1. Chapter5 Microbial Nutrition
PA RT II Microbial Nutrition,
Growth, and Control
Chapter5 Microbial Nutrition

2. Outline: Nutrient requirements Nutritional types of microorganisms
5. Microbial Nutrition
Outline:
Nutrient requirements
Nutritional types of microorganisms
Uptake of Nutrients by the Cell
Culture Medium
Isolation of Pure Cultures

3. Concepts
1. Microorganisms require about 10 elements in large quantities, in part because they are used to construct carbohydrates, lipids, proteins, and nucleic acids. Several other elements are needed in very small amounts and are parts of enzymes and cofactors.
2. All microorganisms can be placed in one of a few nutritional categories on the basis of their requirements for carbon, energy, and hydrogen atoms or electrons.
3. Nutrient molecules frequently cannot cross selectively permeable plasma membranes through passive diffusion. They must be transported by one of three major mechanisms involving the use of membrane carrier proteins. Eucaryotic microorganisms also employ endocytosis for nutrient uptake.
4. Culture media are needed to grow microorganisms in the laboratory and to carry out specialized procedures like microbial identification, water and food analysis, and the isolation of articular microorganisms. Many different media are available for these and other purposes.
5. Pure cultures can be obtained through the use of spread plates, streak plates, or pour plates and are required for the careful study of an individual microbial species.

4. Macronutrients
95% or more of cell dry weight is made up of a few major elements: carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, calcium, magnesium and iron.
The first six ( C, H, O, N, P and S) are components of carbonhadrates, lipids, proteins and nucleic acids

5. Trace Elements
Microbes require very small amounts of other mineral elements, such as iron, copper, molybdenum, and zinc; these are referred to as trace elements. Most are essential for activity of certain enzymes, usually as cofactors.

6. Growth Factors
(1)amino acids, (2) purines and pyrimidines, (3) vitamins
Amino acids are needed for protein synthesis,
purines and pyrimidines for nucleic acid synthesis.
Vitamins are small organic molecules that usually make up all or part enzyme cofactors, and only very small amounts are required for growth.

7. Nutritional types of microorganisms
Major nutritional type
Sources of energy,
hydrogen/electrons,
and carbon
Representative microorganisms
Photoautotroph
(Photolithotroph)
Light energy, inorganic hydrogen/electron(H/e-) donor, CO2 carbon source
Algae, Purple and green bacteria, Cyanobacteria
Photoheterotroph
(Photoorganotroph)
Light energy, inorganic H/e- donor,
Organic carbon source
Purple nonsulfur bacteria,
Green sulfur bacteria
Chemoautotroph
(Chemolithotroph)
Chemical energy source (inorganic), Inorganic H/e- donor, CO2 carbon source
Sulfur-oxdizing bacteria, Hydrogen bacteria,
Nitrifying bacteria
Chemoheterotroph
(Chenoorganotroph)
Chemical energy source (organic), Organic H/e- donor, Organic carbon source
Most bacteria, fungi, protozoa

8. CO2 + H2O Light + Chlorophyll （CH2O） +O2
Photoautotroph:
Algae, Cyanobacteria
CO2 + H2O Light + Chlorophyll （CH2O） +O2
Purple and green bacteria
CO2 + 2H2S Light + bacteriochlorophyll （CH2O） + H2O + 2S
Photoheterotroph:
Purple nonsulfur bacteria (Rhodospirillum)
CO2 + 2CH3CHOHCH3 Light + bacteriochlorophyll （CH2O） + H2O + 2CH3COCH3

9. Properties of microbial photosynthetic systems
Property
cyanobacteria
Green and purple bacteria
Purple nonsulfur bacteria
Photo - pigment
Chlorophyll
Bcteriochlorophyll
O2 production
Yes No
Electron donors
H2O
H2, H2S, S
Carbon source
CO2
Organic / CO2
Primary products of energy conversion
ATP + NADPH
ATP

10. Chemoautotroph: H2 O2 H2O NO2- NO3- , H2O NH4+ NO2- , H2O SO4 2-
Bacteria
Electron donor
Electron acceptor
Products
Alcaligens and Pseudomonas sp. H2 O2
H2O
Nitrobacter
NO2-
NO3- , H2O
Nitrosomonas
NH4+
NO2- , H2O
Desulfovibrio
SO4 2-
H2O. H2S
Thiobacillus denitrificans
S0. H2S
NO3-
SO4 2- , N2
Thiobacillus ferrooxidans
Fe2+
Fe3+ , H2O
Nitrifying bacteria
2 NH O NO H2O + 4 H Kcal

11. Culture media
are needed to grow microorganisms in the laboratory and to carry out specialized procedures like microbial identification, water and food analysis, and the isolation of particular microorganisms. A wide variety of media is available for these and other purposes.

12. Pure cultures
can be obtained through the use of spread plates, streak plates, or pour plates and are required for the careful study of an individual microbial species.

