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Microbial Nutrition and GrowthMicrobial Nutrition and Growth
Sofronio Agustin
Professor
Sofronio Agustin
Professor
LECTURES IN MICROBIOLOGYLECTURES IN
MICROBIOLOGY
LESSON 5LESSON 5
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Lesson 5 TopicsLesson 5 Topics
Microbial Nutrition
Environmental Factors
Microbial Growth
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Microbial NutritionMicrobial Nutrition
Based on intake:
(a) Macronutrients (CHONPS)
(b) Micronutrients (trace elements)
Based on carbon content:
(a) Organic nutrients- contain carbon
(b) Inorganic nutrients- simple atom or molecule without carbon
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Chemical CompositionChemical Composition
Bacteria are composed of different elements and molecules, with water (70%) and proteins (15%) being the most abundant.
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Essential NutrientsEssential Nutrients
Carbon sourceEnergy SourceGrowth Factors
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Carbon SourceCarbon Source
Autotrophs - obtain carbon from inorganic molecules like CO2
Heterotrophs - obtain carbon from organic matter from other life forms(e.g. sugar, proteins and lipids)
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Energy SourceEnergy Source
Photoautotrophs and photoheterotrophs obtain energy from sunlight
Chemoautotrophs derive electron energy from reduced inorganic compounds
Chemoheterotrophs obtain electron energy from hydrogen atoms of organic compounds
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Nutritional CategoriesNutritional Categories
Summary of different
nutritional categories of
microbes based energy
and carbon sources
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MethanogensMethanogens
Methanogens are
chemoautotrophic
microbes
Example: methane
producing Archaea
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Extracellular Digestion Extracellular Digestion
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Cell MembraneCell Membrane
Phospholipid bilayer with integral and peripheral proteins
“Fluid mosaic” model - phospholipids and proteins move
laterallyExhibits “selective permeability”
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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Membrane Transport Membrane Transport
Passive:(a) Simple diffusion
(b) Facilitated diffusion
(c) Osmosis
Active:(a) Permease
(b) Group translocation
(c) Endocytosis
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Simple DiffusionSimple Diffusion
Net movement of solute from area of high
concentration to a low concentrated area
No energy is expended
Down the concentration gradient (like a
river flowing downstream)
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DiffusionDiffusion
A cube of sugar will
diffuse from a
concentrated area
into a more dilute
region, until an
equilibrium is
reached.
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Facilitated DiffusionFacilitated Diffusion
Transport of polar molecules and ions across the membrane down their concentration gradients
No energy is expended (passive)Carrier protein facilitates the binding and
transport -Specificity-Saturation-Competition
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Facilitated DiffusionFacilitated Diffusion
Facilitated Diffusion: The Process
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OsmosisOsmosis
Diffusion of solvent (usually, water) through a permeable but selective membrane
Water tends to move toward higher solute concentrated areas
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Tonicity Tonicity
Fate of cells in different osmotic conditions - isotonic, hypotonic, and hypertonic solutions
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Active Transport Active Transport
Transport of molecules against its concentration gradientRequires energy and transport protein
(Ex. Permeases and protein pumps transport sugars, amino acids, organic acids, phosphates and metal ions)
Group translocation transports and modifies specific sugars
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Endocytosis Endocytosis
Large substances are taken in by the cell but are not transported through the membrane.
Requires energy (active)Common in eukaryotes
- Phagocytosis
- Pinocytosis
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Active TransportActive Transport
Example of permease, group translocation and endocytosis
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Cellular Transport : Summary Cellular Transport : Summary
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Environmental Factors Environmental Factors
Temperature Gas pH Osmotic pressure Other factors Microbial association
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TemperatureTemperature
Psychrophiles – (cold loving) 0 to 15 °CPsychrotrophs - (food spoilage) grow
between 20 to 30 °CMesophiles- (most human pathogens)
20 to 40 °CThermophiles- (heat loving) 45 to 80 °CThemoduric - (contaminants of heated food)
survive in short exposures to high tempHyperthermophiles - (Archaea)
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Temperature ToleranceTemperature Tolerance
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Gas RequirementsGas Requirements
Two gases that influence microbial growth:
(1) Oxygen Respiration - terminal electron acceptor Oxidizing agent - toxic forms
(2) Carbon dioxide
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Oxygen MetabolitesOxygen Metabolites
Superoxide radical - O2 -
Singlet oxygen - O2 with single electron in its
valence shell
H2O2
All are toxic byproducts of metabolism neutralized by
enzymes SOD (superoxide dismutase), peroxidase and
catalase.
