Chapter 5 Microbial Nutrition & Growth.ppt

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



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




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




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




Figure 6.1 Four basic groups of organisms



Growth 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




Growth Requirements



– Four toxic forms of oxygen

–Singlet oxygen

– Superoxide radicals

– Peroxide anion

– Hydroxyl radical




Figure 6.2 Catalase test



Growth Requirements



– Aerobes

–

Anaerobes – Facultative anaerobes

– Aerotolerant anaerobes

– Microaerophiles




Figure 6.3 Oxygen requirements of organisms-overview



Growth 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




Growth 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




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




Figure 6.4 Microbial growth-overview

Fi 6 5 F t i f i b b d t t f th



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



Figure 6.6 An example of psychrophile- overview



Growth 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




Growth 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




Growth Requirements



– 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




Growth Requirements



– 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




Growth Requirements

• Associations and Biofilms

– Organisms live in association with different species

– Antagonistic relationships

–Synergistic relationships

– Symbiotic relationships




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



Figure 6.7 Plaque (biofilm) on a human tooth



Culturing Microorganisms

• Inoculum introduced into medium

– Environmental specimens

– Clinical specimens

–Stored specimens

• Culture

– Act of cultivating microorganisms or the

microorganisms that are cultivated


Figure 6.8 Characteristics of bacterial colonies-overview



Figure 6.8 Characteristics of bacterial colonies overview




• 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


Figure 6.9 Streak plate method of isolation-overview



Figure 6.9 Streak plate method of isolation overview

Figure 6.10 Pour plate method of isolation-overview



g p




• 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


Figure 6.11 Slant tube containing solid media



g g

Slant

Butt

Figure 6.12 An example of the use of a selective medium



Fungal coloniesBacterial colonies

pH 7.3 pH 5.6

Figure 6.13 The use of blood agar as a differential medium



Beta-hemolysis

Alpha-hemolysis

No hemolysis

(gamme-hemolysis)

Figure 6.14 The use of carbohydrate utilization tubes as differential media



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



Figure 6.16 An anaerobic culture system



Clamp

Chamber

Petri plates

Airtight lid

Envelopecontainingchemicals torelease CO2

and H2

Palladium pelletsto catalyze reactionremoving O2

Methylene blue(anaerobicindicator)

C lt i Mi i




• Special Culture Techniques

– Techniques developed for culturing

microorganisms

–

Animal and cell culture – Low-oxygen culture

– Enrichment culture


C lt i Mi i




• Preserving Cultures

– Refrigeration

– Stores for short periods of time

–Deep-freezing – Stores for years

– Lyophilization

– Stores for decades


G th f Mi bi l P l ti



Growth of Microbial Populations

ANIMATION Bacterial Growth: Overview



http://localhost/var/www/apps/conversion/tmp/scratch_4/bacterial_growth.html





ANIMATION Binary Fission

Figure 6.17 Binary fission events-overview

http://localhost/var/www/apps/conversion/tmp/scratch_4/binary_fission.html



Figure 6.18 Comparison of arithmetic and logarithmic growth-overview







• Generation Time

– Time required for a bacterial cell to grow

and divide

–

Dependent on chemical and physicalconditions


Figure 6.19 Two growth curves of logarithmic growth-overview



Figure 6.20 Typical microbial growth curve



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 )






ANIMATION Bacterial Growth Curve

Figure 6.21 Schematic of chemostat

F h di ith

http://localhost/var/www/apps/conversion/tmp/scratch_4/bacterial_growth_curve.html



Fresh medium witha limiting amountof a nutrient

Sterile air of other gas

Culture

Culturevessel

Flow-rateregulator

Overflowtube





• Measuring Microbial Reproduction

– Direct methods

– Serial dilution and viable plate counts

–

Membrane filtration – Most probable number

– Microscopic counts

– Electronic counters


Figure 6.22 Estimating microbial population size-overview



Figure 6.23 Use of membrane filtration to estimate microbial population-overview



Figure 6.24 The most probable number (MPN) method for estimating microbial numbers



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







• Measuring Microbial Growth

– Indirect methods

– Metabolic activity

–

Dry weight – Turbidity


Figure 6.26 Spectrophotometry-overview







• Measuring Microbial Reproduction

– Genetic methods

– Isolate DNA sequences of unculturable

prokaryotes

– Used to estimate the number of these

microbes

Documents

Chapter 5 Microbial Nutrition & Growth.ppt