Download Integrated Programme Sec 2 SBGE, LSS Biology Module Topic

Integrated Programme
Sec 2 SBGE, LSS Biology Module
Topic: Micro-organisms and Biotechnology
A.
Characteristics of viruses, bacteria and fungi
B.
Examples of disease causing agents
C.
Role of Micro-organisms in
a. Bread and Alcohol making (yeast)
b. Yoghurt and cheese production (bacteria)
c. Penicillin
D. Genetic Engineering and Bacteria
Characteristics of Viruses
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DNA core
Protein coat (Capsid)
Do not display some characteristics of life
 Feeding
 Respiration
 Growth
 Excretion
Reproduce only within another living cell
Lack of usual cell structure
 Nucleus
 Cytoplasm
 Cell membrane
 Organelles
Replication of Viruses
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Virus particle attaches to host cell membrane
Virus injects DNA/RNA into host cell or whole virus particle enters cell
Virus that enters host cell entirely has its protein coat digested away
Virus then hijacked host cell machinery e.g. ribosomes, enzymes etc to make
new viral DNA/RNA and new protein coat
Assembly of DNA/RNA and protein coat to make new viral particles
New viral particles released through breaking down of host cell
Some viruses have the DNA integrated into host DNA (no symptoms detected in
host yet)
Replication of viruses give rise to signs and symptoms of disease in host
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Viruses and Diseases
Human Immunodeficiency Virus (HIV)
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Spherical
Viral envelope (fatty material)
Glycoprotein – spikes on surface of virus
retrovirus
2 identical RNA strands
reverse transcriptase enzyme convert
RNA to DNA during virus replication
(multiplication of virus particles)
Hepatitis B
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spherical
viral envelope
no spikes
DNA
Influenza
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envelope is derived from plasma membrane
of host cell
spikes
coiled RNA
protein coat (capsid)
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T – series Bacteriophage
infects bacterial cells
 e.g. E.Coli
head made of capsid coat
nucleic acid within coat
tail – where nucleic acid passes to get injected into host
cells
DNA
Viruses and Biotechnology
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Viruses can be used to carry recombined DNA segments in genetic engineering
Bacteria
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Prokaryotic
Visible under light microscope
Can move short distances on their own
Multiply at rapid rates
 20 mins for E. coli
Can be found in various environments
 Hot springs
 Soil
 Oceans etc
0.1 to 10 m in length; 1 m in diameter
Shape – spherical, rod, or spiral
Some have flagella for movement
Some stick together forming characteristic patterns, forming chains or clusters
(allows for classification)
Single stranded coiled up DNA (nucleoid; not bound by nucleus)
Cell wall
 Gram-positive bacteria – thick wall of peptidoglycan (carbohydrate and
protein)
 Retain purple colour of crystal violet stain
 Gram-negative bacteria – 2 layers
 Thinner wall of peptidoglycan and outer wall of carbohydrates, proteins
and lipids
 Does not retain purple colour of crystal violet stain
Ribosomes present
Nutrient storage – inclusions/granules
 Glycogen
 Lipids
 Proteins
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Bacteria Shapes and Forms and Cell Arrangements
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Bacterial Physiology
Nutrition
Photosynthetic – cyanobacteria
 Contains chlorophyll to make food
o Obtain energy from food
 Saprotrophic
 Feed on dead, decaying organisms
 Secrete enzyme to digest organisms externally
 Absorb and assimilate products of digestion
 E.g. Pseudomonas sp.
 Parasitic
 Lives within host cell (of another living organism)
 Known as pathogens
 Usually cause diseases, affecting host
 E.g. Treponema sp. causes syphilis
 Sexually transmitted disease
 Sores on anus, genitals, lips and mouth
 Can cause , paralysis, numbness, gradual
 blindness, and dementia and even DEATH
 Chemoautotrophic
 Makes use of chemical reactions for energy
 E.g.Nitrosomonas sp. makes use of nitrates
 Mutualistic
 Live in host and contribute to health of host
 E.g. Escherichia coli in gut manufactures Vitamin B and K
Respiration
o Aerobic bacteria needs oxygen for respiration to release energy
o Anaerobic bacteria does not need oxygen for respiration to release energy
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Reproduction
o Binary fission (asexual reproduction)
o Divide into 2
 Daughter cell is new bacterium
 Can be very short life cycle
 Each cell takes as short as 20 minutes for some bacteria
 Forming a large colony
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Population Growth
Lag Phase : point of initial inoculation
slow growth because bacteria is adapting to
produce the neccesary enzymens needed
to utilise the nutrients
Exponential Phase:
High nutrients, low waste
products, high cell
division rate.
Stationary phase: nutrients
are used up, high wastes, so
slow growth, more dying
Lag phase
 Bacteria adapting to new environment
Synthesis of new materials
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o Log Phase (Logarithmic)
 Growth is very fast – at maximum rate
 Sufficient nutrient and space
o Stationery phase
 Growth decreases
 Limited resources
 Accumulated waste products
 Bacterial cell death increases
o Declining phase
 Bacteria cell death > growth
 Overcrowding and depletion of resources
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Death Phase: No new cells
produced due to lack of
nutrients and poisoning by
own waste
Uses of Bacteria in Biotechnology
o Can be used to make drugs
o Fermentation
 Brewing, baking, making cheese etc
Fungi
o Unicellular: yeast cells
o Multicellular: mushrooms, toadstools etc.
o Saprophytic
o Live in warm, wet environments
o Threads – hyphae – means of growing (into network – mycelium)
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Types of Fungi
Cap fungi
 Mushrooms
 Toadstool
Filamentous
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Bread mould
Penicillium
Bracket Fungus
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Jew’s Ear
Lingzhi
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Fungi Physiology
Nutrition
o Most are saprophytic

