Copyright © 2013 Pearson Education, Inc. Lectures prepared by Christine L. Case Chapter 6 Microbial Growth © 2013 Pearson Education, Inc. Lectures prepared by Christine L. Case * © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Microbial GrowthIncrease in number of cells, not cell sizePopulationsColonies * © 2013 Pearson Education, Inc. The Requirements for GrowthPhysical requirementsTemperaturepHOsmotic pressureChemical requirementsCarbonNitrogen, sulfur, and phosphorousTrace elementsOxygenOrganic growth factor * © 2013 Pearson Education, Inc. Physical RequirementsTemperatureMinimum growth temperatureOptimum growth temperatureMaximum growth temperature * © 2013 Pearson Education, Inc. Figure 6.1 Typical growth rates of different types of microorganisms in response to temperature. Psychrophiles Psychrotrophs Mesophiles Thermophiles Hyperthermophiles © 2013 Pearson Education, Inc. Applications of Microbiology 6.1 A white microbial biofilm is visible on this deep-sea hydrothermal vent. Water is being emitted through the ocean floor at temperatures above 100°C. © 2013 Pearson Education, Inc. PsychrotrophsGrow between 0°C and 20–30°CCause food spoilage * © 2013 Pearson Education, Inc. Figure 6.2 Food preservation temperatures. Temperatures in this range destroy most microbes, although lower temperatures take more time. Very slow bacterial growth. Rapid growth of bacteria; some may produce toxins. Many bacteria survive; some may grow. Refrigerator temperatures; may allow slow growth of spoilage bacteria, very few pathogens. No significant growth below freezing. Danger zone © 2013 Pearson Education, Inc. Figure 6.3 The effect of the amount of food on its cooling rate in a refrigerator and its chance of spoilage. Refrigerator air 5 cm (2′′) deep 15 cm (6′′) deep Approximate temperature range at which Bacillus cereus multiplies in rice © 2013 Pearson Education, Inc. pHMost bacteria grow between pH 6.5 and 7.5Molds and yeasts grow between pH 5 and 6Acidophiles grow in acidic environments * © 2013 Pearson Education, Inc. Osmotic PressureHypertonic environments, or an increase in salt or sugar, cause plasmolysisExtreme or obligate halophiles require high osmotic pressureFacultative halophiles tolerate high osmotic pressure * © 2013 Pearson Education, Inc. Figure 6.4 Plasmolysis. Plasma membrane Cell wall Cytoplasm H2O NaCl 10% Cytoplasm Plasma membrane Cell in isotonic solution. Plasmolyzed cell in hypertonic solution. NaCl 0.85% © 2013 Pearson Education, Inc. Chemical RequirementsCarbonStructural organic molecules, energy sourceChemoheterotrophs use organic carbon sourcesAutotrophs use CO2 * © 2013 Pearson Education, Inc. Chemical RequirementsNitrogenIn amino acids and proteinsMost bacteria decompose proteinsSome bacteria use NH4+ or NO3–A few bacteria use N2 in nitrogen fixation * © 2013 Pearson Education, Inc. Chemical RequirementsSulfurIn amino acids, thi.

1. Copyright © 2013 Pearson Education, Inc.
Lectures prepared by Christine L. Case
Chapter 6
Microbial Growth
© 2013 Pearson Education, Inc.
Lectures prepared by Christine L. Case
*
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
Microbial GrowthIncrease in number of cells, not cell
sizePopulationsColonies
*
© 2013 Pearson Education, Inc.