13. Uptake of nutrients
Nutrient molecules frequently cannot cross selectively permeable plasma membranes through passive diffusion and must be transported by one of three major mechanisms involving the use of membrane carrier proteins.

14. 1, Phagocytosis – Protozoa
2, Permeability absorption – Most microorganisms
passive transport , simple diffusion
facilitated diffusion
active transport
group translocation

15. passive diffusion
A few substances, such as glycerol, can cross the plasma membrane by passive diffusion. Passive diffusion is the process in which molecules move from a region of higher concentration to one of lower concentration as a result of random thermal agitation.

16. Facilitated diffusion
The rate of diffusion across selectively permeable membranes is greatly increased by the use of carrier proteins, sometimes called permeases, which are embedded in the plasina membrane. Since the diffusion process is aided by a carrier, it is called facilitated diffusion. The rate of facilitated diffusion increases with the concentratioti gradient much more rapidly and at lower concentrations of the diffusing molecule than that of passive diffusion

17. Active transport
Active transport is the transport of solute molecules to higher concentrations, or against a concentration gradient, with the use of metabolic energy input.

18. Group translocation

19. 1, Phagocytosis – Protozoa
2, Permeability absorption – Most microorganisms
passive transport , simple diffusion
facilitated diffusion
active transport
group translocation

20. passive diffusion
A few substances, such as glycerol, can cross the plasma membrane by passive diffusion. Passive diffusion is the process in which molecules move from a region of higher concentration to one of lower concentration as a result of random thermal agitation.

21. Facilitated diffusion
The rate of diffusion across selectively permeable membranes is greatly increased by the use of carrier proteins, sometimes called permeases, which are embedded in the plasina membrane. Since the diffusion process is aided by a carrier, it is called facilitated diffusion. The rate of facilitated diffusion increases with the concentration gradient much more rapidly and at lower concentrations of the diffusing molecule than that of passive diffusion

22. A model of facilitated diffusion
The membrane carrier can change conformation after binding an external molecule and subsequently release the molecule on the cell interior. It then returns to the outward oriented position and is ready to bind another solute molecule.
Because there is no energy input, molecules will continue to enter only as long as their concentration is greater on the outside.

23. Active transport
Active transport is the transport of solute molecules to higher concentrations, or against a concentration gradient, with the use of metabolic energy input.

24. PEP + sugar (outside) pyruvate + sugar-P (inside)
Group translocation
The best-known group translocation system is the phosphoenolpyruvate: sugar phosphotransferase system (PTS), which transports a variety of sugars into procaryotic cells while Simultaneously phosphorylating them using phosphoenolpyruvate (PEP) as the phosphate donor.
PEP + sugar (outside) pyruvate + sugar-P (inside)

25. The phosphoenolpyruvate: sugar phosphotransferase system of E. coli
The phosphoenolpyruvate: sugar phosphotransferase system of E. coli. The following components are involved in the system: phosphoenolpyruvate, PEP; enzyme 1, E I; the low molecular weight heat-stable protein, HPr; enzyme 11, E II,- and enzyme III, E III.

26. Simple comparison of transport systems
Items
Passive diffusion
Facilitated diffusion
Active transport
Group translocation
carrier proteins
Non
Yes
transport speed
Slow
Rapid
against gradient
transport molecules
No specificity
Specificity
metabolic energy
No need
Need
Solutes molecules
Not changed
Changed

27. Mode of action of antibacterial antibiotics

28. Symbiosis of peptidoglycan

29. Questions
1. Throughout history, spices have been used as preservatives and to cover up the smell/taste of food that is slightly spoiled. The success of some spices led to a magical, ritualized use of many of them and possession of spices was often limited to priests or other powerful members of the community. a. Choose a spice and trace its use geographically and historically. What is its common-day use today? b. Spices grow and tend to be used predominantly in warmer climates. Explain.
2. Design an experiment to determine whether an antimicrobial agent is acting as a cidal or static agent. How would you determine whether an agent is suitable for use as an antiseptic rather than as a disinfectant?
3. Suppose that you are testing the effectiveness of disinfectants with the phenol coefficient test and obtained the following results.

30. Outline Chapter 6 Microbial growth The Growth Curve Cell life cycle
Measurement of Microbial Growth
Measurement of Cell Mass
Growth Yields and the Effects of a Limiting Nutrient
The Continuous Culture of Microorganisms
The Chemostat
The Influence of Environmental Factors on Growth

31. Concepts
  Growth is defined as an increase in cellular constituents and may result in an increase in an organism's size, population number, or both.
 When microorganisms are grown in a closed system, population growth remains exponential for only a few generations and then enters a stationary phase due to factors like nutrient limitation and waste accumulation. If a population is cultured in an open system with continual nutrient addition and waste removal, the exponential phase can be maintained for long periods.

32. 3. A wide variety of techniques can be used to study microbial growth by following changes in the total cell number, the population of viable microorganisms, or the cell mass.
4. Water availability, pH, temperature, oxygen concentration, pressure, radiation, and a number of other environmental factors influence microbial growth. Yet many microorganisms, and particularly bacteria, have managed to adapt and flourish under environmental extremes that would destroy most organisms.

