1. Monera
e.g. Bacteria

2. Learning Objectives Name 3 types of bacterial cell
Explain reproduction of bacteria
Explain nutrition of bacteria
State the factors affecting growth of micro-organisms
Define the term pathogenic
Define the term antibiotics
State the role of antibiotics
Outline the potential abuse of antibiotics
Name 2 Beneficial & 2 Harmful bacteria

3. Bacteria in pond water

4. Bacteria on apple

5. Bacteria
Bacteria belong to the kingdom Monera. They are unicellular organisms
Also known as prokaryotes as they have no membrane bound nucleus or membrane bound cell organelles
They are classified according to three shapes
Spherical (cocci)
Rod (bacillus)
Spiral (spirillum)

6. Bacterial Shapes

7. Spherical (cocci)
E.g. Staphylococcus aureus
Causes pneumonia

8. Rod (bacillus) E.g. Bacillus anthracis Cause of anthrax
Escherichia coli (E.coli)
Live in human gut

9. Spirillum (spiral)
E.g.Treponema pallidum
Causes syphilis

10. Bacterial size

11. Bacterial Structure

12. Bacterial Structure Cell wall flagella cytoplasm plasmid Cell membrane
Strand of DNA
capsule

13. Cell Parts & Function Cell wall - shape & structure
Cytoplasm - contains ribosomes and storage granules but no mitochondria or chloroplasts
Nuclear material -single chromosome of DNA
Capsule* - protection
Flagella* - movement
Plasmid* -circular piece of DNA containing few genes for drug resistance
* Sometimes present.
*Sometimes present

15. Bacterial Reproduction

16. Bacterial reproduction
Bacteria reproduce asexually
The method used by a bacteria to reproduce is called Binary Fission

17. Binary Fission
The chromosome attaches to the plasma membrane and the DNA is replicated
Cell wall
Cytoplasm
Plasma membrane
Chromosome

18. The cell elongates and the two chromosomes separate
Binary Fission
The cell elongates and the two chromosomes separate

19. The cell wall grows to divide the cell in two
Binary Fission
The cell wall grows to divide the cell in two

20. Two identical daughter cells are formed
Binary Fission
Two identical daughter cells are formed

22. Bacterial Reproduction
Bacteria reproduce asexually - their offspring are genetically identical
As there is little recombination of genetic material in this method of reproduction one would expect that bacteria would be slow to evolve
Bacteria has a very short lifecycle (some can reproduce every 20 minutes).
New mutations can spread very quickly
This is how bacteria evolve resistance to new antibiotics

23. Endospore formation
Some bacteria can withstand unfavourable conditions by producing endospores

24. These are formed when the bacterial chromosome replicates
Endospore formation
These are formed when the bacterial chromosome replicates

25. Endospore formation
One of the new strands becomes enclosed in a tough-walled capsule called an endospore
The parent cell then breaks down and the endospore remains dormant
Endospore

26. Endospore formation
When conditions are favourable the spores absorb water, break their walls and reproduce by binary fission

27. Bacterial Nutrition

28. Autotrophic and Heterotrophic
Autotrophic – organisms which make their own food
Heterotrophic – organisms which take in food made by other organisms

29. Autotrophic Bacteria Photosynthetic bacteria
Use light energy to make food
E.g. purple sulphur bacteria

30. Autotrophic Bacteria Chemosynthetic bacteria
Use energy from chemical reactions to make food
E.g. Nitrifying bacteria that convert ammonia to nitrates in the nitrogen cycle

31. Heterotrophic Bacteria
Saprophytic Bacteria
Live off dead organic matter
E.g. bacteria of decay in the soil

32. Heterotrophic Bacteria
Parasitic Bacteria
Take food from live host
Some cause diseases
E.g. Bacillus anthracis
causes anthrax

33. Bacterial Nutrition

34. Factors affecting the growth of bacteria
For the maximum growth rate bacteria must have access to a food source and the conditions of their environment must be monitored closely

