Download LS 204 Microbiology Chapter 7

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LS 204 Microbiology Chapter 7 Student Learning Outcomes:
• 1. Name some organisms that are microorganisms
• 2. Explain the importance of microorganisms to our everyday lives
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3. Describe the importance of and differences between D
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viruses, viroids, and prions
• 4. Discuss why it is important to understand the growth requirements, metabolism, and genetics of bacteria
• 5. Explain how microbes cause disease and how we control them, both inside and outside of the body
Questions starting:
• What sorts of organisms would be called microorganisms – give examples
• What are some ways we benefit from microbes?
• What is a virus?
• How do bacteria divide?
• What are some ways the human body defends itself against disease?
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Examples of microorganisms of 3 Domains (Fig. 7.1):
• Bacteria
Archaea
Eukarya
Example microorganisms of the three Domains • Domain Archaea = prokaryotes; ‘extremophiles’; Halobacterium; Pyrococcus
No human pathogens; many unusual metabolic patterns
• Domain Bacteria = prokaryotes; Escherichia coli, Staphylococcus aureus; Bacillus anthracis
Beneficial organisms and human pathogens;
also unusual metabolic patterns
• Domain Eukarya: •
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Kingdom Protista – pathogens like Amoeba, Trypanosoma, Kingdom Fungi – pathogens include yeast like Candida
Kingdom Animalia – worms include Schistosoma
Kingdom Plantae – algae like Chlamydomonas
Importance of microorganisms
• Pathogens cause disease in humans, other organisms
• Beneficial organisms: • cyanobacteria and algae in oceans do photosynthesis and produce sugar and oxygen
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• fungi and Bacteria recycle waste products, organic molecules, oil spill
• fungi and Bacteria produce food and drinks (yoghurt, beer, wine)
• normal microbiota = microbes on our skin, digestive system that protect from pathogens
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Naming microbes
• Bacteria = Domain Bacteria;
• bacteria = prokaryotes, includes Domain Archaea
• 1 bacterium, 2 bacteria
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Binomial nomenclature: Species genus ex. Escherichia coli
Spell out genus first time it’s used, Afterwards, can abbreviate: E. coli
Write names in italics
Hierarchy in Domain Bacteria
• The groupings help understand shared characteristics, antibiotics that will kill them
• Ex
Ex. E. coli is Domain Bacteria, Phylum E coli is Domain Bacteria Phylum
Proteobacteria; Family Enterobacteriaceae
• Family includes other intestinal inhabitants and pathogen genera such as Salmonella, Enterobacter, Shigella)
Names can reflect shapes, sizes, arrangement of cells
• Coccus (cocci plural) = round • Bacillus (bacilli) = rod
• Spirilla = spiral‐shaped
• Strepto = chains
• Staphylo = clusters
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• Diplo‐ = two
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Names can indicate properties
• Escherichia coli Eponym for Dr. Escher; coli for colon
• Micrococcus roseus
small red circles
• Mycobacterium tuberculosis
waxy cell walls causes tuberculosis (tubercles in lungs)
waxy cell walls, causes tuberculosis (tubercles in lungs)
• Streptococcus pneumonia
round cells in chains, causes pneumonia
• Bacillus megaterium
• Thiobacillus
very large rod‐shaped organism
rod‐shaped organism that eats sulfur
More microbes: Viruses, Viroids, Prions
HPV
• Not considered ‘living’ since not cells,
lack ability to reproduce on own (use host resources).
