Lecture 10: Autotrophy/Microbial Diversity Flashcards
Chemoautotrophs
Instead of using light, these microbes use
inorganic redox reactions as sources of
energy
Also called lithoautotrophs or chemolithoautotrophs
- These organisms are able to fix CO2, but need
a source of energy
What do chemoautotrophs do?
they oxidize compounds to gain energy
- sulfur compounds (H2S, Beggiatoa)
- ammonia for nitrosomonas
- Hydrogen gas for hydrogenomonas
- Ferrous Iron for Thiobacillus ferrooxidans
lithotrophy
Oxidation of
inorganic molecules
produces energy
Energy is captured
in redox couples
Flows through
electron transport
chain to terminal
electron acceptor
Usually oxygen, sometimes sulfate
or nitrate
nitrifyers
Nitrifying bacteria
convert reduced NH4+ to Nitrite (NO2-)
Nitrosomonas
Nitrosospira
Can be further
oxidized to nitrate
(NO3)
Nitrobacter
Nitrococcus
Sulfur Oxidizers
- Oxidize sulfur,
hydrogen sulfide,
thiosulfate
Produce hydrogen
sulfate
Direct oxidation of
sulfite
What is the best studied sulfur oxidizer?
Thiobacillus
- low pH optimum
What is sulfur oxidizers’ intermediate? What does it do?
APS
- APS intermediate can
result in substrate
level phosphorylation ATP
Photoautotrophy
Organisms that can derive energy from
sunlight, carbon from CO2
There are many microorganisms that fit this description
Oxygenic photoautotrophs
Non-cyclic photophosphorylation- release O2
Cyanobacteria, green algae
Anoxygenic photoautotrophs
Cyclic photophosphorylation, no oxygen gas
Use sulfur as electron donor
Green and purple bacteria
Photosynthesis
Photosynthesis is used by many organisms to generate energy and
carbon
Plants
Many types of bacteria
Phases of photosynthesis
- Light reactions photophosphorylation
Dark reactions Calvin-Benson cycle
Photosynthesis Light reactions
Photophosphoryl
ation
Cyclic reaction
uses no other inputs besides light energy
Non-cyclic
photophosphoryl
ation generates oxygen gas, uses water
Photoreactive dyes
Bacteria use a number of different ones
Different bacterial
species used different
chlorophylls
Also, bacteriorhodopsin
used by halophilic Archaea
Rhodopsin
absorb a photon, change the shape of the retinal in the center of the photoreceptor,
Calvin Benson Cycle
Light-independent or
dark reactions
End result is the
production of
glucose for use in
cell metabolism
This is carbon
“fixation”
Cost of CB cycle is
18 ATP and 12
NADPH
This process or the
reverse TCA cycle
can occur in bacteria
Photoheterotrophy
Organisms that use light for energy source, but are unable to fix CO2
Bacteria of this type must use organic carbon as a source of cell material
Purple non-sulfur bacteria
-> Rhodopseudomonas
Green non-sulfur bacteria
-> Chloroflexus
Evolutionary History
4.6 bya – earth
cools
3.5-3.8 bya – first
unicellular life forms
(stromatolites)
Clear microbe
fossils ~ 2 bya
First eukaryote ~
1.4 bya
First eukaryotic cell
Archaea and
Bacteria lived for
~2 by before first
eukaryote
Most popular
theory –
Endosymbiont
(Margulis)
Nucleus
Mitochondria
Chloroplast
three domains of life
- bacteria
- archaea
- Eukarya
All living things are classified using
the ______ system, developed by
the Swedish botanist ____________
- Linnaean
- Carolus Linnaeus
Candidate Phyla Radiation
- discovered after people stopped throwing away all 0.2 micron groups that were filtered out and began actually studying them.
Archaea
- physiologically similar to bacteria
- evolutionarily ancient divergence
- crenarchaeota
- euryarchaeota
- extremophiles
- methanogens
Archaeal Cell Envelope
ether-linked lipids
- G+ or - structure
pseudo-murein
similar to peptidoglycan
- N-acetyltalosaminuronic acid
- B-1,3-glycosidic bond
- different peptide junctions
Archaeal Metabolism
- dont use emden-meyerhoff glucose oxidation
- Methanogens don’t catabolize glucose
Halophiles use modified Entner- Douderoff
Autotrophy is widespread
Fix CO2, use reductive TCA cycle rather than Calvin Benson
methanogens
Strict anaerobes
Within phylum
Euryarchaeota
Can start from CO2 and H2, or intermediates
5 orders
27 genera
Lots of variation
thermoplasma
Thermoacidophiles
Lack cell wall
3 genera/families
Extreme thermophiles
Pyrococcus
Paleococcus
Thermococcus
Reduce Sulfur to
Sulfide
Extreme Halophiles
Class Halobacteria
Includes 15 genera
Require at least
1.5 M NaCl to grow
Halobacterium
salinarium (H.
halobium)
Photosynthetic
No chlorophyll
Purple membrane
Bacteriorhodopsin
Uncultured Bacteria
Many clades have
few/no cultured
representatives
Some of the most
common organisms
on earth are rarely
if ever cultivated
Candidate Phyla Radiation
bacteria pass thru 0.2 micron
filters
