson Education Inc.
Figure 6.9 Streak plate method of isolation-overview
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Figure 6.9 Streak plate method of isolation overview
Figure 6.10 Pour plate method of isolation-overview
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g p
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Culturing Microorganisms
• Culture Media
– Majority of prokaryotes have not been grownin culture medium
– Six types of general culture media
– Defined media
– Complex media
– Selective media
– Differential media
– Anaerobic media
– Transport media
© 2012 Pearson Education Inc.
Figure 6.11 Slant tube containing solid media
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g g
Slant
Butt
Figure 6.12 An example of the use of a selective medium
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Fungal coloniesBacterial colonies
pH 7.3 pH 5.6
Figure 6.13 The use of blood agar as a differential medium
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Beta-hemolysis
Alpha-hemolysis
No hemolysis
(gamme-hemolysis)
Figure 6.14 The use of carbohydrate utilization tubes as differential media
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No fermentation Acid fermentation
with gas
Durham tube(inverted tubeto trap gas)
Figure 6.15 Use of MacConkey agar as a selective and differential medium-overview
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Figure 6.16 An anaerobic culture system
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Clamp
Chamber
Petri plates
Airtight lid
Envelopecontainingchemicals torelease CO2
and H2
Palladium pelletsto catalyze reactionremoving O2
Methylene blue(anaerobicindicator)
C lt i Mi i
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Culturing Microorganisms
• Special Culture Techniques
– Techniques developed for culturing
microorganisms
–
Animal and cell culture – Low-oxygen culture
– Enrichment culture
© 2012 Pearson Education Inc.
C lt i Mi i
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Culturing Microorganisms
• Preserving Cultures
– Refrigeration
– Stores for short periods of time
–Deep-freezing – Stores for years
– Lyophilization
– Stores for decades
© 2012 Pearson Education Inc.
G th f Mi bi l P l ti
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Growth of Microbial Populations
ANIMATION Bacterial Growth: Overview
© 2012 Pearson Education Inc.
Growth of Microbial Populations
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Growth of Microbial Populations
© 2012 Pearson Education Inc.
ANIMATION Binary Fission
Figure 6.17 Binary fission events-overview
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Figure 6.18 Comparison of arithmetic and logarithmic growth-overview
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Growth of Microbial Populations
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Growth of Microbial Populations
• Generation Time
– Time required for a bacterial cell to grow
and divide
–
Dependent on chemical and physicalconditions
© 2012 Pearson Education Inc.
Figure 6.19 Two growth curves of logarithmic growth-overview
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Figure 6.20 Typical microbial growth curve
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Stationary phase
Death(decline)phaseLog
(exponential)phase
Lag phase
Time
N u m b e r o f l i v e c e l l s ( l o g )
Growth of Microbial Populations
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Growth of Microbial Populations
© 2012 Pearson Education Inc.
ANIMATION Bacterial Growth Curve
Figure 6.21 Schematic of chemostat
F h di ith
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Fresh medium witha limiting amountof a nutrient
Sterile air of other gas
Culture
Culturevessel
Flow-rateregulator
Overflowtube
Growth of Microbial Populations
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Growth of Microbial Populations
• Measuring Microbial Reproduction
– Direct methods
– Serial dilution and viable plate counts
–
Membrane filtration – Most probable number
– Microscopic counts
– Electronic counters
© 2012 Pearson Education Inc.
Figure 6.22 Estimating microbial population size-overview
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Figure 6.23 Use of membrane filtration to estimate microbial population-overview
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Figure 6.24 The most probable number (MPN) method for estimating microbial numbers
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1.0 ml 1.0 ml
1:1001:10Undiluted
Inoculate 1.0 ml intoeach of 5 tubes
Phenol red, pHcolor indicator,added
Incubate
Results
4 tubes positive 2 tubes positive 1 tube positive
Figure 6.25 The use of a cell counter for estimating microbial numbers-overview
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Growth of Microbial Populations
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Growth of Microbial Populations
• Measuring Microbial Growth
– Indirect methods
– Metabolic activity
–
Dry weight – Turbidity
© 2012 Pearson Education Inc.
Figure 6.26 Spectrophotometry-overview
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Growth of Microbial Populations
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Growth of Microbial Populations
• Measuring Microbial Reproduction
– Genetic methods
– Isolate DNA sequences of unculturable
prokaryotes
– Used to estimate the number of these
microbes