2. The Requirements for GrowthPhysical
requirementsTemperaturepHOsmotic pressureChemical
requirementsCarbonNitrogen, sulfur, and phosphorousTrace
elementsOxygenOrganic growth factor
*
© 2013 Pearson Education, Inc.
Physical RequirementsTemperatureMinimum growth
temperatureOptimum growth temperatureMaximum growth
temperature
*
© 2013 Pearson Education, Inc.
Figure 6.1 Typical growth rates of different types of
microorganisms in response to temperature.
Psychrophiles
Psychrotrophs
Mesophiles
Thermophiles
Hyperthermophiles
© 2013 Pearson Education, Inc.
Applications of Microbiology 6.1 A white microbial biofilm is

3. visible on this deep-sea hydrothermal vent. Water is being
emitted through the ocean floor at temperatures above 100°C.
© 2013 Pearson Education, Inc.
PsychrotrophsGrow between 0°C and 20–30°CCause food
spoilage
*
© 2013 Pearson Education, Inc.
Figure 6.2 Food preservation temperatures.
Temperatures in this range destroy most microbes,
although lower temperatures take more time.
Very slow bacterial growth.
Rapid growth of bacteria; some may produce toxins.
Many bacteria survive; some may grow.
Refrigerator temperatures; may allow slow growth
of spoilage bacteria, very few pathogens.
No significant growth below freezing.
Danger zone
© 2013 Pearson Education, Inc.
Figure 6.3 The effect of the amount of food on its cooling rate
in a refrigerator and its chance of spoilage.
Refrigerator air
5 cm (2′′) deep
15 cm (6′′) deep
Approximate temperature

4. range at which Bacillus cereus multiplies in rice
© 2013 Pearson Education, Inc.
pHMost bacteria grow between pH 6.5 and 7.5Molds and yeasts
grow between pH 5 and 6Acidophiles grow in acidic
environments
*
© 2013 Pearson Education, Inc.
Osmotic PressureHypertonic environments, or an increase in
salt or sugar, cause plasmolysisExtreme or obligate halophiles
require high osmotic pressureFacultative halophiles tolerate
high osmotic pressure
*
© 2013 Pearson Education, Inc.
Figure 6.4 Plasmolysis.
Plasma
membrane
Cell wall
Cytoplasm
H2O
NaCl 10%

5. Cytoplasm
Plasma
membrane
Cell in isotonic solution.
Plasmolyzed cell in hypertonic solution.
NaCl 0.85%
© 2013 Pearson Education, Inc.
Chemical RequirementsCarbonStructural organic molecules,
energy sourceChemoheterotrophs use organic carbon
sourcesAutotrophs use CO2
*
© 2013 Pearson Education, Inc.
Chemical RequirementsNitrogenIn amino acids and
proteinsMost bacteria decompose proteinsSome bacteria use
NH4+ or NO3–A few bacteria use N2 in nitrogen fixation
*
© 2013 Pearson Education, Inc.
Chemical RequirementsSulfurIn amino acids, thiamine, and
biotinMost bacteria decompose proteinsSome bacteria use
SO42– or H2SPhosphorus In DNA, RNA, ATP, and
membranesPO43– is a source of phosphorus

6. *
© 2013 Pearson Education, Inc.
Chemical RequirementsTrace elementsInorganic elements
required in small amountsUsually as enzyme cofactors
*
© 2013 Pearson Education, Inc.
Table 6.1 The Effect of Oxygen on the Growth of Various Types
of Bacteria
© 2013 Pearson Education, Inc.
Singlet oxygen: 1O2− boosted to a higher-energy
stateSuperoxide free radicals: O2
Peroxide anion: O22–
Hydroxyl radical (OH•)
Toxic Oxygen
Superoxide dismutase

7. O2 + O2 + 2 H+
H2O2 + O2
Catalase
2 H2O2
2 H2O + O2
Peroxidase
H2O2 + 2 H+
2 H2O
*
© 2013 Pearson Education, Inc.
Organic Growth FactorsOrganic compounds obtained from the
environmentVitamins, amino acids, purines, and pyrimidines
*
© 2013 Pearson Education, Inc.
BiofilmsMicrobial communitiesForm slime or hydrogelsBacteria
attracted by chemicals via quorum sensing