35. Too much or too little of any of the following factors will slow down the growth of bacteria:
Temperature
Oxygen concentration pH
External solute concentration
Pressure

36. Temperature Most bacteria grow well between 20°C and 30°C.
Some can tolerate much higher temperatures without their enzymes becoming denatured.
Low temperatures slow down the rate of reaction of enzymes resulting in slower growth

38. pH
If a bacterium is placed in an unsuitable pH its enzymes will become denatured

41. Oxygen concentration
Aerobic bacteria require oxygen for respiration e.g. Streptococcus
This is why oxygen is sometimes bubbled through bioreactors

42. Anaerobic bacteria do not require oxygen to respire
Facultative anaerobes can respire with or without oxygen e.g. E.Coli (found in intestines)
Obligate anaerobes can only respire in the absence of oxygen e.g. Clostridium tetani (causes tetanus)

43. External Solute concentration
Bacteria can gain or lose water by osmosis
If the external solute concentration is
higher than the bacterial cytoplasm water will move out of the bacteria (Dehydration)
Food preservation techniques are based on this

45. Pressure The growth of most bacteria is inhibited by high pressures.
Some bacteria can withstand high pressures. Pressure tolerant bacteria for use in bioreactors can be formed by genetic engineering techniques.

46. Growth curve for bacteria

47. When a fresh medium is innoculated with a given number of cells and the population growth is monitored over a period of time, plotting the data will yield a typical bacterial growth curve Note: viable bacteria = living bacteria
Stationary
Numbers of Viable Bacteria
Death/Decline
Log
Survival
Lag
Time

48. The Five Stages of Bacterial Growth
Lag Phase
An adjustment period where the bacteria adapt to the new environmental conditions (pH, nutrients, temperature.). There is no significant increase in numbers with time.
Log/Exponential Phase
Rapid growth of bacteria, they start multiplying exponentially at an accelerated pace doubling in number every few minutes. Conditions are optimal for growth.

49. Stationary Phase
Equal rate of growth and death so that overall bacterial numbers stay the same. At this point bacteria are competing for food, space, moisture and oxygen. There is also a build up of wastes.
4.Death Phase
Rapid cell death usually due to the cells bursting open. This is due to a lack of nutrients, increased competition and a toxic environment.
5.Survival Phase
A small number survive as endospores.

50. Beneficial and harmful bacteria
Lactobacillus converts milk to yoghurt and cheese
Antibiotics can be formed by some microorganisms
Bacteria in the colon help produce vitamins
G.M.O.’s are used to make insulin, enzymes, drugs, vits.
Bacteria are active in the Carbon and Nitrogen Cycles
HARMFUL
Pathogenic Bacteria can cause diseases in humans and animals.
Pathogenic Bacteria can cause diseases in plants.
Bacteria can cause food spoilage
Bacteria can cause tooth decay.

51. Economic importance of bacteria
Beneficial bacteria
Bacteria such as Lactobacillus are used to convert milk to products such as cheese and yoghurt
Genetically modified bacteria e.g. E. Coli are used to make products such as insulin, enzymes, drugs, food flavourings and vitamins

52. Economic importance of bacteria
Harmful bacteria
Micro-organisms that cause disease are called pathogens
E.g. Bacillus anthracis causes anthrax in humans
If they enter the body through a wound they can multiply and effect the nerves and activity of muscles
Other bacterial diseases include tuberculosis, typhoid, cholera, diphtheria and brucellosis

53. TB

54. Scarlet fever

55. Bacterial meningitis

56. Antibiotics

57. Antibiotics
Antibiotics are substances produced by micro-organisms that stop the growth of, or kill, other micro-organisms without damaging human tissue

58. Antibiotics
Antibiotics can be used to control bacterial and fungal infections but do not effect viruses

59. Antibiotics
The first antibiotic Penicillin isolated from a fungus by Sir Alexander Fleming
Now antibiotics are mostly produced by genetically engineered bacteria

60. Examples:
Streptomycin
Neomycin
Tetracycline

61. Antibiotics
When an antibiotic is used to treat an infection most of the bacteria are killed
Mutations in bacterial genes can allow bacteria to develop antibiotic resistance.
Antibiotics will then kill ‘sensitive’ bacteria and favour resistant bacteria.
Bacterial strains have emerged which are resistant to almost all known antibiotics (multi-resistant). As a result present day antibiotics become ineffective. MRSA is one example.

