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Andrew Hoff
Microbiology
Exam #4
Extra credit
I.
Archaea
Eubacteria
Cell wall chemistry
no murein
Transfer RNA
no thymine
typical sacculus
(murein present)
thymine
Introns/Exons
present
absent
#of RNA polymerase types
several
one
Polymerase type 2 promoters
yes
no
Membrane lipids
ether linkages
ester linkages
Methanogenesis
yes
no
Chlorophyll based synthesis
no (bacteriorhodopsin)
yes
Tendency to occupy
harsh environments
yes (halophilic,thermophilic)
lesser (acidophilic)
2. Carl Woess worked with thermophiles/extremophile such as methanogens that live in the
intestines and mud. He looked for phylogenetic similarities in G-C ratios, cytochromes, and
isozymes. A unique comparison that he identified was in the 70s ribosome, more specifically the
30s subunit. Two thirds of the mass of this subunit is 16s RNA, which is ahighly conserved
sequence complementary to any tRNA bringing in an amino acid. Woess compared Archaea
with Eubacteria by isolating RNA, separating them, transferring the “oligo” pieces and
separating them, an end result being an association coefficient which tells how similar and
how different particular strands are. He basically did a nucleotide fingerprint with both and
found significant parts were similar. These nucleotide fingerprints could be graphed and
compared to test homology of the 16s subunit. A result of his work was finding that Achaean
bacteria are as different from eubacteria as we are from eubacteria. His work is important in
sorting out prehistorical details of the evolution of bacteria and eukaryotes from the common
Achaean ancestor.
III.
Group 1. Methanogens (i.e. Methanococcus)
Produce methane in large quantities
Anaerobes
Use simple substrates such as hydrogen, acetate and methanol
Major green house gas producer
These archaea would have used simple substrates present on early earth and helped to make
an atmosphere.
Group 2. Extremely Halophilic (i.e. Halobacterium)
Live in high salt concentrations
Can be Gram (-) or (+)
Aerobic or facultatively anaerobic chemoorganotrophs
May have bacteriorhodopsin to produce light form ATP
Mesophilic
These could live in salty waters (such as oceans) and produce ATP from light.
Group 3. Sulfate Reducers (Archaeoglobus)
Make hydrogen sulfide form sulfate from dissimilatory sulfate reduction.
Thermophiles
Anaerobic
May be found around vents
Early earth had high sulfur concntrations because of all the volcanic activity. These archaea
could use this as an electron source to make ATP.
Group 4. Thermophilc Sulfur Metabolizers (Thermococcus)
Obligate thermophiles living in 70-105 Celsius environments
Autotrophic or heterotrophic
Thermicus aquaticus –TAQ polymerase is able to replicate DNA at high temperatures with
out denaturing. Implications for PCR technique.
Early earth was very hot and these bacteria could replicate at high temps without suffering
from denaturing proteins.
Group 5. Cell-Wall Less (Mycoplasma)
Coccoid cells lacking a cell envelope
Thermoacidophilic
Aerobic
Refractory – hard to treat w/ antibiotic
May have sterols in cell wall
Pleomorphic
Highly mutable
Very small – filtrable
These are hard to destroy due to the lack of a cell wall. This means that many antimicrobials
are ineffective. These bacteria would be resistant to ammensalism. Since they are also highly
mutable they may have helped with organism/species proliferation