feed on dead organic matter
o Some are parasitic
 Ringworm that feeds on human skin (including the scalp and also between
toes – athlete’s foot)
 Causes a bald patch of scaly skin
 Ring shape rash
 Red and itchy
 Dry and scaly or wet and crusty rash
Reproduction
o Through spores
Yeast
o Special group of fungus
o Thin wall
o Cytoplasm with nucleus and vacuole
o Reproduce by budding
o Rapid budding can result in many small groups of cells attached (where
daughter cells have yet to be separated
o Respire both aerobically and anaerobically; adjust according to presence of
oxygen
 Anaerobic respiration can result in formation of carbon dioxide and alcohol
(fermentation)
 Used in industrial processes
 Beer brewing
 Wine
 Bread making
Penicillium sp.
o For production of anitibiotic penicillin
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Microbes and Man
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Bacteria and fungi are used in the decomposition and formation of humus
 In naturally occurring C and N cycles
Symbiotic bacteria
 present as natural flora in the intestine and vagina
Bacteria is useful to man to
 change the textures of food
 to ferment foods
 e.g. bread making and cheese making
Biotechnology
o application of scientific and engineering principles
o production of materials by biological agents
Usage of bacteria
o Sewage disposal
 digested by a combination of aerobic and anaerobic bacteria
o Fermentation industries
 Acetobacter sp. in vinegar making
 Lactobacillus sp. in milk, cheese and yoghurt products
o Antibiotics industries
 streptomyces used in production of chemicals effective in treating bacterial
infections
 streptomycin
 tetracyclines
 chloramphenicol
Factors affecting growth of microorganisms
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Nutrients
Temperatures of 20 - 45 ˚C
pH microorganisms can tolerate a higher range of pH
 some can tolerate pH of 2.5 or above 9
Oxygen
 anaerobic (very low amount of O2conditions)
 for obligate anaerobes
 aerobic – oxygen rich
 for obligate aerobes
 facultative bacteria can survive in presence or absence of oxygen
 make use of dissolved oxygen or
 chemically derived oxygen
 from chemicals like nitrates and sulphates
Osmotic Factors, Pressure, Light and Water
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Genetic Engineering and Bacteria
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Insulin is a hormone produced in the pancreas
Genetic engineering involves artificial production
 by genetically inserting the gene that codes for the hormone into a bacteria
 E.g. Escherichia coli
 Bacteria then synthesise hormones
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as if it is part of its own material
 Hormone then harvested
Insulin Production
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People suffering from Type I diabetes usually cannot control the amount of
sugar in their blood.
 Insulin is needed to treat such patients
 Insulin converts excess sugars into glycogen
 a type of carbohydrates
 stored in the body
Previously patients given insulin hormones from pigs and cows
many diabetics develop antibodies against animal insulin after prolonged
treatment
 Animal insulin is not the same as human insulin
Diseases may be transmitted from animals to humans who use animal insulin
Insulin produced by genetic engineering will not cause the above problems
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Plasmid is a tiny circular piece of DNA that occurs in bacteria.
Restriction endonuclease
 Enzyme used to cut the plasmid and human DNA to obtain the gene
Gene and plasmid are joined
 at the sticky ends by DNA ligase
Bacterium is induced to accept the plasmid

soak bacteria in ice-cold calcium chloride and incubate them at 42˚C for 2
minutes.
bacterium which has taken up the plasmid now contains recombinant DNA.
How do we know which bacteria contain recombinant DNA?
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Besides insertion of desired gene for manufacture of product (e.g. insulin)
Another gene that confers antibiotic resistance can also be inserted
Culture the bacteria on agar plates containing the antibiotic
 Bacteria with the modified plasmid will survive and grow
Colonies of recombinant bacteria can be identified
Pure cultures of the recombinant bacteria can be cultivated
Recombinant bacteria are grown in fermenters for mass production of insulin
In 10 hours, one transgenic bacterium can produce over a million copies of itself
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