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Bacterial Types Bacterial Types
Obligate aerobe
Facultative anaerobe
Obligate anaerobe
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Obligate AerobesObligate Aerobes
Require oxygen for metabolism Possesses enzymes that can neutralize
the toxic oxygen metabolites:
SOD, peroxidase and catalase
Ex: Most fungi, protozoa, and bacteria like Bacillus sp. and Pseudomonas sp.
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Obligate AnaerobesObligate Anaerobes
Cannot use oxygen for metabolism
Do not possess SOD and catalase
The presence of oxygen is toxic to
the cell
Ex: Clostridium sp. and Bacteroides sp.
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AnaerobiosisAnaerobiosis
Anaerobic culture techniques: (a) anaerobic chamber, (b) anaerobic jar
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Facultative AnaerobesFacultative Anaerobes
Does not require oxygen for metabolism, but can grow in its presence
During minus oxygen states, anaerobic respiration or fermentation occurs
Possess superoxide dismutase and catalase
Ex. E. coli and S. aureus
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Thioglycolate BrothThioglycolate Broth
Thioglycollate broth is used to demonstrate aerotolerance of bacteria.
Aerobes, facultative anaerobes, and obligate anaerobes can be detected using this medium.
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Other Gas RequirementsOther Gas Requirements
Microaerophiles - requires less than 10% of atmospheric O2.
Ex: Campylobacter jejuni
Capnophiles - requires increased CO2 (5-15%) tension for initial growth.
Ex: S. pneumoniae
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pH pH
Most cells grow best between pH 6-8
Acidophiles (up to pH 0) - molds and
yeast
Alkalinophiles (up pH 10) urea-
decomposing bacteria like Proteus sp.
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Osmotic PressureOsmotic Pressure
Osmophiles - live in solutions with high solute concentration (e.g. sugar content in jams)
Halophiles - requires high salt concentrations andwithstands hypertonic conditionsEx. Halobacterium sp. (Archaea)
Facultative halophiles - can survive high salt conditions but is not required for survival
Ex. Staphylococcus aureus
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Other Factors Other Factors
Radiation- withstand UV, infrared rays
Barophiles – withstand high pressures
Spores and cysts- can survive dry
habitats
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Microbial Interactions Microbial Interactions
Influence microorganisms have on other microbes:
Symbiotic relationshipNon-symbiotic relationship
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Symbiotic RelationshipSymbiotic Relationship
Organisms that live together in close nutritional relationships
Types: Mutualism – both organism benefit
Commensalism – only one organisms benefits
Parasitism – typically host-microbe relationship
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CommensalismCommensalism
“Satellitism” as a form of commensalism
Staphylococcus aureus provides vitamins and amino acids to Haemophilus influenzae, which grows around colonies of S. aureus.
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Non-Symbiotic RelationshipsNon-Symbiotic Relationships
Organisms are free-living, and do not rely on each other for survival
Types: Synergism – shared metabolism
enhances growth of both microbes Antagonism- competition between
microorganisms
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Microbe-Host InteractionsMicrobe-Host Interactions
Can be commensal, parasitic, and synergistic
Ex. E. coli produce vitamin K for the host
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Microbial GrowthMicrobial Growth
Binary fission
Generation time
Growth curve
Enumeration of bacteria
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Binary FissionBinary Fission
Parent cell enlarges and duplicates its DNA
Septum formation divides the cell into two
separate chambers
Complete division results in two identical
daughter cells
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Steps in Binary FissionSteps in Binary Fission
Rod-shaped bacteria undergoing binary fission
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Growth CurveGrowth Curve
Lag phaseLog phaseStationary phaseDeath phase
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Phases of Bacterial GrowthPhases of Bacterial Growth
Growth curve in a bacterial culture.
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Enumeration of BacteriaEnumeration of Bacteria
Direct Methods:
(a) Microscopic
(b) Viable plate count
(c) Membrane filtration
(d) Most probable number Indirect Methods:
(a) Turbidity (b) Metabolic assay(c) Dry weight determinations
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Direct Microscopic CountDirect Microscopic Count
The direct cell method counts the total dead and live cells in a special microscopic slide containing a premeasured grid. Petroff-Hausser counting chamber used in dairy industry.
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Standard Plate CountStandard Plate Count
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Serially diluted samples are plated out and bacterial count expressed in CFU/ml.
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Membrane FiltrationMembrane Filtration
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Membrane filtration and coliform counts.
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TurbidimetricTurbidimetric
Turbidimetric measurements as indicators of bacterial growth.The greater the turbidity the larger the population density.
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Coulter CounterCoulter Counter
The Coulter Counter
uses an electronic
sensor to detect and
count the number of
cells.
Rapid automated
counting method