This document discusses microbial nutrition and growth. It explains that microbes require nutrients for energy, cellular activities, and constructing new cellular components. The main nutrients include carbon, nitrogen, phosphorus, and trace elements. It categorizes microbes based on their carbon and energy sources. It also describes the physical and chemical requirements for microbial growth, including temperature, pH, oxygen levels, and nutrients. It discusses culture media, methods for measuring growth, and techniques for obtaining pure cultures.

1. MICROBIAL NUTRITION AND
GROWTH
BY
DR JAWAD NAZIR
ASSISTANT PROFESSOR
DEPARTMENT OF MICROBIOLOGY
UNIVERSITY OF VETERINARY AND ANIMAL SCIENCES, LAHORE

2. Microbial nutrition and growth
Requirement of Nutrition?
 To obtain energy
 To carry out normal cellular activities
 Construct new cellular components

3. Microbial nutrition and growth
Common Nutrients
Macronutrients :
 95 % of cell dry mass is made up of
 Carbon, oxygen, hydrogen, nitrogen, sulpher, phosphorus
 Components of organic molecules
 Potassium: required by enzymes (protein synthesis)
 Calcium: component of spore
 Magnesium : cofactor for enzymes
 Iron: cytochrom and electron transport chain

4. Microbial nutrition and growth
Common Nutrients
Trace elements (Micronutrients):
 Normally serve as co factor in enzymes
 Manganese, Zinc, Cobalt, Molybdenum, nickel, and copper
 Required in such small amount that contaminants in
water, glassware or media ingredients are adequate to
fulfill their requirements
Nutrients required per litre of medium:
 Major ingredients required in grams
 Minor ingredients required in mili grams
 Trace elements required in micrograms

5. Microbial nutrition and growth
Categorization of bacteria
Carbon:
 Autotroph
 Heterotroph
Energy source:
 Phototroph
 Chemotroph
Hydrogen or electron source:
 Lithotroph
 Organotrophs

6. Microbial nutrition and growth
Nutritional types of microorganisms
Photoautotrophs:
 Who use light as energy source and CO2 as carbon source
 Oxygenic in nature
 Algae, blue green bacteria, purple and green sulfur
bacteria
Photoheterotrophs:
 Who use light as energy source and an organic carbon
source
 Common inhabitant of polluted lakes and streams
 Purple non sulfur bacteria and green non sulfur bacteria

7. Microbial nutrition and growth
Nutritional types of microorganisms
Chemoautotroph:
 Who use inorganic chemicals as energy source and
CO2 as carbon source
 Nitrosomonas, Nitrobacter, Hydrogenomonas,
Thiobacillus ferrooxidans
Chemohetrotroph:
 Who use organic molecules as a source of carbon and
energy
 Same organic molecule satisfy all the requirements
 All pathogenic bacteria fall in this category

8. There is no naturally occuring organic
molecule that cannot be utilized by
some microorganisms

9. Nutritional classification of Microorganisms

10. Microbial nutrition and growth
Growth factors
Organic molecules required for cell structure and
function and can not be synthesized by a specific
microbe is called as growth factor
 Amino acids
 Nucleotides (purine pyrimidine)
 Vitamins

11. Microbial nutrition and growth
Microbial growth?
 Microbial growth = increase in number of cells
 Not cell size

12. Microbial nutrition and growth
Requirements of growth
Physical requirements:
 Temperature
 pH
 Osmotic pressure
Chemical requirements:
 Carbon, nitrogen, sulfr, phosphorus
 Trace elements
 Oxygen
 Organic growth factors

13. Microbial nutrition and growth
Physical Requirements
Temperature:
 Minimum growth temperature
 Optimum growth temperature
 Maximum growth temperature

14. Temperature

15. Food spoilage temperatures

16. Effect of temperature on food spoilage

17. Microbial nutrition and growth
 pH:
 Most bacteria grow between pH 6.5 and 7.5
 Molds and yeasts grow between pH 5 and 6
 Acidophiles grow in acidic environments
Physical Requirements