• Virus (Fig. 7.4) has nucleic acid (DNA OR RNA) wrapped in ( g
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protein coat
• Some also have envelope (made of host’s membrane
with viral proteins)
• [Bacteriophages infect bacteria]
• Animal viruses infect animals
Virus examples
Shapes of virus capsids
herpesvirus
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Virus quantification
Plaque assay – grow viruses on lawn of susceptible host cells; Infection of host cell, replication and infection of adjacent cells ‐> hole or plaque
Virus life cycle (Fig. 7.4):
• Attachment: specific molecules on virus and receptors on host
• Penetration: all or some of virus enters
• Uncoating: protein coat removed
• Biosynthesis: of viral nucleic acids and Bi
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proteins
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mRNA ‐> proteins using host ribosomes; •
DNA or RNA of genome is reproduced
• Release: virus breaks out of cell or buds through membrane
Virus life cycle (Fig. 7.4)
Herpesvirus
A DNA virus
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Retrovirus life cycle (Fig. 7.4)
HIV (Human immunodeficiency virus)
A retrovirus: RNA genome, converts to DNA
• Viroid :
nucleic acid only – some plant diseases
• Prions – only protein – animal diseases:
• Spongiform encephalopathy (Mad Cow disease, elk wasting disease) Creutzfeld‐Jacob disease (CJD)
Examples of microorganisms of 3 Domains (Fig. 7.1):
• Bacteria
Archaea
Eukarya
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How bacteria work
tiny factories of only 1 cell compartment
• Growth and nutrition:
• Divide by binary fission
(Fig. 7.5) – 1 cell ‐>2 cells ‐> 4 cells
• Many different metabolic, nutrition patterns –
more diverse than eukaryotes
• Latin terms refer to metabolic patterns:
How bacteria work
tiny factories of only 1 cell compartment
• Producers include Photoautotrophs
(photosynthesis, use CO2 + H2O to make sugars + O2)
cyanobacteria
• Human pathogens are mostly Mesophiles
(grow at middle temperatures) • Some bacteria are thermophiles (high temperatures)
• Some bacteria are psychrophiles (low temperatures)
Oxygen requirements:
• obligate aerobes (skin, lungs)
– Pseudomonas aeruginosa
• facultative anaerobes (gut) – Escherichia coli
• obligate anaerobes (puncture wound)
– Clostridium tetani
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• Metabolism: similar to eukaryotes, especially for pathogens, but only 1 compartment
• Catabolism to take apart molecules and gain ATP building blocks;
ATP, building blocks; • Anabolism uses ATP and small molecules to build macromolecules
Typical metabolism:
Glycolysis: 6C sugar (glucose) ‐> to 3‐C pyruvate + ATP + NADH (e‐ carriers)
• occurs in cytoplasm of bacteria and eukaryotes
Krebs cycle (citric acid cycle): 3‐C pyruvate ‐> CO2 + ATP + NADH + FADH2
Electron transport chain (aerobic respiration):
• NADH + FADH2 + O2 ‐> lots of ATP + H2O + NAD + FAD
• Occurs in cytoplasm of bacteria; mitochondria of eukaryotes
Metabolism cont.
Fermentation: alternative path that does not require oxygen: occurs in cytoplasm
• Pyruvate ‐> an organic molecule; a low energy path that recycles the NADH
• Yeast make alcohol + CO2; (muscle cells lactic acid)
• Bacteria make lactic acid, butyric acid, other products
• (Fig. 7.6 concept map of relationships of pathways)
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Microbial Genetics
DNA ‐> RNA ‐> protein (Fig. 7.7)
• Transcription is
DNA copied into rRNA, tRNA or mRNA
• Translation is synthesis of protein
from mRNA on the ribosome
Examples of microorganisms of 3 Domains (Fig. 7.1):
• Bacteria
Archaea
Eukarya
Bacterial gene transfer
Bacteria can transfer some genes from one to another (even between species) (Fig. 7.8):
• Transformation = piece of DNA can go into another cell • Transduction = piece of bacterial DNA packaged in bacteriophage coat goes into other cell
• Conjugation = two bacteria attach and one donates copy of some genes
*** Antibiotic‐resistant bacteria can transfer these genes to other bacteria
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Bacterial gene transfer
methods
Microbial control – how we control them.
• Physical and chemical agents:
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Disinfectants
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Sterilants (gas, autoclave) •
Sanitizers •
Radiation
• Chemotherapeutics (antibiotics) –
compounds taken inside us to kill them
Principles of disease
• Each pathogen has its niche – temperature, humidity, cell type, oxygen
• Epidemiology – study of epidemics, or sudden large numbers of cases of disease in population.
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• Epidemiologists look for patterns of disease, moniter
numbers
• Note Latin terms, name of disease for body part: •
meningitis = inflammation of meninges
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bacteremia = bacteria in the blood system
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Defenders against disease (Table 7.9)
• Innate immunity (nonspecific)
• First line = intact skin, mucus membranes, normal microbiota
• Second line = natural killer cells
phagocytic white blood cells,
inflammation, fever
Adaptive (specific) immunity
• Specialized lymphocytes: T cells and B cells
• Antibodies produced by B cells circulate in blood stream
• Antibodies recognize Antibodies recognize
specific antigens (structures) on the pathogen
• Vaccines stimulate production of ‘memory’ T cells and B cells to defend future infection
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