1. Microbial Nutrition Nutrition: Essential nutrient: Macronutrients:
Nutrients are acquired from the environment and used for cellular activities
Essential nutrient:
Any substance, whether in elemental or molecular form, that must be provided to an organism
Macronutrients:
Required in relatively large quantities
Play principal roles in cell structure and metabolism
Micronutrients (trace elements):
Present in smaller amounts
Involved in enzyme function and maintenance of protein structure

2. Inorganic versus Organic Nutrients
Inorganic nutrients:
Atom or simple molecule that contains a combination of atoms other than carbon and hydrogen
Organic nutrients:
Contain carbon and hydrogen atoms
Usually the product of living things

3. Principal Inorganic Reservoirs of Elements
Carbon— CO 2 in air; CO 3 2− in rocks and sediments
Oxygen— O 2 in air, certain oxides, water
Nitrogen— N 2 in air; NO 3 − , NO 2 − , NH 4 + in soil and water
Hydrogen—Water, H 2 gas, mineral deposits
Phosphorus—Mineral deposits ( PO 4 3− , H 3 PO 4 )
Sulfur—Mineral deposits, volcanic sediments ( SO 4 2− , H 2 S)
Potassium—Mineral deposits, the ocean (KCL, K 3 PO 4 )
Sodium—Mineral deposits, the ocean (NaCl, NaSi)
Calcium—Mineral deposits, the ocean ( CaCO 3 , CaCl 2 )
Magnesium—Mineral deposits, geologic sediments ( MgSO 4 )
Chloride—The ocean (NaCl, NH 4 Cl)
Iron—Mineral deposits, geologic sediments ( FeSO 4 )
Manganese, molybdenum, cobalt, nickel, zinc, copper, other micronutrients— various geologic sediments

4. Analysis of the Chemical Composition of an Escherichia coli Cell
Element
% Dry Weight
Carbon (C) 50
Oxygen (O) 20
Nitrogen (N) 14
Hydrogen (H) 8
Phosphorus (P) 3
Sulfur (S) 1
Potassium (K)
Sodium (Na)
Calcium (Ca)
0.5
Magnesium (Mg)
Chlorine (Cl)
Iron (Fe)
0.2
Trace metals
0.3
Organic Compounds
% Total Weight
% Dry Weight
Proteins 15 50
RNA 6 20
DNA 1 3
Carbohydrates 10
Lipids 2
Miscellaneous 4
Inorganic Compounds
% Total Weight
% Dry Weight
Water 70 -
All others 1 3

5. Carbon Sources: Heterotroph
An organism that must obtain its carbon in organic form
Dependent on other life forms
Most carbon sources exist in a form that is simple enough for absorption
Larger molecules must be digested by the cell before absorption

6. Carbon Sources: Autotroph
“Self-feeder”
Organism that uses inorganic CO 2 as its carbon source
Have the capacity to convert CO 2 into carbon compounds
Not nutritionally dependent on other living things

7. Nitrogen Sources
Main reservoir is nitrogen gas ( N 2 ), 79% of atmosphere
indispensable to structure of proteins, DNA, RNA, and ATP
Primary nitrogen sources for heterotrophs
Must be degraded into basic building blocks in order to be utilized
Some bacteria and algae utilize inorganic nitrogenous nutrients ( NO 3 − , NO 2 − , or NH 3 )
Regardless of the source, nitrogen must be converted to NH 3 before it enters the cell
This is the only form that can be directly combined with carbon to synthesize amino acids and other compounds

8. Oxygen Sources
Oxygen plays an important role in the structural and enzymatic functions of the cell
Major component of carbohydrates, lipids, nucleic acids and proteins
Common component of inorganic salts O 2 makes up 20% of atmosphere

9. Hydrogen Sources Overlapping roles in the biochemistry of cells:
Maintaining pH
Forming hydrogen bonds between molecules
Serving as the source of free energy in oxidation–reduction reactions of respiration

10. Phosphorus (Phosphate) Sources
Main inorganic source is phosphate ( PO 4 3− )
Derived from phosphoric acid ( H 3 PO 4 )
Found in rocks and oceanic mineral deposits
Key component of nucleic acids
Essential to genetics of cells and viruses
Found in ATP, important energy molecule in cells

11. Sulfur Sources
Widely distributed throughout the environment in rocks and sediments
Essential component of some vitamins (vitamin B 1 ) and amino acids methionine and cysteine
Form disulfide bonds that help determine the shape and structural stability of proteins

12. Essential Organic Nutrients
Growth factor:
An organic compound such as an amino acid, nitrogenous base, or vitamin that cannot be synthesized by an organism
Example: essential amino acids
Must be provided by the environment