18. Microbial nutrition and growth
Classes of microbes based upon pH

19. Microbial nutrition and growth
pH and microbial growth

20. pH range of various products

21. Microbial nutrition and growth
Physical Requirements
Osmotic pressure:
 Hypertonic environments, increase salt or sugar,
cause plasmolysis
 Extreme or obligate halophiles require high
osmotic pressure
 Facultative halophiles tolerate high osmotic
pressure

22. Plasmolysis (shrinkage)

23. Microbial nutrition and growth
Chemical requirements
Carbon:
 Structural organic molecules, energy source
 Chemoheterotrophs use organic carbon sources
 Autotrophs use CO2

24. Microbial nutrition and growth
Chemical requirements
Nitrogen:
 In amino acids, proteins
 Most bacteria decompose proteins
 Some bacteria use ammonium (NH4
+) or Nitrate (NO3
)
 A few bacteria use N2 in nitrogen fixation
Sulfur:
 In amino acids, thiamine, biotin
 Most bacteria decompose proteins
 Some bacteria use sulfate (SO4
2) or H2S
Phosphorus:
 In DNA, RNA, ATP, and membranes
 Phosphate (PO4
3)is a source of phosphorus

25. Microbial nutrition and growth
Chemical requirements
Trace elements:
 Inorganic elements required in small amounts
 Usually as enzyme cofactors

26. Microbial nutrition and growth
Oxygen (O2)
The Requirements for Growth: Chemical Requirements
obligate
aerobes
Faultative
anaerobes
Obligate
anaerobes
Aerotolerant
anaerobes
Microaerophiles

27. Microbial nutrition and growth
 Singlet oxygen: O2 boosted to a higher-energy state
 Superoxide free radicals: O2

2
 Peroxide anion: O2
2
 Hydroxyl radical (OH)
Toxic Forms of Oxygen

28. Microbial nutrition and growth
 Organic Growth Factors
 Organic compounds obtained from the environment
 Vitamins, amino acids, purines, pyrimidines
The Requirements for Growth: Chemical Requirements

29. Microbial nutrition and growth
 Culture Medium: Nutrients prepared for microbial
growth
 Sterile: No living microbes
 Inoculum: Introduction of microbes into medium
 Culture: Microbes growing in/on culture medium
Culture Media

30. Microbial nutrition and growth
Types of media
 Broth
Liquid medium
 Agar
Solid medium

31. Microbial nutrition and growth
 Complex polysaccharide
 Used as solidifying agent for culture media in Petri
plates, slants, and deeps
 Generally not metabolized by microbes
 Liquefies at 100°C
 Solidifies ~40°C
Agar

32. Microbial nutrition and growth
 Chemically Defined Media: Exact chemical
composition is known
 Complex Media: Extracts and digests of yeasts,
meat, or plants
 Nutrient broth
 Nutrient agar
Culture Media

33. Microbial nutrition and growth
Culture Media
Table 6.2 & 6.4

34. Microbial nutrition and growth
Selective media
 Suppress unwanted microbes and encourage
desired microbes.
 MacConkey agar:
 Bile salts allow intestinal bcteria
 Staph-110 media:
 High salts concentration make selective for staph.
 Campylobacter selective media:
 Polymyxin B, Trimethoprim, Rifamycin

35. Microbial nutrition and growth
 Make it easy to distinguish colonies of different microbes.
Differential Media
Lactose fermenter and non-fermenter on MacConkey agar

36. Microbial nutrition and growth
Differential Media
Salmonella Shigella agar

37. Microbial nutrition and growth
Enriched medium
 Used to grow fastidious bacteria
 Substances like blood, serum, egg are added to the
basal medium.
 Blood agar, Chocolate agar, PPLO agar

38. Microbial nutrition and growth
 Encourages growth of desired microbe
 Selenite broth used to enhance the growth of
Salmonella species as sodium selenite is toxic for
E.coli and Proteus
 Inoculate fecal material in selenite broth
 Incubate for 18-24 hours
 Culture on selective or enriched media
Enrichment Media