8. *
© 2013 Pearson Education, Inc.
Figure 6.5 Biofilms.
Clumps of bacteria adhering to surface
Surface
Water currents
Migrating clump of bacteria
© 2013 Pearson Education, Inc.
BiofilmsShare nutrientsSheltered from harmful factors
*
© 2013 Pearson Education, Inc.
Applications of Microbiology 3.2 Pseudomonas aeruginosa
biofilm.
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
BiofilmsPatients with indwelling catheters received
contaminated heparinBacterial numbers in contaminated heparin
were too low to cause infection84–421 days after exposure,
patients developed infections

9. *
© 2013 Pearson Education, Inc.
Culture MediaCulture medium: nutrients prepared for microbial
growthSterile: no living microbesInoculum: microbes being
introduced into mediumInoculation: the process of introducing
microbes into a mediumCulture: microbes growing in/on culture
medium
*
© 2013 Pearson Education, Inc.
AgarComplex polysaccharide Used as solidifying agent for
culture media in Petri plates, slants, and deepsGenerally not
metabolized by microbesLiquefies at 100°CSolidifies at ~40°C
*
© 2013 Pearson Education, Inc.
Culture MediaChemically defined media: exact chemical
composition is knownComplex media: extracts and digests of
yeasts, meat, or plantsNutrient brothNutrient agar

10. *
© 2013 Pearson Education, Inc.
Table 6.2 A Chemically Defined Medium for Growing a Typical
Chemoheterotroph, Such as Escherichia coli
© 2013 Pearson Education, Inc.
Table 6.3 Defined Culture Medium for Leuconostoc
mesenteroides
© 2013 Pearson Education, Inc.
Table 6.4 Composition of Nutrient Agar, a Complex Medium for
the Growth of Heterotrophic Bacteria
© 2013 Pearson Education, Inc.
Anaerobic Culture MethodsReducing mediaContain chemicals
(thioglycolate or oxyrase) that
combine O2Heated to drive off O2
*
© 2013 Pearson Education, Inc.

11. Figure 6.6 A jar for cultivating anaerobic bacteria on Petri
plates.
Lid with
O-ring gasket
Envelope containing sodium bicarbonate and sodium
borohydride
Anaerobic indicator (methylene blue)
Petri plates
Clamp with clamp screw
Palladium catalyst pellets
© 2013 Pearson Education, Inc.
Figure 6.7 An anaerobic chamber.
Arm ports
Air
lock
© 2013 Pearson Education, Inc.
CapnophilesMicrobes that require high CO2 conditionsCO2
packetCandle jar
*
© 2013 Pearson Education, Inc.
BSL-1: no special precautionsBSL-2: lab coat, gloves, eye
protectionBSL-3: biosafety cabinets to prevent airborne
transmissionBSL-4: sealed, negative pressureExhaust air is
filtered twice

12. Biosafety Levels
*
© 2013 Pearson Education, Inc.
Figure 6.8 Technicians in a biosafety level 4 (BSL-4)
laboratory.
© 2013 Pearson Education, Inc.
Make it easy to distinguish colonies of different microbes
Differential Media
*
© 2013 Pearson Education, Inc.
Figure 6.9 Blood agar, a differential medium containing red
blood cells.
Bacterial colonies
Hemolysis
© 2013 Pearson Education, Inc.
Suppress unwanted microbes and encourage desired microbes
Selective Media

13. *
© 2013 Pearson Education, Inc.
Figure 6.10 Differential medium.
Uninoculated
Staphylococcus
epidermis
Staphylococcus
aureus
© 2013 Pearson Education, Inc.
Enrichment CultureEncourages growth of desired
microbeAssume a soil sample contains a few phenol-
degrading bacteria and thousands of
other bacteriaInoculate phenol-containing culture medium with
the soil, and incubateTransfer 1 ml to another flask of the
phenol medium, and incubateTransfer 1 ml to another flask of
the phenol medium, and incubateOnly phenol-metabolizing
bacteria will be growing
*
© 2013 Pearson Education, Inc.
Obtaining Pure CulturesA pure culture contains only one
species or strainA colony is a population of cells arising from a
single cell or spore or from a group of attached cellsA colony is
often called a colony-forming unit (CFU)The streak plate

