bacteria and archaea the prokaryotic domains. prokaryotic complexity figure 4.5
TRANSCRIPT
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Bacteria and Archaea
The Prokaryotic Domains
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Prokaryotic ComplexityFigure 4.5
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Eukaryotic ComplexityFigure 4.7
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Prokaryotes
• derived from ancient lineages
• more biomass than all other life combined
• “simple” cellular structure
– no nuclear membrane
– no membrane-bound organelles
– no cytoskeleton
• limited morphological variation
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Prokaryotic MorphologiesFigure 27.13
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Prokaryotic Morphologies
Figure 27.1
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photosynthetic bacteriaFigure 27.7
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photosynthetic archaeaFigure 27.20
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Prokaryotes• diverse metabolic “strategies”
– photoautotrophy
– chemoheterotrophy
• most bacteria and archaea
– chemoautotrophy
– photoheterotrophy
• energy from light
• carbon from organic compounds
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Energy/carbonTable 27.2
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Prokaryotes
• in nearly every habitat on Earth– terrestrial– aerobic/anaerobic– marine/freshwater– deep ocean rifts/deep in crust (>2 km)– antarctic ice pack– hot/acidic (>100˚C; pH = 2-3)– salty/alkaline (pH = 11.5)– etc.
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Prokaryotes
• a range of growth rates
– generation times
• 10 min
• 1-3 hours
• days - weeks
– suspensions between growth periods
• indefinite
–years, decades, >century, millions?
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Prokaryotes
• Some defy taxonomic notions
– get too big
– possess internal membrane systems
– exhibit “eukaryote-like” growth forms
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Actinomycete Figure 27.16
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MorphologyFigure 27.3
Streptococcus pyogenes Staphylococcus aureusNeisseria gonorrhoeaeDiplococcus
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bacterial gas vesiclesFigure 27.4
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Prokaryotic Taxonomy• Historically
– morphology
– motility (+/-)
• rolling/gliding
• vertical positioning
• flagella & axial filaments
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axial filamentsFigure 27.4
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flagella
Figure 27.5
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Prokaryotic FlagellumFigure 4.6
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Gram’s Stain:
Bacillus subtilisgram positiveFigure 27.6
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Gram’s Stain:
E. coligram negative
Figure 27.6
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Prokaryotic Taxonomy• Historically
– morphology– motility– reactivity
• Gram’s stain - peptidoglycan cell wall• metabolism
–aerobic/anaerobic–resource utilization–products –inclusion bodies
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MycoplasmaFigure 27.17
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endospore - resting bodyFigure 27.14
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Prokaryotic Taxonomy• Historically
– distinctive features• size
–very large or very small• stress response
–endospore formation• life style
–colonial/parasitic/pathogenic
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Chlamydia: obligate intracellular parasiteFigure 27.13
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crown gall on geranium
due to Agrobacterium
tumefaciensFigure 27.10
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Prokaryotic Taxonomy• Pathogenic requirements
– contact
– entry
– defense evasion
– multiplication
– damage
– infectious transfer
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Prokaryotic Taxonomy• Pathogen characteristics
– Invasiveness
– Toxigenicity
• Corynebacterium diphtheriae vs. Bacillus anthracis
• endotoxin vs. exotoxin
–Salmonella vs. Clostridium tetani
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Prokaryotic Taxonomy• Koch’s postulates
– Always found in diseased individuals– Grown in pure culture from host inoculant– Cultured organisms causes disease– Newly infected host produces a pure culture
identical to the infective culture
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Prokaryotic Taxonomy• Historically
– distinctive features• size
–very large or very small• stress response
–endospore formation• life style
–parasitic/pathogenic• ecological niche
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Methanogens & methane using Archaea
• Methanogens release 80-90% of atmospheric methane, a greenhouse gas
• Methane users intercept methane seeping from sub-oceanic deposits
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Prokaryotic Taxonomy
• Biofilm production
– on solid surfaces
– mixed colonies
– polysaccharide matrix
– resistant to treatments
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Recent Prokaryotic Phylogeny
• Based on rRNA
– evolutionarily ancient
– shared by all organisms
– functionally constrained
– changes slowly with time
– encodes signature sequences
–BUT - yields a different phylogeny than other sequences analyzed
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Recent Prokaryotic Phylogeny
• sources of phylogenetic confusion
– Lateral gene transfer
• among members of bacterial species
• among members of different species
• across domains…
– phylogenetic analysis assumes cladogenic evolution
• evolution may have been highly reticulate
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Recent Prokaryotic Phylogeny
• sources of phylogenetic confusion
– Mutation
• prokaryotes are haploid
–“recessive” mutations are not masked
• prokaryotes have very little non-coding DNA
• many prokaryotes have very short generation times
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Recent Prokaryotic Phylogeny
• rRNA led to three domains
– Archaea: more similar to Eukarya than to Bacteria
– An ancient split between Bacteria and Archaea was followed by a more recent split between Archaea and Eukarya
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The Three Domain PhylogenyFigure 27.2
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Shared Features of the Three Domains
• plasma membrane
• ribosome structure
• glycolysis
• encode polypeptide sequences in DNA
• replicate DNA semi-conservatively
• transcribe, translate with same genetic code
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Table 27.1
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some major bacterial groups
Figure 27.8
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Bacterial Phylogeny
• Molecular comparisons suggest several higher level groups
– Proteobacteria are highly diversified
• gram negative
• bacteriochlorophyll
• source of mitochondria
• N2-fixers, Rhizobium, Agrobacterium, E. coli, Yersinia, Vibrio, Salmonella, etc.
