1. Microbiology: A Systems Approach
PowerPoint to accompany
Microbiology: A Systems Approach
Cowan/Talaro
Chapter 7
Elements of Microbial Nutrition, Ecology, and Growth
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Chapter 7 Topics Microbial Nutrition Transport Across the Membrane
Environmental Factors
Microbial Growth

3. Table 7.1

4. Microbial Nutrition Definitions Nutrition Essential nutrient
Macronutrient
Micronutrient
Inorganic nutrient
Organic nutrient

5. Bacteria are composed of different elements and molecules, with water (70%) and proteins (15%) being the most abundant.
Table 7.2 Analysis of the chemical composition
of an E. coli cell.

6. Sources of essential nutrients
Required for metabolism and growth
Carbon source
Energy source

7. Carbon source Heterotroph (depends on other life forms)
Organic molecules
Ex. Sugars, proteins, lipids
Autotroph (self-feeders)
Inorganic molecules
Ex. CO2

8. Sources of Essential Nutrients
Nitrogen
Oxygen
Hydrogen
Phosphorous
Sulfur

9. Miscellaneous Nutrients
Mineral Ions
K, Na, Ca, Mg, Z
Trace Elements
Cu, Co, Ni, Mb, Mn, Si, B, I
Growth Factors

10. Growth factors Essential organic nutrients
Not synthesized by the microbe, and must be supplemented
Ex. Amino acids, vitamins

11. Nutritional Types Carbon Source Energy Source Organic – “Hetero”
Inorganic – “Auto”
Energy Source
Light – “Photo”
Chemical – “Chemo”

12. Energy source Photoautotrophs Chemoautotrophs Photoheterotrophs
Chemoheterotrophs

13. Photoautotroph Derive their energy from sunlight
Transform light rays into chemical energy
Primary producers of organic matter for heterotrophs
Primary producers of oxygen
Ex. Algae, plants, cyanobacteria

14. Fig. 4.27b

15. Chemoautotrophs Carbon Source is Inorganic ( CO2) Two types
Chemical Energy can be organic or inorganic
Ex. Methanogens, Lithoautotrophs

16. Methanogens are an example of a chemoautotroph.
Fig. 7.1 Methane-producing archaea

17. Photoheterotrophs Light energy Organic Carbon Source
Purple & Green Photosyntheic Bacteria

18. Fig. 4.28

19. Chemoheterotrophs Derive both carbon and energy from organic compounds
Saprobic
decomposers of plant litter, animal matter, and dead microbes
Parasitic
Live in or on the body of a host

20. Representation of a saprobe and its mode of action.
Fig. 7.2 Extracellular digestion in a saprobe with a cell wall.

21. Summary of the different nutritional categories based on carbon and energy source.
Table 7.3 Nutritional categories of microbes by energy
and carbon source.

22. Transport mechanisms Osmosis Passive Transport Active transport
Simple Diffusion
Facilitated Diffusion
Active transport
Endocytosis

23. Osmosis Diffusion of water through a permeable but selective membrane
Water moves toward the higher solute concentrated areas
Isotonic
Hypotonic
Hypertonic

24. Representation of the osmosis process.
Fig. 7.3 Osmosis, the diffusion of water through a selectively
permeable membrane

25. Cells with- and without cell walls, and their responses to different osmotic conditions (isotonic, hypotonic, hypertonic).
Fig. 7.4 Cell responses to solutions of differing osmotic content.

26. Fig. 7.4

27. Fig. i7.p211a

28. Diffusion
Net movement of molecules from a high concentrated area to a low concentrated area
No energy is expended (passive)
Concentration gradient and permeability affect movement

29. A cube of sugar will diffuse from a concentrated area into a more dilute region, until an equilibrium is reached.
Fig. 7.5 Diffusion of molecules in aqueous solutions

30. Facilitated diffusion
Transport of polar molecules and ions across the membrane
No energy is expended (passive)
Carrier protein facilitates the binding and transport
Specificity
Saturation
Competition

31. Representation of the facilitated diffusion process.
Fig. 7.6 Facilitated diffusion

32. Active transport Transport of molecules against a gradient
Requires energy (active)
Requires a transport protein
sugars, amino acids, organic acids, phosphates and metal ions.

33. Fig. 7.7a

34. Fig. 7.7b

35. Endocytosis
Substances are taken in, but are not transported through the membrane.
Requires energy (active)
Common for eucaryotes
Phagocytosis – solid particles
Pinocytosis - liquids

36. Fig. 7.7c

37. Example of the permease, group translocation, and endocytosis processes.
Fig. 7.7 Active transport

38. Summary of the transport processes in cells.
Table 7.4 Summary of transport processes in cells

39. Environmental Factors
Temperature
Gas pH
Osmotic pressure
Other environmental factors
Microbial associations

40. Temperature For optimal growth and metabolism
Psychrophile – to 15 °C
Psychrotrophs – °C
Mesophile to 40 °C
Thermophile- 45 to 80 °C
Hyperthermophiles - > 80° C

