Chpt. 21 Monera

1. Chpt. 21 Monera

2. Monera • Bacteria belong to the kingdom monera. • Bacteria are present in a wide range of habitats • including both land and water environments e.g. salt • water, soil, plants, animals etc. • Bacteria also survive in extreme environments e.g. hot • springs, swamps, human intestines, human stomach • (pH 2) etc. • Bacteria are prokaryotes i.e. no nucleus or membrane • enclosed organelles – mitochondria. • Bacteria are unicellular – single celled. • Bacteria contain DNA plasmids.

3. Bacterial Size

4. Bacterial Structure

5. Bacterial Structure Food Reserve Cell wall Cell membrane Ribosome Flagella DNA (Chromosome) Cytoplasm Capsule Plasmid

6. General Structure of Bacterium Cell Wall: - made of sugars and protein - prevents bacteria from swelling with water and bursting Cell Membrane: often has infoldings called mesosomes which: a) carry out respiration b) help during cell division Capsule: - sometimes present - takes form of a semi-solid capsule or a more liquid slime layer.

7. General Structure of a Bacterium Chromosome: - one chromosome - consists of a strand of DNA - no surrounding membrane - does not contain protein Plasmids: - sometimes present - small DNA loops - contain genes that are responsible for bacterial resistance to antibiotics Cytoplasm: - contain ribosome's and numerous storage granules (food or waste) Flagellum: - sometimes present - flagella allows bacteria to move by themselves i.e. they are motile.

8. General Structure for a Bacterium

9. Bacterial Types • Bacteria are classified according to three shapes: • Spherical (Cocci) • Rod (Bacillus) • Spiral (Spirrillum)

10. Bacterial Types

11. Bacterial Types • Spherical (Cocci): • Round bacteria which can be found in pairs, chains or • clusters. • -E.g. Staphoolococcus aureus • causes pneumonia

12. Bacterial Types Rods (Bacillus): - E.g. Bacillus anthracis Cause of anthrax - Escherichia coli (E.coli) Live in human gut

13. Bacterial Types Spiral (Spirillum): - E.g. Treponema pallidum Causes syphilis - E.g. Cholera

14. Reproduction in Bacteria • Bacteria reproduce asexually • The method used by a bacteria to reproduce is called • Binary Fission.

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

16. Binary Fission • The cell elongates and the two chromosomes separate

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

18. Binary Fission • Two identical daughter cells are formed

19. Binary Fission

20. Mutations in Bacteria • 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. • New mutations can spread very quickly within rapidly growing bacteria allowing them to evolve very fast. • This is how bacteria evolve resistance to new antibiotics.

21. Endospores • Some bacteria can withstand unfavourable conditions • by producing endospores.

22. Endospore Formation • These are formed when the bacterial chromosome • replicates.

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

24. Endospore Formation • When conditions are favourable the spores absorb • water, break their walls and reproduce by binary • fission. • Note: endospores are very difficult to kill – can • withstand lack of food and water, high temperatures • and most poisons.

25. Bacterial Nutrition • Bacteria obtain food in four different ways which can • be grouped under two headings: • Autotrophic Heterotrophic Photosynthetic Chemosynthetic Saprophytes Parasites

26. Autotrophic Organisms: are organisms which can make their own food. Photosynthetic bacteria: • Source of energy = light • Chlorophyll on membranes within the cell. • Some bacteria have different pigments than plants – • use mostly red light. • Some bacteria live on hydrogen sulphide gas instead of • water – purple sulphur bacteria.

27. Autotrophic Bacteria • Chemosynthetic Bacteria: • make their own food using energy from reactions • involving ammonia, sulphur and iron compounds. • E.g. Nitrifying bacteria that convert ammonia • to nitrates in the nitrogen cycle

28. Heterotrophic Organisms: organisms which take in food made by other organisms. • Saprophytes: • take in food from dead organic matter e.g. bacteria of • decay in the soil. • some use petrol and oil products as a food source – • clean up oil spills.