39. Microbial nutrition and growth
 Reducing media
 Contain chemicals (thioglycollate or oxyrase) that
combine O2
 Heated to drive off O2
Anaerobic Culture Methods

40.  Anaerobic
jar
Anaerobic Culture Methods

41.  Anaerobic
chamber
Anaerobic Culture Methods

42.  Candle jar
 CO2-packet
Capnophiles require high CO2

43. Microbial nutrition and growth
Purifying a culture
 A pure culture contains only one species or strain
 A colony is a population of cells arising from a
single cell or spore or from a group of attached
cells
 A colony is often called a colony-forming unit (CFU)

44. Microbial nutrition and growth
Streak Plate

45. Microbial nutrition and growth
Streak Plate

46. 46
Growth of Staphylococcus aureus on Manitol Salt Agar
results in a color change in the media from pink to yellow.

47. Microbial nutrition and growth 47
Laboratory Culture of Microorganisms
 Microorganisms can be grown in the
laboratory in culture media containing the
nutrients they require.
 Successful cultivation and maintenance of
pure cultures of microorganisms can be
done only if aseptic technique is practiced to
prevent contamination by other
microorganisms.

48. Microbial nutrition and growth 48
Microbial growth
 Microbes grow via binary fission, resulting in exponential
increases in numbers
 The number of cell arising from a single cell is 2n after n
generations
 Generation time is the time it takes for a single cell to grow
and divide

49. 49
Binary Fission

50. 50
Rapid Growth of Bacterial Population

51. Microbial nutrition and growth 51
Growth curve
 During lag phase, cells are recovering from a period of no
growth and are making macromolecules in preparation for
growth
 During log phase cultures are growing maximally
 Stationary phase occurs when nutrients are depleted and
wastes accumulate (Growth rate = death rate)
 During death phase death rate is greater than growth rate

52. Microbial nutrition and growth 52
Methods used to measure microbial growth
 Count colonies on plate or filter (counts live
cells)
 Microscopic counts
 Flow cytometry (FACS)
 Turbitity

53. Microbial nutrition and growth 53
Viable counts
 Each colony on plate or filter arises from single live cell
 Only counting live cells

54. 54
Direct Count
Pour Plate

55. 55

56. 56
Direct Count
Spread or
Streak Plate

57. Microbial nutrition and growth 57

58. Microbial nutrition and growth 58
Microscopic counts
 Need a microscope, special slides, high power
objective lens
 Typically only counting total microbe numbers, but
differential counts can also be done

59. Microbial nutrition and growth 59
Turbitity
 Cells act like large particles
that scatter visible light
 A spectrophotometer sends a
beam of visible light through
a culture and measures how
much light is scattered
 Scales read in either
absorbance or %
transmission
 Measures both live and dead
cells

60. Microbial nutrition and growth 60
Inoculation
 Sample is placed on sterile medium providing
microbes with the appropriate nutrients to sustain
growth.
 Selection of the proper medium and sterility of all
tools and media is important.
 Some microbes may require a live organism or living
tissue as the inoculation medium.

61. Microbial nutrition and growth 61
Incubation
 An incubator can be used to adjust the proper growth
conditions of a sample.
 Need to adjust for optimum temperature and gas
content.
 Incubation produces a culture – the visible growth of
the microbe on or in the media

62. Microbial nutrition and growth 62
Isolation
 The end result of inoculation and incubation is isolation.
 On solid media we may see separate colonies, and in
broth growth may be indicated by turbidity.
 Sub-culturing for further isolation may be required.

63. Microbial nutrition and growth 63
Inspection
 Macroscopically observe cultures to note color,
texture, size of colonies, etc.
 Microscopically observe stained slides of the culture
to assess cell shape, size, and motility.

64. Microbial nutrition and growth 64
Identification
 Utilize biochemical tests to differentiate the microbe
from similar species and to determine metabolic
activities specific to the microbe.

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