14. method is used to isolate pure cultures
*
© 2013 Pearson Education, Inc.
Figure 6.11 The streak plate method for isolating pure bacterial
cultures.
Colonies
1
2
3
© 2013 Pearson Education, Inc.
Preserving Bacterial CulturesDeep-freezing: –50° to –
95°CLyophilization (freeze-drying): frozen
(–54° to –72°C) and dehydrated in a vacuum
*
© 2013 Pearson Education, Inc.
Binary fissionBuddingConidiospores
(actinomycetes)Fragmentation of filaments
ANIMATION Bacterial Growth: Overview
Reproduction in Prokaryotes

15. *
© 2013 Pearson Education, Inc.
Figure 6.12a Binary fission in bacteria.
Cell elongates and DNA is replicated.
Cell wall and plasma membrane begin to constrict.
Cross-wall forms, completely separating the two DNA copies.
Cells separate.
Cell wall
Plasma membrane
DNA (nucleoid)
(a) A diagram of the sequence of cell division
© 2013 Pearson Education, Inc.
Figure 6.12b Binary fission in bacteria.
(b) A thin section of a cell of Bacillus licheniformis starting to
divide
Cell wall
DNA (nucleoid)
Partially formed cross-wall
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
Figure 6.13a Cell division.
© 2013 Pearson Education, Inc.

16. Figure 6.13b Cell division.
© 2013 Pearson Education, Inc.
If 100 cells growing for 5 hours produced
1,720,320 cells:
ANIMATION Binary Fission
Generation Time
Number of generations =
Log number of cells (end) − Log number of cells (beginning)
0.301
60 min × hours
Number of generations
Generation time =
= 21 minutes/generation
*
© 2013 Pearson Education, Inc.
Figure 6.14 A growth curve for an exponentially increasing
population, plotted logarithmically (dashed line) and
arithmetically (solid line).
Log10 = 1.51
Log10 = 3.01
Log10 = 4.52
Log10 = 6.02
(1,048,576)
Generations

17. Log10 of number of cells
Number of cells
(32)
(1024)
(32,768)
(65,536)
(131,072)
(262,144)
(524,288)
© 2013 Pearson Education, Inc.
Lag Phase
Intense activity preparing for population growth, but no
increase in population.
Log Phase
Logarithmic, or exponential, increase in population.
Stationary Phase
Period of equilibrium; microbial deaths balance production of
new cells.
Death Phase
Population Is decreasing at a logarithmic rate.
The logarithmic growth in the log phase is due to reproduction
by binary fission (bacteria) or mitosis (yeast).
Figure 6.15 Understanding the Bacterial Growth Curve.
Staphylococcus spp.
© 2013 Pearson Education, Inc.
Figure 6.16 Serial dilutions and plate counts.
Original inoculum
1 ml
1 ml
1 ml

18. 1 ml
1 ml
9 m broth
in each tube
Dilutions
1:10
1:100
1:1000
1:10,000
1:100,000
1 ml
1 ml
1 ml
1 ml
1 ml
1:10
1:100
1:1000
1:10,000
1:100,000
(10-1)
(10-2)
(10-3)
(10-4)
(10-5)
Plating
Calculation: Number of colonies on plate × reciprocal of
dilution of sample = number of bacteria/ml
(For example, if 54 colonies are on a plate of 1:1000 dilution,
then the count is 54 × 1000 = 54,000 bacteria/ml in sample.)
© 2013 Pearson Education, Inc.
After incubation, count colonies on plates that have
25–250 colonies (CFUs)