29. Heterotrophic Bacteria • Parasites: • take in food from a live host resulting in damage to • host. • Examples of disease causing bacteria include: • cholera • pneumonia

31. Factors Affecting Growth Growth of bacteria is affected by five factors. • Too much or too little of any of these five factors will slow down the growth of bacteria: • Temperature • Oxygen concentration • pH • External solute concentration • Pressure

32. 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 bacterial • growth. • High temperature bacteria used in biotechnology • resulting in a) faster bacterial metabolism • b) higher rate of product formation

33. Oxygen Concentration • Aerobic bacteria: require oxygen for respiration e.g. • Streptococcus. • Anaerobic bacteria: do not require oxygen to respire • e.g. Clostridium. • 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)

34. pH • Bacterial enzymes work at specific pH values, outside • this pH value they become denatured. • For most bacteria the most suitable pH is pH7. • Some bacteria can survive at very low or high pH • values.

35. External Solute Bacteria can gain or loose water by a process called osmosis. Case 1: If environment outside a bacterial cell has a higher solute concentration than the bacterial cytoplasm, water will move out of the bacteria (osmosis). As a result bacterium becomes dehydrated preventing further growth or reproduction. Case 2: If environment outside a bacterial cell has a lower solute concentration than the bacterial cytoplasm, water will enter the bacteria (osmosis). - cell wall prevents bacterium from bursting - most bacteria live in these conditions.

36. Pressure • High pressure damages bacterial cell walls. • Some bacteria can withstand very high pressures – • bacteria in deep-sea vents. • Genetically modified bacteria are used to allow • bacteria to survive in bioreactors that require high • pressure.

37. Economic Importance of Bacteria ( Must know 2 beneficial and 2 disadvantages 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

38. 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. • Bacteria cause food decay: • E.g. Lactobacilli cause milk to turn sour

39. Beneficial and harmful bacteria 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. BENEFICIAL • 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 and other useful • compounds • Bacteria are active in the • Carbon and Nitrogen Cycles

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

41. Antibiotics Antibiotics can be used to control bacterial and fungal infections but do not effect viruses E.g. Penicillin, streptomycin

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

43. Antibiotic Resistance • When an antibiotic is used to treat an infection most of • the bacteria are killed. • However 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.

45. Potential Abuse of Antibiotics Overuse of antibiotics: • This results in the increased growth of antibiotic • resistant bacteria. • Failure of some patients to complete a course of • antibiotics prescribed to them by a doctor allows the • bacteria to survive and re-grow.

46. Growth Curves of Monera Higher Level Binary Fission in monera can occur every 20 minutes resulting in a very fast increase in bacterial numbers. Because of this we use a special scale called the logarithmic scale to represent these large numbers. In a logarithmic scale each division represents a unit increase in the value of x in the term 10x. 100 = 0 101 = 10 102 = 100 103 = 1000 104 = 10,000 105 = 100,000 etc

47. Growth Curve for Bacteria This scale allows huge numbers of bacteria to be represented on a graph as shown below: Lag phase Log Phase Stationary Phase Decline Phase Number of Bacteria Logarithmic Scale Time

48. The Lag Phase: • During this phase the bacteria are adapting themselves to their new environment. • Bacteria are producing the enzymes necessary to digest the nutrients on which they are to grow. • The rate of growth begins to increase towards the end of this phase.

49. The Log (Exponential) Phase: • There is a rapid period of growth during this phase due to the fact that: • The rate of cell division is currently at its maximum with the number of bacteria doubling as often as every 20 minutes. • Bacteria have developed the necessary enzymes and there are plenty of nutrients. • Ideal conditions are present i.e. plenty of food, moisture, oxygen etc.

50. The Stationary Phase: • The rate of growth levels off during this period. This is because: • During this period there is a lack of space, moisture, oxygen etc. • The nutrients are becoming used up. • The amount of waste produced by the bacteria themselves is increasing. • The rate at which new cells are produced is equal to the rate at which other cells are dying.