Bacteria and Archaea

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Bacteria and Archaea

• Chapter 27

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Types of Bacteria and Archaebacteria
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Bacteria and Archaea

• Diverse, abundant, and ubiquitous
• Most of the microbes (microscopic organisms) are
  bacteria or archaea
• Virtually all are unnamed and undescribed
• The total number of individual bacteria and
  archaea alive today at 5 ? 1030
• As much carbon in these cells as there is in all
  of the plants on Earth

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Bacteria and Archaea

• Bacteria and Archaea form two of the three
  domains of the tree of life

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Bacteria

• Prokaryotic
• Cell walls made of peptidoglycan
• Plasma membranes
• Distinct ribosomes
• RNA polymerase
• Can cause human disease

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Archaebacteria

• Prokaryotic and unicellular
• Call walls made of polysaccharides
• Unique plasma membranes
• Ribosomes and RNA polymerase similar to those of
  eukaryotes
• No Known to cause human disease

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Extremophiles

• Bacteria or archaea that live in high-salt,
  high-temperature, low-temperature, or
  high-pressure habitats
• Archaea are abundant forms of life in hot springs
  at the bottom of the ocean
• Water at 300C emerges and mixes with 4C
  seawater
• Enzymes that function at low temperature or high
  temperature are of commercial use

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Cyanobacteria

• No free molecular oxygen existed for the first
  2.3 billion years of Earth's history
• Cyanobacteria, were the first organisms to
  perform oxygenic photosynthesis

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Cyanobacteria

• Responsible for a fundamental change in Earths
  atmosphere
• From an atmosphere dominated by nitrogen gas and
  carbon dioxide to one dominated by nitrogen gas
  and oxygen
• Certain species of cyanobacteria can fix nitrogen
• Form close association
• with plant roots
• Symbiotic relationship

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Classification and Study of Bacteria
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Studying Bacteria and Archaebacteria

• Biologists use several research strategies to
  answer questions about these species
• Nutrient enriched agar
• Based on establishing a specific set of growing
  conditions per bacteria
• Used to isolate new types of bacteria and archaea

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Studying Bacteria and Archaebacteria

• Direct sequencing - strategy for documenting the
  presence of bacteria and archaea that cannot be
  grown in culture and studied in the laboratory

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Evaluating Molecular Phylogenies

• A tree of life based on morphology had only two
  divisions prokaryotes and eukaryotes

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Evaluating Molecular Phylogenies

• The tree of life based on ribosomal RNA sequences
  shows three domainsArchaea, Bacteria, and
  Eukaryaand is now accepted as correct
• The first lineage to diverge from the common
  ancestor was the Bacteria
• Archaea and Eukarya are more closely related to
  each other than to the Bacteria

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Evaluating Molecular Phylogenies
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Major Clades of Bacteria
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Classifying Bacteria
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Diversity of Bacteria

• Bacteria and Archaea have diversified into
  hundreds of thousands of distinct species
• Overall patterns and themes help biologists make
  sense of the diversity
• The sizes, shapes, and motility of Bacteria and
  Archaea can vary greatly

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Diversity of Bacteria and Archaea
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Gram Staining

• Gram staining distinguishes bacteria by the type
  of cell wall

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Bacterial Reproduction

• Bacteria and archaea reproduce by fission
• Splitting of cells
• Bacterial cells can transfer copies of plasmids
  extra-nuclear loops of DNA
• During conjugation, a copy of a plasmid moves
  from one cell to a recipient cell
• Conjugation tube is a morphological trait that is
  unique to bacteria and archaea

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Conjugation
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Metabolic Diversity

• Bacteria and Archaea produce ATP in three ways
• Phototrophs can use light energy. ATP is produced
  by cellular respiration.
• Organotrophs oxidize reduced organic molecules.
  ATP is produced by cellular respiration or
  fermentation

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Metabolic Diversity

• Lithotrophs oxidize inorganic molecules. ATP is
  produced by cellular respiration with the
  inorganic compound serving as the electron donor
• Autotrophs manufacture their own
  carbon-containing compounds heterotrophs live by
  consuming them

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Cellular Respiration Variation in Bacteria

• In cellular respiration
• a molecule with high potential energy serves as
  an electron donor and is oxidized
• a molecule with low potential energy serves as a
  final electron acceptor and is reduced
• The potential energy difference is converted
  into ATP
• Bacteria and archaea can exploit a wide variety
  of electron donors and acceptors

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Cellular Respiration Variation in Bacteria
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Cellular Respiration Variation in Bacteria
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Cellular Respiration Variation in Bacteria

• Fermentation is a strategy for making ATP without
  using electron transport chains
• No electron acceptor is used redox reactions are
  internally balanced
• Lactic acid fermentation
• Alcoholic fermentation

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Key Lineages of Bacteria and Archaea
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Lineages of Bacteria

• There are at least 14 major lineages (phyla) of
  bacteria
• Spirochetes have a corkscrew shape and unusual
  flagella
• Chlamydiales are spherical and very tiny
• Live as parasites inside animal cells

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Lineages of Bacteria

• High-GC (guanine and cytosine) Gram-positive
  bacteria have various shapes
• Many soil-dwelling species form mycelia (branched
  filaments)

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Lineages of Bacteria

• Cyanobacteria are autotrophic
• Produce an abundance of oxygen and nitroge
• Also produce many organic compounds, that feed
  other organisms in freshwater and marine
  environments

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Lineages of Bacteria

• Low-GC Gram-positive bacteria cause a variety of
  diseases including anthrax, botulism, tetanus,
  gangrene, and strep throat
• Lactobacillus is used to make yogurt

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Lineages of Bacteria

• Proteobacteria cause Legionnaires disease,
  cholera, dysentery, and gonorrhea
• Certain species can produce vinegars. Rhizobium
  can fix nitrogen

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Archaea Lineages

• Archaea live in virtually every habitat,
  including extreme environments
• Crenarchaeota are the only life-forms present in
  certain extreme environments, such as
  high-pressure, very hot, very cold, or very
  acidic environments

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Archaea Lineages

• Euryarchaeota live in high-salt, high-pH, and
  low-pH environments
• Include the methanogens, which contribute about 2
  billion tons of methane to the atmosphere each
  year