Microbial Nutrition and Growth Sofronio Agustin Professor Sofronio Agustin Professor LECTURES IN MICROBIOLOGY LECTURES IN MICROBIOLOGY LESSON 5.

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”

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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