Download Marine Bacteria and Archaea

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Marine Bacteria and Archaea
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Metabolic diversity
• Organisms have two fundamental nutritional needs:
•
1. Obtaining carbon in a form that can be used to
synthesize fatty acids, proteins, DNA, and RNA
• Autotrophs get their carbon from CO2
• Heterotrophs get carbon from organic sources
vs
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Metabolic diversity
•
Organisms have two fundamental nutritional needs:
•
2. Acquiring chemical energy in the form of ATP
•
Phototrophs: energy from light
•
Lithotrophs (or Chemotrophs): energy from inorganic chemicals
such as H2S, ammonia NH3, methane CH4
•
Organotrophs: energy from organic sources, such as sugars
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Metabolic diversity
Category
Energy source Carbon source
Hydrogen or
electron source
Examples
Photolithoautotrophy
Light
CO2
Inorganic
Cyanobacteria,
purple sulfur
bacteria
Photoorganoautotrophy
Light
Organic compounds Organic compounds Purple non-sulfur
bacteria, aerobic,
or H2
anoxygenic bacteria,
archaea (?)
Chemolithoautotrphy
Inorganic
CO2
Chemoorganoautotrophy
Organic
compounds
Organic compounds Organic compounds Wide range of
bacteria and
archaea
Mixotrophy (combination
of lithoautotrophy and
organoheterotrophy)
Organic
compounds
Organic compounds Inorganic
Inorganic
Sulfur-oxidizing
bacteria, nitrifying
bacteria, archaea
Sulfur-oxidizing
bacteria
Evolution of life
Prebiotic
chemistry
Biological
building blocks
Amino acids
Nucleosides
Sugars
Precellular
life
4.3-3.8 bya
RNA
world
Protein
synthesis
Catalytic RNA
RNA –
Self-replicating RNA templated
translation
Early
cellular life
DNA
Lipid
bilayers
Replication Cellular
Transcription compartments
Early cells likely
had high rates
of HGT
Evolutionary
diversification
3.8-3.7 bya
LUCA
Divergence of
Bacteria and Archaea
Components of DNA
replication,
transcription, and
translation all in
place
Submarine mounds and
their possible link to the
origin of life.
Model of the interior of a
hydrothermal mound
with hypothesized
transitions from prebiotic
chemistry to cellular life
depicted
Differences between Archaea, Bacteria and Eukaryotes
Characteristic
Bacteria
Archaea
Eukaryotes
Cell type
Prokaryotic
Prokaryotic
Eukaryotic
Histones
No histones
Have proteins
similar to histones
Have histones
Introns
No introns
Some introns
Most contain
introns
Ribosome size
70S ribosomes
70S ribosomes
80S ribosomes
Cell wall
composition
Peptidoglycan
Not always present
Made of protein
(lack peptidoglycan) Plants: cellulose
plasma membrane Fungi: Chitin
Cell membrane
composition
Ester linked lipids
with D-Glycerol
(straight chain)
Ester linked lipids
with L-Glycerol
(branch chain)
Ester linked lipids
with proteinf
(straight chain)
Themes: Growth & reproduction by fission
A. Bacterium before
DNA replication.
Bacterial chromosome is
attached to the plasma
membrane.
D. New membrane grows
between the two
attachment sites.
B. DNA replication starts.
It proceeds in two
directions
C. The new copy of DNA
is attached at a
membrane site near the
parent DNA molecule.
E. Deposits of new
membrane and new wall
material extend down
into the cytoplasm.
F. The ongoing deposition
of membrane and wall
material divides the cell in
two.
Themes: conjugation
nicked plasmid
conjugation tube
A. A conjugation tube forms between a
donor and a recipient cell. An enzyme has
nicked the donor’s plasmid.
B. DNA replication starts on the nicked
plasmid. The displaced DNA strand moves
through the tube and enters the recipient
cell.
C. In the recipient cell, replication starts on
the transferred DNA.
D. The cells separate from each other; the
plasmids circularize.
Themes: Morphological diversity
• Many have flagella for swimming and pili for clinging
to surfaces
Pili
• Typical Shapes:
Cocci
Bacilli
Spirochetes
Marine bacteria
Planktonic Bacteria and Archaea
• Relatively few major clades
Bold = ubiquitous
in seawater,
others are
specialized
Roseobacter
• 25% marine bacteria
• Plankton
• Sediments
• Microbial mats
• Sea ice
• Association with animals
• Important in carbon and sulfur cycles
Marine bacterial phenotypes
•
Anoxygenic
•
•
•
•
Eg Purple phototrophs
Do not evolve Oxygen during photosynthesis
Bacteriochlorophyll as photosynthetic pigment
Many in shallow marine sediments
CO2 + H2S + H2O = (CH2O) + S + H2O
Rhodospirillum
Marine bacterial phenotypes
•
•
Oxygenic Photosynthesis
Cyanobacteria
•
•
•
•
•
•
•
Ancestors – evolution of oxygen
Chlorophyll a and accessory photosynthetic pigments
“Blue green algae” but many “red orange”
Very diverse habitats, including extreme temperatures and hypersaline environments
Plankton, sea ice, shallow sediments, microbial mats
Many carry out nitrogen fixation
Only recently grouped together (16S sequencing)
Synechococcus
Prochlorococcus
Account for between 15-40% of carbon input to ocean food webs
Marine bacterial phenotypes
•
•
Nitrifying bacteria
Major role in nitrogen cycling, especially shallow coastal sediments, and
beneath upwelling areas
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Nitrosomonas and Nitrosococcus oxidize ammonia to nitrate
•
•
Chemolithoautotrophs
Nitrosobacter, Nitrobacter, and Nitrococcus oxidize nitrite to nitrate
•
Usually chemolithoautotrophs also mixotrophs
• Chemolithotrophs
Beggiatoa
Aerobe in top few mm of
marine sediments
Uses reduced sulfur
compounds
Thioploca
Multicellular filamentous
bacteria
Upwelling
Anoxic reduction of H2S and
reduction nitrogen
Auto- or mixo-trphic
Thiomargarita
namibiensis
Largest known bacteria,
filaments with common
mucus sheath
Upwelling
Oxidizes sulfite using
nitrate
Marine Archaea
Archaea
•
Methanogens
•
•
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Anaerobic process carried out only by Euryarchaeota (major clade)
Large amount of methane is produced in marine sediments, but
disappears before oxygen zone, where methane would be reduced
Sulfate-reducing bacteria oxidize methane using sulfur
Methanosarcina
Desulfococcus
Archaea
• Extreme Thermophiles
Pyrococcus
Anaerobic chemoorganotroph
Optimal growth at 100oC
Thermococcus
Anaerobic
chemoorganotroph,
optimum growth at
800C
Archaea
• Halophiles
•
Grow in concentrations
greater than 9% NaCl
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