62. Bacteria gain resistance to antibiotics by:
Mutation
Gaining the resistant gene from plasmids

64. Abuse of antibiotics:
Poor prescribing methods – eg for viral infections
Poor patient practice – patients often dont finish the course of antibiotics thus increasing the chance of resistant strains developing.
Agriculture – antibiotics are used in growth promotion, disease prevention + treatment. This has led to resistant strains and allergic reactions in consumers.

65. Batch and Continuous Flow
food processing

66. A bioreactor is a large stainless vessel in which bioprocessing takes place

67. Food processing
Modern bio-processing methods involve the use of bacteria (and other organisms) to produce a wide range of products.
These include dairy products e.g. yoghurts and cheeses, artificial sweeteners, flavourings, vitamins and alcohol products such as wines and beers.

68. There are two main methods of food processing:
Batch food processing
Continuous flow food processing

69. Batch food processing
In batch food processing a fixed amount of sterile nutrient is added to the micro-organisms in the bioreactor.
The micro-organisms go through all the stages of a typical growth curve
i.e. The Lag, Log, Stationary and Death stages
Although the reaction may be stopped before the death stage as very little product will be formed at this stage.

70. In Batch Processing most of the product is formed during the stages highlighted below
Lag phase
Death Phase
Log Phase
Stationary Phase
Number of Bacteria
Time (days)

71. At the end of production the bioreactor is cleared out
At the end of production the bioreactor is cleared out. The product is separated from the rest of the solution and is purified.
The bioreactor is cleaned and re-sterilised.
The process can then be repeated.

72. Bioreactor for Batch Food Processing
Fixed amount of Nutrients and micro-organisms added here
Gas out here
Stirrer
Product is released at the end of the process
Sparger
Oxygen (if required) in here

73. Advantages
Uses
To make antibiotics
Used when a small amount of product is needed
Product required can be changed easily
Easy to control
Cheap to run

74. Continuous flow food processing
In continuous flow food processing nutrients are continuously fed into the bioreactor.
At the same time the culture medium product (containing some micro-organisms) is continually withdrawn.
In this method of food processing micro-organisms are maintained in the Log phase of growth and the process can continue uninterrupted for weeks, even months.

75. In continuous flow bioreactors factors such as temperature, pH, rate of stirring, concentration of nutrients, oxygen and waste products are constantly monitored in order to maintain growth in the Log phase and therefore produce the maximum yield.

76. In Continuous Flow Processing most of the product is formed during the stage highlighted below
Log Phase
Lag phase
Number of Bacteria
Time (months)

77. Bioreactor for Continuous Flow Food Processing
Nutrients fed in
continuously
Gas out here
Product (and culture medium) flows out continuously
Stirrer
Sparger
Oxygen
in here
Product

78. Use: To make single cell protein
Advantages
Disadvantages
High product yield as microbes are kept in log phase.
Quicker as no need to empty and clean.
Easier to extract product.
Only suits a product that is made during the log phase.
Requires high tech monitoring and highly trained staff.

79. Continuous flow processing
Learning check…
Using the diagrams below outline the differences between batch and continuous flow food processing
Batch processing
Continuous flow processing

80. Syllabus

81. Depth of treatment
Bacterial cells: basic structure (including plasmid DNA), three main types. Reproduction. Nutrition.
Factors affecting growth
Understanding of the term “pathogenic”
Definition and role of “antibiotics”

82. Contemporary issues and technology
Economic importance of bacteria: examples of any two beneficial and any two harmful bacteria.
Potential abuse of antibiotics in medicine.