Lecture 10: Autotrophy/Microbial Diversity

Question 1

Chemoautotrophs

Answer 1

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

Question 2

What do chemoautotrophs do?

Answer 2

they oxidize compounds to gain energy
- sulfur compounds (H2S, Beggiatoa)
- ammonia for nitrosomonas
- Hydrogen gas for hydrogenomonas
- Ferrous Iron for Thiobacillus ferrooxidans

Question 3

lithotrophy

Answer 3

 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

Question 4

nitrifyers

Answer 4

 Nitrifying bacteria
convert reduced NH4+ to Nitrite (NO2-)
 Nitrosomonas
 Nitrosospira
 Can be further
oxidized to nitrate
(NO3)
 Nitrobacter
 Nitrococcus

Question 5

Sulfur Oxidizers

Answer 5

• Oxidize sulfur,
  hydrogen sulfide,
  thiosulfate
   Produce hydrogen
  sulfate
   Direct oxidation of
  sulfite

Question 6

What is the best studied sulfur oxidizer?

Answer 6

Thiobacillus
- low pH optimum

Question 7

What is sulfur oxidizers’ intermediate? What does it do?

Answer 7

APS
- APS intermediate can
result in substrate
level phosphorylation ATP

Question 8

Photoautotrophy

Answer 8

 Organisms that can derive energy from
sunlight, carbon from CO2
 There are many microorganisms that fit this description

Question 9

Oxygenic photoautotrophs

Answer 9

 Non-cyclic photophosphorylation- release O2
 Cyanobacteria, green algae

Question 10

Anoxygenic photoautotrophs

Answer 10

 Cyclic photophosphorylation, no oxygen gas
 Use sulfur as electron donor
 Green and purple bacteria

Question 11

Photosynthesis

Answer 11

 Photosynthesis is used by many organisms to generate energy and
carbon
 Plants
 Many types of bacteria

Question 12

Phases of photosynthesis

Answer 12

• Light reactions photophosphorylation
   Dark reactions Calvin-Benson cycle

Question 13

Photosynthesis Light reactions

Answer 13

 Photophosphoryl
ation
 Cyclic reaction
uses no other inputs besides light energy
 Non-cyclic
photophosphoryl
ation generates oxygen gas, uses water

Question 14

Photoreactive dyes

Answer 14

 Bacteria use a number of different ones
 Different bacterial
species used different
chlorophylls
 Also, bacteriorhodopsin
used by halophilic Archaea

Question 15

Rhodopsin

Answer 15

absorb a photon, change the shape of the retinal in the center of the photoreceptor,

Question 16

Calvin Benson Cycle

Answer 16

 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

Question 17

Photoheterotrophy

Answer 17

 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

Question 18

Evolutionary History

Answer 18

 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

Question 19

First eukaryotic cell

Answer 19

Archaea and
Bacteria lived for
~2 by before first
eukaryote
 Most popular
theory –
Endosymbiont
(Margulis)
 Nucleus
 Mitochondria
 Chloroplast

Question 20

three domains of life

Answer 20

• bacteria
• archaea
• Eukarya

Question 21

All living things are classified using
the ______ system, developed by
the Swedish botanist ____________

Answer 21

• Linnaean
• Carolus Linnaeus

Question 22

Candidate Phyla Radiation

Answer 22

• discovered after people stopped throwing away all 0.2 micron groups that were filtered out and began actually studying them.

Question 23

Archaea

Answer 23

• physiologically similar to bacteria
• evolutionarily ancient divergence
• crenarchaeota
• euryarchaeota
• extremophiles
• methanogens

Question 24

Archaeal Cell Envelope

Answer 24

ether-linked lipids
- G+ or - structure

Question 25

pseudo-murein

Answer 25

similar to peptidoglycan
- N-acetyltalosaminuronic acid
- B-1,3-glycosidic bond
- different peptide junctions

Question 26

Archaeal Metabolism

Answer 26

• 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

Question 27

methanogens

Answer 27

 Strict anaerobes
 Within phylum
Euryarchaeota
 Can start from CO2 and H2, or intermediates
 5 orders
 27 genera
 Lots of variation

Question 28

thermoplasma

Answer 28

 Thermoacidophiles
 Lack cell wall
 3 genera/families

Question 29

Extreme thermophiles

Answer 29

 Pyrococcus
 Paleococcus
 Thermococcus
 Reduce Sulfur to
Sulfide

Question 30

Extreme Halophiles

Answer 30

 Class Halobacteria
 Includes 15 genera
 Require at least
1.5 M NaCl to grow
 Halobacterium
salinarium (H.
halobium)
 Photosynthetic
 No chlorophyll
 Purple membrane
 Bacteriorhodopsin

Question 31

Uncultured Bacteria

Answer 31

 Many clades have
few/no cultured
representatives
 Some of the most
common organisms
on earth are rarely
if ever cultivated

Question 32

Candidate Phyla Radiation

Answer 32

bacteria pass thru 0.2 micron
filters