chapter 18. domain archaea only one kingdom: archaebacteria ▪ cells contain cell walls ▪ live...
TRANSCRIPT
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Prokaryotes: BacteriaChapter 18
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Two Domains of Bacteria
Domain Archaea Only one kingdom: Archaebacteria
▪ Cells contain cell walls▪ Live in extreme environments (hot, acidic,
salty, no O2)▪ Thermoacidophiles (example: Staphylothermus
marinus in hot sea vents; pictured below)▪ Halophiles (example: Dead Sea bacteria)▪ Methanogens (example: sewage treatment
bacteria)
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Two Domains of Bacteria
Domain Eubacteria Only one kingdom: Eubacteria
▪ Very strong cell walls containing peptidoglycan (a polymer)
▪ Cannot survive in extreme environments▪ Can be photosynthetic (autotrophs)▪ Examples:
▪ Anabaena (autotrophs) ▪ Mycobacterium tuberculosis (heterotroph)
Anabaena
Mycobacterium
tuberculosis
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Bacteria Structure
• No nucleus, just a chromosome
• Unicellular organisms. They have some characteristics of all cells, such as DNA and ribosomes.
• Lack a nuclear membrane and other membrane-bound organelles
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Bacteria Structure
• Chromosomes: large, circular and found in a nucleoid
• Capsule: secreted layer of polysaccharides outside of the cell wall that prevents the cell from drying out and helps it attach to surfaces
• Pili: tiny, hairlike protein structures that help attach to surfaces; can transfer genetic info across them
• Size: VERY small; much smaller than eukaryotic cells
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Identifying Bacteria
Three criteria: Shape Cell Wall Movement
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Identifying Bacteria: Shape
Three common bacteria shapes: Spherical = Cocci Rod-shaped = Bacilli Spiral-shaped = Spirochetes
Cocci Bacilli Spirochetes
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Identifying Bacteria: Cell Walls Gram staining: a dye is added to a
sample of bacteria; peptidoglycan is indicated with purple color
Two Categories: Gram positive: Turns purple during Gram
staining; indicates high level of peptidoglycan in the cell wall
Gram negative: Turns light pink during Gram staining; indicates a low level of peptidoglycan in the cell wall
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Identifying Bacteria: Movement
Three common modes of movement: Stationary: no movement Flagella: filament that moves like a tail
to propel the bacteria through an environment
Gliding: secrete a slime layer to glide across
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Bacteria Reproduction
Prokaryotes reproduce by: Binary Fission
▪ Division of the cell into two genetically identical cells
▪ Occurs quickly (can be every 20 minutes)
▪ 1 bacterium can become 1 billion in 10 hours
Conjugation▪ Two prokaryotes attach to each other
and exchange genetic information using pili
▪ New gene combinations result in increased diversity
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Metabolism of Bacteria
All living things require energy to carry out cellular respiration.
Two categories of obtaining energy: Heterotrophs: cannot make their own food;
must take in food from surroundings▪ Saprobes: decompose organic molecules in dead
organisms or organic waste Autotrophs: make their own food
▪ Photoautotrophs: carry out photosynthesis; require light
▪ Chemoautotrophs: break down inorganic compounds; do not require light
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Survival Mechanisms of Bacteria
How can bacteria survive when their surroundings become unfavorable? Two methods of survival:
▪ Endospores: production of a “dormant” cell▪ Mutations: new combinations of genes and
rapid reproduction
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Survival: Endospores
1.Spore coat surrounds chromosome and small cytoplasm.
2.Endospore protected if bacteria cell dies.
3.Endospore grow. (germinates)
4.New bacterial cell outgrowth.
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Ecology of Bacteria
Bacteria is significant in recycling nutrients to the environment. Decomposer – Breaks down dead
organisms to return organic compounds to the environment.
Nitrogen-fixing – Converts N2 gas in the atmosphere to NH3 (ammonia); allows nitrogen to be taken into the food chain via plants; N is key in amino acids therefore proteins.
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Good Bacteria
Most of the bacteria that live in or on you are harmless and are called normal flora.
E. coli 21,674x
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Good Bacteria
Some food are made with the aid of bacteria: Cheese Yogurt Buttermilk Pickles Vitamins Chocolate
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Pathogens – Bad Bacteria
Disease-causing bacteria are called pathogens.
Antibiotics are used to treat bacterial infections.
Body Story - Salmonella