19. Plate Counts
*
© 2013 Pearson Education, Inc.
Figure 6.17 Methods of preparing plates for plate counts.
The pour plate method
The spread plate method
Inoculate empty plate.
Add melted nutrient agar.
Swirl to mix.
Colonies grow on and in solidified medium.
1.0 or 0.1 ml
0.1 ml
Bacterial dilution
Inoculate plate containing solid medium.
Spread inoculum over surface evenly.
Colonies grow only on surface of medium.
© 2013 Pearson Education, Inc.
Figure 6.18 Counting bacteria by filtration.
© 2013 Pearson Education, Inc.
Multiple tube MPN testCount positive tubes
Most Probable Number
*

20. © 2013 Pearson Education, Inc.
Figure 6.19a The most probable number (MPN) method.
Volume of Inoculum for Each Set of Five Tubes
(a) Most probable number (MPN) dilution series.
© 2013 Pearson Education, Inc.
Compare with a statistical table
Most Probable Number
*
© 2013 Pearson Education, Inc.
Figure 6.19b The most probable number (MPN) method.
(b) MPN table.
© 2013 Pearson Education, Inc.
Figure 6.20 Direct microscopic count of bacteria with a Petroff-
Hausser cell counter.
Grid with 25 large squares
Cover glass
Slide
Bacterial suspension is added here and fills the shallow volume
over the squares by capillary action.
Bacterial suspension
Cover glass
Slide

21. Cross section of a cell counter.
The depth under the cover glass and the area of the squares are
known, so the volume of the bacterial suspension over the
squares can be calculated (depth × area).
Microscopic count: All cells in several large squares are
counted, and the numbers are averaged. The large square shown
here has 14 bacterial cells.
The volume of fluid over the
large square is 1/1,250,000
of a milliliter. If it contains 14 cells, as shown here, then
there are 14 × 1,250,000 = 17,500,000 cells in a milliliter.
Location of squares
© 2013 Pearson Education, Inc.
Direct Microscopic Count
Number of bacteria/ml =
Number of cells counted
Volume of area counted
14
8 × 10−7
= 17,500,000
*
© 2013 Pearson Education, Inc.
Figure 6.21 Turbidity estimation of bacterial numbers.
Light source
Light

22. Blank
Spectrophotometer
Light-sensitive detector
Scattered light that does not reach detector
Bacterial suspension
© 2013 Pearson Education, Inc.
Measuring Microbial Growth
Direct MethodsPlate countsFiltrationMPNDirect microscopic
count
Indirect MethodsTurbidityMetabolic activityDry weight
*
Chapter 12 Review
Vocabulary
1. Arthropods
2. Helminthes
3. Fungi
4. Algae
5. Protozoa
6. Hyphae
7. Thallus
8. Mycology
9. Eukaryotic
10. Sterols
11. Endospores
12. Vegetative
13. Septa
14. Mold
15. Mycelium
16. Yeast

23. 17. Aerial hyphae
18. Dimorphism
19. Fission yeast
20. Sexual spores
21. Asexual spores
22. Conidiospores
23. Conidia
24. Conidiophore
25. Arthroconidia
26. Blastoconidia
27. Sporangiospore
28. Plasmogamy
29. Karyogamy
30. Meiosis
31. Aerobic
32. Anaerobic
33. Mycosis
34. Systemic mycoses
35. Subcutaneous mycoses
36. Dermatophytes
37. Cutaneous mycoses
38. Superficial mycoses
39. Opportunistic pathogen
40. List three positive effects of fungus
41. List three negative effects of fungus
42. Lichen
43. Unicellular
44. Multicellular
45. Flagella
46. Schizogony
47. Conjugation
48. Gametes
49. Encystment
50. Oocyst
51. Cystotome
52. Vacuoles

24. 53. Anal pore
54. Hemoflagellates
55. Amebae
56. Pseudopods
57. Ciliates
58. Slime mold
59. Cytoplasmic streaming
60. Larval stage
61. Diocious
62. Monoecious
63. Flatworm
64. Fluke
65. Tapeworm
66. roundworms
67. Intermediate host
68. Definitive host
69. Scolex
70. Proglottids
71. Cysticerci
72. Hydatid cyst
73. Spicules
74. Sexual dimorphism
75. Vector
Chapter 11 Summary
You are required to know all of the vocabulary listed in the list,
all concepts in red and the general characteristics of all the
organisms in red.
Vocabulary:
1. Oxygenic
2. Budding
3. Anoxyhenic
4. Host
5. Anaerobic
6. Prosthecae