13. Nutritional Categories of Microbes by Energy and Carbon Source
Category/Carbon Source
Energy Source
Example
Autotroph/ 𝐂𝐎 𝟐
Nonliving Environment
1. Photoautotroph
Sunlight
Photosynthetic organisms, such as algae, plants, cyanobacteria
2. Chemoautotroph
Simple inorganic chemicals
Only certain bacteria or archaea, such as methanogens, deep-sea vent bacteria
Category/Carbon Source
Energy Source
Example
Heterotroph/Organic
Other Organisms or Sunlight
1. Photoheterotroph
Sunlight
Purple and green photosynthetic bacteria
2a. Chemoheterotroph: Parasite
Utilizing the tissues, fluids of a live host
Various parasites and pathogens; can be bacteria, fungi, protozoa, animals
2b. Chemoheterotroph: Saprobe
Metabolizing the organic matter of dead organisms
Fungi, bacteria

14. Aerobic Respiration
Principal energy-yielding pathway in animals, protozoa, fungi, and aerobic bacteria
Complementary to photosynthesis
Glucose and oxygen are reactants, and carbon dioxide is given off
Earth’s balance of energy and metabolic gases is dependent on this reaction

15. Saprobic Microorganisms
Decomposers of plant litter, animal matter, and dead microbes
Important in recycling nutrients held in organic materials
Most saprobes have a rigid cell wall and cannot engulf large particles of food
Bacteria and fungi
Release enzymes into the environment to digest food into smaller particles that can be transported into the cell

16. How Microbes Feed: Nutrient Absorption
Necessary nutrients must be taken into the cell and waste materials must be transported out of the cell
Transport occurs across the cell membrane
Structure specialized for transport
Cell wall is too nonselective to screen the entrance or exit of molecules

17. Diffusion
The movement of molecules in a gradient from an area of higher density or concentration to an area of lower density or concentration
Diffusion across a cell membrane is determined by the concentration gradient and the permeability of the substance
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18. The Movement of Water: Osmosis
Osmosis: The movement of water across a selectively permeable membrane
The membrane is selectively or differentially permeable: has passageways that allow the passage of water but not other dissolved molecules

19. Environmental Factors That Influence Microbes
Heat
Cold
Gases
Acid
Radiation
Osmotic pressure
Hydrostatic pressure
Other microbes

20. Cardinal Temperatures
Cardinal temperatures: range of temperatures for the growth of a given microbial species
Minimum temperature
Maximum temperature
Optimum temperature

21. Minimum and Maximum Temperatures
Minimum temperature:
The lowest temperature that permits a microbe’s continued growth and metabolism
Below this temperature, its activities are limited
Maximum temperature:
Highest temperature at which growth and metabolism can proceed
If the temperature rises slightly above maximum, growth will stop
If the temperature continues to rise, enzymes and nucleic acids will become denatured, or permanently inactivated

22. Optimum Temperature Optimum temperature:
Intermediate temperature range between minimum and maximum
Promotes the fastest rate of growth and metabolism
Small chemical differences in bacterial membranes which affect their fluidity allow them to thrive at different temperatures

23. (a) © Francois Gohier/Science Source; (b) Courtesy Nozomu Takeuchi
Psychrophiles
Organisms that have an optimum temperature below 15°C
Capable of growth at 0°C
Cannot grow above 20°C
Psychrotrophs: grow slowly in the cold, but have an optimum temperature between 15°C and 30°C
(a) © Francois Gohier/Science Source; (b) Courtesy Nozomu Takeuchi
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24. Mesophiles Majority of medically significant organisms
Individual species can grow from 10°C to 50°C
Optimum growth temperature: 20°C to 40°C
Most human pathogens: 30°C to 40°C
Thermoduric microbes survive short exposure to high temperatures; common contaminants of heated or pasteurized foods

25. Thermophiles Grow optimally at temperatures above 45°C
Live in soil and water associated with volcanic activity, compost piles, habitats directly exposed to the sun
General range of growth: 45°C to 80°C
Extreme thermophiles grow between 80°C and 121°C

26. Gases Oxygen has the greatest impact on microbial growth
Microbes fall into one of the three categories:
Those that use oxygen and can detoxify it
Those that can neither use oxygen nor detoxify it
Those that do not use oxygen but can detoxify it