41. Growth and metabolism of different ecological groups based on ideal temperatures.
Fig. 7.8 Ecological groups by temperature

42. Example of a psychrophilic photosynthetic Red snow organism.
Fig. 7.9 Red snow

43. Gas Two gases that most influence microbial growth Oxygen
Respiration
Oxidizing agent
Carbon dioxide

44. Oxidizing agent Oxygen metabolites are toxic
Singlet Oxygen
Superoxide Free Radicals
Hydrogen Peroxide
Hydroxyl Radicals
These toxic metabolites must be neutralized for growth

45. Five categories of bacteria
Obligate aerobe
Facultative anaerobe
Obligate anaerobe
Aerotolerant Anaerobes
Microaerophiles

46. Obligate aerobe Requires oxygen for metabolism
Possess enzymes that can neutralize the toxic oxygen metabolites
Superoxide dismutase and catalase
Ex. Most fungi, protozoa, and bacteria

47. Facultative anaerobe
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. Gram negative pathogens

48. Obligate anaerobes Cannot use oxygen for metabolism
Do not possess superoxide dismutase and catalase
The presence of oxygen is toxic to the cell

49. Aerotolerant Anaerobes
Can tolerate oxygen but don’t use it for growth

50. Microaerophiles Require Oxygen, but only in small amounts
Don’t make enough enzymes to detoxify toxic forms of oxygen if they are exposed to normal atmosphere

51. Anaerobes must grow in an oxygen minus environment, because toxic oxygen metabolites cannot be neutralized.
Fig Culturing technique for anaerobes

52. Thioglycollate broth enables the identification of aerobes, facultative anaerobes, and obligate anaerobes.
Reducing Media
Fig Use of thioglycollate broth to demonstrate
oxygen requirements.

53. Fig. 7.10b

54. pH Cells grow best between pH 6-8
Exceptions would be acidophiles (pH 0), and alkalinophiles (pH 10).

55. Osmotic pressure Halophiles Withstand hypertonic conditions
Some requires high salt concentrations
Ex. Halobacterium
Some can survive high salt conditions but is not required
Ex. Staphylococcus aureus

56. Other factors
Radiation- Spores or pigments help withstand UV, infrared
Barophiles – withstand high pressures
Spores and cysts- can survive dry habitats

57. Ecological association
Influence microorganisms have on other microbes
Symbiotic relationship
Non-symbiotic relationship

58. Symbiotic Organisms that live in close nutritional relationship Types
Mutualism – both organism benefit
Commensalism – one organisms benefits
Parasitism – host/microbe relationship

59. An example of commensalism, where Staphylococcus aureus provides vitamins and amino acids to Haemophilus influenzae.
Fig Satellitism, a type of commensalism

60. Non-symbiotic
Organisms are free-living, and do not rely on each other for survival
Types
Synergism – shared metabolism, not required
Antagonism- competition between microorganisms

61. Interrelationships between microbes and humans
Can be commensal, parasitic, and synergistic
Normal Microbial Flora are beneficial
Mutualistic
Ex. E. coli produce vitamin K for the host

62. Microbial Growth Binary fission Generation time Growth curve
Enumeration of bacteria

63. Binary fission The division of a bacterial cell
Parental cell enlarges and duplicates its DNA
Septum formation divides the cell into two separate chambers
Complete division results in two identical cells

64. Representation of the steps in binary fission of a rod-shaped bacterium.
Fig Steps in binary fission of a rod-shaped bacterium.

65. Generation time
The time required for a complete division cycle (doubling)
Length of the generation time is a measure of the growth rate
Exponentials are used to define the numbers of bacteria after growth

66. Representation of how a single bacterium doubles after a complete division, and how this can be plotted using exponentials.
Fig The mathematics of population growth

67. Fig. 7.14b

68. Growth curve
Lag phase
Log phase
Stationary phase
Death phase

69. Lag phase
Cells are adjusting, enlarging, and synthesizing critical proteins and metabolites
Not doubling at their maximum growth rate

70. Log phase Maximum exponential growth rate of cell division
Adequate nutrients
Favorable environment

71. Stationary phase
Survival mode – depletion in nutrients, released waste can inhibit growth
When the number of cells that stop dividing equal the number of cells that continue to divide

72. Death phase
A majority of cells begin to die exponentially due to lack of nutrients
A chemostat will provide a continuous supply of nutrients, thereby the death phase is never achieved.

73. The four main phases of growth in a bacterial culture.
Fig The growth curve in a bacterial culture.

74. Measuring Microbial Growth
Direct Methods
Plate Counts
Direct cell count
Automated devices
Coulter counter
Flow cytometer
Indirect Methods
Turbidity
Spectrophotometer
Measure Metabolic Activity

75. Fig. i7.6

76. The direct cell method counts the total dead and live cells in a special microscopic slide containing a premeasured grid.
Fig Direct microscopic count of bacteria.

77. A Coulter counter uses an electronic sensor to detect and count the number of cells.
Fig Coulter counter

78. The greater the turbidity, the larger the population size.
Fig Turbidity measurements as indicators of growth