33. Growth definition:
Growth may be generally defined as a steady increase in all of the chemical components of an organism. Growth usually results in an increase in the size of a cell and frequently results in cell division

34. S phase in which replication of the genome occurs
Cell life cycle in Eukaryotic cells
G1 Primary growth phase of the cell during which cell enlargement occurs, a gap phase separating cell growth from replication of the genome
S phase in which replication of the genome occurs
G2 Phase in which the cell prepares for separation of the replicated genomes, this phase includes synthesis of microtubules and condensation of DNA to form coherent chromosomes, a gap phase separating chromosome replication from miosis.
M phase called miosis during which the microtubular apparatus is associated and subsequently used to pull apart the sister chromosomes.
Eukaryotic cell:
Prokaryotic cell:
G S G M
G R D

36. Binary fision
Most bacterial cells reproduce asexually by binary fision, a process in which a cell divides to produce two nearly equal-sized progeny cells. Binary fision involves three processes:
Increase in cell size (cell elongation),
DNA replication
Cell division

37. Growth curve of bacteria
Lag Phase
Exponential Phase
 Stationary Phase
Death Phase

38. Growth curve of bacteria
Lag Phase
Exponential Phase
 Stationary Phase
Death Phase

39. Stationary Phase
Logarithmic growth phase
Death Phase
Lag Phase
(a)      Lag phase: cells begin to synthesize inducible enzymes and use stored food reserves.
(b)     Logarithmic growth phase: the rate of multiplication is constant.
(c)      Stationary phase: death rate is equal to rate of increase.
(d) Death phase: cells begin to die at a more rapid rate than that of reproduction.

40. generation time
The time required for a cell to divide (and its population to double) is called the generation time.
Suppose that a bacterial population increases from103 cells to 109 cells in 10 hours. Calculate the generation time.
Nt = No x 2n
G = t log2 / log Nt – log No
No = number of bacteria at beginning of time interval.
Nt = number of bacteria at end of any interval of time (t).
G = generation time
T = time , usually expressed in minutes
n = number of generation
Number of cells
Time

41. fermenter

42. Continuous culture of microorganisms
Chemostat
Chemostat used for continuous cultures. Rate of growth can be controlled either by controlling the rate at which new medium enters the growth chamber or by limiting a required growth factor in the medium.

43. Effect of temperature on bacterial growth rate
Bacteria grow over a range of temperatures; they do not reproduce below the minimum growth temperattire nor above the maximum growth temperature. Within the temperature growth range there is an optimum growth temperature at which bacterial reproduction is fastest.

44. Enzymes exhibit a Q10 so that within a suitable temperature range the rate of enzyme activity doubles for every 10' C rise in temperature.

45. Microorganisms are classified as psychrophiles, mesophiles
Microorganisms are classified as psychrophiles, mesophiles.thermophiles, and extremethemophiles based on their optimal growth temperature.

46. Effect of oxygen concentration – reduction potential
Effect of oxygen concentration on the growth of various bacteria in tubes of solid medium

47. 厌氧菌的培养

48. (a) Obligate aerobes-growth occurs only in the short distance to which the oxygen diffuses into the medium.
(b) Facultative anaerobes growth is best near the surface, where oxygen is available, but occurs throughout the tube.
(c) Obligate anaerobes-oxygen is toxic, and there is no growth near the surface.
(d) Aerotolerant anaerobes-growth occurs evenly throughout the tube but is not better at the surface because the organisms do not use oxygen.
(e) Microaerophiles, aerobic organisms that do not tolerate atmospheric concentrations of oxygen-growth occurs only in a narrow band of optimal oxygen concentration.

49. Effect of pH value on microbial growth
Bacteria: Neutral condition
Fungi: Acidic condition
Actinomycetes: Alkaline condition

50. Water activity aw = P solution / P water
The water activity of a solution is 1/100 the relative humidity of the solution (when expressed as a percent), or it is equivalent to the ratio of the solution's vapor pressure to that of pure water.
aw = P solution / P water
Approximate lower aw limits for microbial growth:
0.90 – 1.00 for most bacteria, most algae and some fungi as Basidiomycetes,Mucor, Rhizopus.
0.75 for Halobacterium, Aspergillus…
0.60 for some saccharomyces species

51. Plasmolysis
If the concentration of solutes, such as sodium chloride, is higher in the surrounding medium (hypertonic), then water tends to leave the cell. The cell membrane shrinks away from the cell wall (an action called plasmolysis), and cell growth is inhibited.
Normal cell
Plasmolyzed cell

52. Control of microbial growth
Definitions:
Sterilization – the process of destroying all forms of microbial life on an object or in a material.
Disinfection – the process of destroying vegetative pathogens but not necessary endospores.
Antisepsis – chemical disinfection of skin, mucous membranes or other living tissues