Transcript Bacteria

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
• 3. Describe the importance of and differences between
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?
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
• 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
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. 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
•
• Diplo- = two
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)
• 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
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
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
proteins
•
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
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
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
• Metabolism: similar to eukaryotes, especially
for pathogens, but only 1 compartment
• Catabolism to take apart molecules and gain
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)
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
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)
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Sanitizers
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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.
• Epidemiologists look for patterns of disease, moniter
numbers
• Note Latin terms, name of disease for body part:
•
meningitis = inflammation of meninges
•
bacteremia = bacteria in the blood system
Defenders against disease
• Innate immunity (nonspecific)
• First line = intact skin,
mucus membranes,
normal microbiota
• Second line =
natural killer cells
phagocytic white blood cells,
inflammation, fever
(Table 7.9)
Adaptive (specific) immunity
• Specialized lymphocytes:
T cells and B cells
• Antibodies produced by B cells
circulate in blood stream
• Antibodies recognize
specific antigens (structures)
on the pathogen
• Vaccines stimulate
production of ‘memory’
T cells and B cells
to defend future infection