27. Oxygen Requirements Aerobe (aerobic organism): Facultative anaerobe:
Can use gaseous oxygen in its metabolism
Possesses the enzymes needed to process toxic oxygen products
Obligate aerobe: an organism that cannot grow without oxygen
Facultative anaerobe:
An aerobe that does not require oxygen for its metabolism
Capable of growth in the absence of oxygen
Metabolizes by aerobic respiration when oxygen is present
Adopts anaerobic metabolism (fermentation) when oxygen is absent

28. Oxygen Requirements Microaerophile:
Does not grow at normal atmospheric concentrations of oxygen
Requires a small amount of oxygen in its metabolism
Usually live in a habitat that provides a small amount of oxygen but is not directly exposed to the atmosphere
Anaerobe (anaerobic microorganism):
Lacks the metabolic enzyme systems for using oxygen in respiration
Strict or obligate anaerobes cannot tolerate free oxygen and will die in its presence
Live in highly reduced habitats such as lakes, oceans, and soil

29. Culturing Techniques for Anaerobes
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(a) © Hank Morgan/Science Source

30. Oxygen Requirements Aerotolerant anaerobes: Do not utilize oxygen
Can survive and grow to a limited extent in its presence
Not harmed by oxygen because they possess alternative mechanisms for breaking down peroxides and superoxide

31. Carbon Dioxide Requirements
Capnophiles:
Grow best at a higher CO 2 tension than is normally present in the atmosphere
Important in the isolation of some pathogens
Incubation is carried out in a CO 2 incubator that provides 3 to 10% CO 2

32. pH
pH: the degree of acidity or alkalinity of a solution expressed on a scale from 0 to 14
Pure water is neutral at pH 7.0
As the pH value decreases toward 0, acidity increases
As the pH value increases toward 14, alkalinity increases
Obligate acidophiles:
Require an acidic environment for growth
Molds and yeasts tolerate acid and are common spoilage agents of pickled foods
Alkalinophiles:
Live in hot pools and soils that contain high levels of basic minerals
Bacteria that decompose urine create alkaline conditions

33. Symbiosis
Symbiosis: a general term used to denote a situation in which two organisms live together in a close partnership
Mutualism: exists when organisms live in an obligatory but mutually beneficial relationship
© Corbis RF
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34. Symbiosis
Commensalism: relationship benefits one member and not the other
Commensal: receives benefits
Coinhabitant: neither harmed nor benefitted
Parasitism:
Host: provides the parasitic microbe with nutrients and a habitat
Parasite: multiplication of the parasite usually harms the host to some extent

35. Nonsymbiotic Associations
Antagonism:
Arises when members of a community compete
One microbe secretes chemical substances into the surrounding environment that inhibit or destroy other microbes
Synergism:
An interrelationship between two or more free-living organisms that benefits both but is not necessary for their survival
Antibiosis is a form of antagonism:
The production of inhibitory compounds, such as antibiotics

36. Biofilms: The Epitome of Synergy
Biofilms are mixed communities of different kinds of bacteria and other microbes:
Pioneer colonizer initially attaches to a surface
Other microbes attach to the pioneer or to the polymeric or protein substance secreted by the pioneer
Quorum sensing: cells are stimulated to release chemicals as the population grows to monitor its size

37. Biofilms Jump to long description
(a) Courtesy Ellen Swogger and Garth James, Center for Biofilm Engineering, Montana State University
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38. The Basis of Population Growth: Binary Fission
Parent cell enlarges
Chromosomes are duplicated
Cell envelope pulls together in the center of the cell to form a septum
Cell divides into two daughter cells
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39. The Rate of Population Growth
Generation time or doubling time:
The time required for a complete fission cycle
Each new fission cycle doubles the population
As long as the environment remains favorable, the doubling effect can continue at a constant rate
The length of the generation time is a measure of the growth rate of an organism
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40. The Rate of Population Growth
Exponential growth:
The growth pattern of microbes
Useful to express the populations of microbes as exponents or logarithms
Plotting data from a growing bacterial population:
Number of cells as a function of time
Can be represented logarithmically or arithmetically
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41. Growth Curve in a Bacterial Culture
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42. Stages in the Normal Growth Curve
Lag phase:
Flat period on the graph when the population appears not to be growing
Newly inoculated cells require a period of adjustment, enlargement, and synthesis
Cells are not yet multiplying at their maximum rate
Population of cells is so sparse that the sampling misses them
Exponential growth or log phase:
Period during which the growth curve increases geometrically
Phase will continue as long as cells have adequate nutrients and the environment is favorable

43. Stages in the Normal Growth Curve
Stationary growth phase:
Population enters survival mode
Cells stop growing or grow slowly
Death phase:
Limiting factors intensify and cells begin to die at an exponential rate
Curve dips downward