25. 7. Aerobic
8. Coccus
9. Facultative anaerobes
10. Gram positive
11. Septicemia
12. Gram negative
13. Opportunistic
14. Coccobacillus
15. Pathogen
16. Fermentation
17. Obligate
18. Endosymbiosis
19. Parasite
20. Heterotrophs
21. Autotrophs
22. Enterics
23. Photoautotrophs
24. Elementary bodies
25. Chemoheterotrophs
26. Heterocysts
27. Flagella
28. Glycocalyx
29. Peritrichous
30. Morphology
31. Reticulate body
32. Axial filament
33. Endospore
34. Filamentous
35. Pleomorphic
36. Dimorphic
37. Acid-fast stain
38. Motile
Prokaryotes
· Daomains
· Archaea (know the definition of each of these terms)

26. · Hyperthermophiles
· Halophyles
· Thermophiles
· Methanogens
· Bacteria (know what each of these classifications entails)
· Gram Positive
· Gram Negative
_____________________________________________________
_____________________________
BACTERIA
· Humana pathogens
· Obligate intracellular parasites (ICP)- (know what it means to
be an ICP)
· Cause Spotted Fevers
· Ricketsia
· Does NOT cause Spotted Fevers
· Erlichia
· Survive in phagocytes (WBC’s) but not ICP
· Brucella
· Do not Survive in phagocytes (WBC’s) but not ICP
· Bartonella
· Those that live in insects
· Wolbochia
· Do not live in insects
· Have prosthecae (stalks)
· Cellular appendages that are neither pili nor flagella, as they
are extensions of the cellular membrane and contain cytosol.
One notable group of prosthecates is the genus Caulobacter.
· Hyphomicrobium
·
Gram Negative Bacteria
· Proteobacteria
· Largest taxonomic group of bacteria
· Includes most of the G(-) bacteria
· Separated into 5 classes
· Alphaproteobacteria

27. · Rickettsia
· Ehrlichia
· Rhizobium
· Caulobacter
· Bortanella
· Brucella
· Wolbachia
· Betaproteobacteria
· Spirillum
· Burkholderia
· Bortadella
· Sphaerotilus
· Gammaproteobacteria
· Pseudomonadales
· Moraxella
· Legionalla
· Coxiella
· Vibrio
· Enterics
· Salmonella
· Escherichia
· Shigella
· Serratia
· Klebsiella
· Yersenia
· Erwinia
· Proteus
· Enterobacter
· Pasteuralles
· Pasteurella
· Haemophilus
· Deltaproteobacteria
· Desulfovibrionales
· Myxococcales
· Epsilonproteobacteria
· Campylobacter

28. · Helicobacter
· Nonproteobacteria
· Cyanobacteria
· Anoxygenic Bacteria
· Chlamydiae
· Planctomycetes
· Bacteroidetes
· Fusobacteria
· Spirochetes
· Treponema
· Borrelia
· Leptospira
· Deinococci
Gram Positive Bacteria
· Firmicutes
· Clostridiales
· Epulopiscium
· Bacillales
· Bacillus
· Staphylococcus
· Lactobacillales
· Lactobacillus
· Streptococcus
· Enterococcus
· Listeria
· Mycoplasmatales
· Mycoplasma
· Mycoplasma pneumonia
· Actinobacteria (High G+C)
· Mycobacterium
· Corynebacteruium
· Propionibacterium
· Gardenerella
· Frankia
· Streptomyces

29. · Actinomyces
· Nocardia
Domain Archaea (know the generalities of the domain)
· Extremophiles
· Thermophiles
· Methanogens
· Hyperthermophiles
· Halophiles