Microbiology 3 ch. 4, 19, 20 archaea and ribotyping and methanogens
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Who discovered archaea and how was it done?
Carl Woese. He studied the Small Subunit (SSU) rRNAs of various microbes and based on the similarities and differences between the nucleotide sequences of various microbes, he found that that were two major classes of microbes: bacteria and archaea.
what is ribotyping and how is it done?
- ribotyping is a type of genomic fingerprinting (processes
- by which restriction enzymes are used to compare the phylogenies of different
- organisms). Ribotyping begins by
- treating a microbe’s entire DNA with a restriction enzyme. The digested DNA is
- run on a gel and transferred to a nylon filter, and the rRNA encoding DNA
- fragments are visualized after hybridization with a labeled rRNA gene probe.
- Ribotyping allows for the revealing of a microbe’s identity.
Why is 16S rRNA used as the target for ribotyping?
The SSU rRNA is used as the target for this techniquebecause it plays the same role in all organisms. These nucleotide sequences arealso very resistant to mutation. The SSU rRNA is also used in this techniquebecause it contains certain regions that are variable among organisms andcertain regions that are quite similar. The variable regions can be used tocompare the evolutionary histories of two similar organisms, while the similarregions can be used to compare distantly related organisms.
how does pseudomurein differ from peptidoglycan?
pseudomurein lacks NAM, and it does not containD-amino acids, but it does however have alanine, glutamic acid and lysine, but all in the L-chiral form.
archaea and gram staining
The Archaea can be tested by Gram staining andyield both Gram+ and Gram-negative species. But there is not the samecorrelation of structure with Gram staining as found with the Bacteria. SomeGram + types have a cell wall made of pseudomurein. This is similar to butcertainly different from peptidoglycan.
how do archaeal membrane lipids differ from those of bacteria?
- 1) Theycontain hydrocarbons derived from isoprene units: five-carbon, branchedmolecules:
Because of the kink that you see in isoprene, the lipids inarchaeal membranes = branched.
2) Hydrocarbonsare attached to glycerol by ether links rather than ester links. This allowsthem to be more resistant to chemical attacks than bacteria.
3) Archaea also have diglycerol tetraether lipids in their membranes. Diglycerol tetraether lipids are formed when two glycerol residuesare linked by two longhydrocarbonsthat are 40 carbons in length. They are more rigid than diethers. Thediglycerol tetraether lipids are found in archaea that live in hotenvironments.
what are methanogens?
- . They
- are a major group of anaerobic Archaea, which obviously produce methane.
what are the two major types of methanogens?
- The two major types of methanogens are CO2
- reducers and aceticlastic methanogens. The latter means that acetic acid is
- cleaved into CO2 and methane CH4. The CO2 reducers
- use hydrogen gas to reduce the carbon dioxide to methane.
what is the difference between a methanotroph and a methylotroph?
- Any organism using one-carbon organic compound for both an
- electron donor and as a
- source of cell carbon is termed a Methylotroph
- Methanotroph - These
- are aerobic organisms that oxidize methane (CH4) using it for both an electron
- donor and as a source of cell carbon
what is an oligonucleotide signature sequence?
- An oligonucleotide signature sequence (OSS) is a
- sequence of nucleotides that is specific to a certain set of phylogenetically
- related organisms.
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