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ProteobacteriaFigure 27.9
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Bacterial Phylogeny
• Molecular comparisons suggest several higher level groups
– Proteobacteria are highly diversified
– ancient Cyanobacteria produced oxygen and chloroplasts
• “blue-green algae”
• fix CO2 & N2
• single or colonial - sheets, filaments, balls
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Cyanobacteria fix CO2 & N2
Figure 27.11
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Cyanobacteria are pond scumFigure 27.11
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Bacterial Phylogeny
• Molecular comparisons suggest several higher level groups
– Proteobacteria are highly diversified
– ancient Cyanobacteria produced oxygen and chloroplasts
– Spirochetes have axial filaments
• human parasites & pathogens
• free living in water sediments
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Spirochetes have axial filamentsFigure 27.12
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Bacterial Phylogeny
• Molecular comparisons suggest several higher level groups
– Proteobacteria are highly diversified
– ancient Cyanobacteria produced oxygen and chloroplasts
– Spirochetes have axial filaments
– Chlamydias have a complex life cycle
• obligate intracellular parasites
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Chlamydia Figure 27.13
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Bacterial Phylogeny• Molecular comparisons suggest several higher
level groups
– Firmicutes: a diverse (mostly) Gram positive group
• some produce endospores
• some are native flora
–Staphylococcus
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Gram + staphylococci
Figure 27.15
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Bacterial Phylogeny• Molecular comparisons suggest several higher
level groups
– Firmicutes: a diverse (mostly) Gram positive group
• some produce endospores
• some are native flora
• some are filamentous (actinomycetes)
–Mycobacterium tuberculosis
–Streptomyces spp.
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filamentous ActinomyceteFigure 27.16
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Bacterial Phylogeny• Molecular comparisons suggest several higher
level groups
– Firmicutes: a diverse (mostly) Gram positive group
• some produce endospores
• some are native flora
• some are filamentous (actinomycetes)
• Mycoplasmas
–small (~0.2 µm), no cell wall, low DNA
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Mycoplasma Figure 27.17
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unique membrane structureFigure 27.18
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unique membrane structureSee page
539
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Archaean Phylogeny
• Most known archaea are extremophiles
– many are not
• Archaea cell walls lack peptidoglycan
• Archaea possess unique cell membranes lipids
• Archaea share rRNA signature sequences
• >1/2 of Archaean genes are unlike genes known from Bacteria or Eukaryotes
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Archaean Phylogeny
• Crenarchaeota
– most live in hot, acidic habitats
• 70-75˚C; pH 2-3
–Sulfolobus pH = 0.9
–Ferroplasma pH = 0.0
–some maintain internal pH 7.0
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a hot, acidic homeFigure 27.19
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Archaean Phylogeny
• Crenarchaeota
– most live in hot, acidic habitats
• Euryarchaeota
– Methanogens [CO2 => CH4]
• strict anaerobes in cow guts, rice paddies and hydrothermal vents
• all share rRNA similarities
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Archaean Phylogeny
• Crenarchaeota
– most live in hot, acidic habitats
• Euryarchaeota
– Methanogens
– extreme halophiles
• e.g. in the Dead Sea
• some use bacteriorhodopsin (retinal), not bacteriochlorophyll
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Archaean Phylogeny
• Crenarchaeota
– most live in hot, acidic habitats
• Euryarchaeota
– Methanogens
– extreme halophiles
– Thermoplasma
• thermoacidophile, no cell wall
• genome size = Mycoplasmas (1.1 x 106)