BIO 315 Lecture Notes - Lecture 5: Phototroph, Sponge, Nanoarchaeota
6 Jun 2018
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Lecture 5: Archaea
Distinctive Properties of Archaea
• Archaeon "look" like bacteria but differ genetically
• Live in some of the most inhospitable places on Earth
• Group of single-celled organisms that have different characteristics which separates
them from bacteria
• First-discovered archaea were extremophiles
• Survive high temp., often above 100°C in geysers, black smokers, and oil wells
• Other common habitats include very cold habitats and highly saline, acidic or
alkaline water
• Large numbers found throughout the world's oceans in non-extreme habitats
among the plankton community
• Represent 20% of microbial cells in the oceans
• Phylogeny:
• Comparisons of rRNA gene sequences can establish phylogenetic "trees"
• rRNA has large and small subunit
o Large subunit acts as ribozyme
o In bacteria: large is 50s and small is 30s
o In eukaryotes: large is 60s and small is 40s
• The first portion termed "archaeon" were the methanogens-a poorly
characterized group of microbes capable of producing methane as a byproduct
under anoxic conditions (little to no oxygen)
Examples of Archaea in Extreme Environment
Morphology of Archaeal Cells
• Generally 0.5-5µm in diameter
• Can vary greatly (N. equitans= 0.4µm in diameter, Thermoproteus spp. can be 100µm
long)
find more resources at oneclass.com
find more resources at oneclass.com
• Nanoarchaeum equitans and ignicoccus hospitalis grow together ut sientists don’t
know why
• Shapes can vary:
• Rods, spheres, spirals
• Irregular shapes (Sulfolobus spp.)
• Rectangular shapes (Thermoproteus spp.)
Properties of Archaea:
• Both archaea and bacteria usually possess singular, circular chromosomes and lack a
membrane-bound nucleus
• DNA base pair: 0.5m bp-5m bp
• Many of the DNA replication enzymes and for replication, transcription and
translation of are more similar to eukarya in comparison to bacteria
• Archaeal plasmids
Archaeal Cell Structure
• The Cytoplasm
• Archaeal DNA is complexed with histones
• Histones form structures that DNA wraps around
• In eukaryotes 4 types of histones are present: H2A, H2B, H3, H4 which form a
octamer
• In archaea 2 types of histones are present in two copies: H3 and H4 which form a
tetramer
• Histone structure/wrapping is different in archaea from eukarya
o In eukaraya: 160-nucleotide-pair length of DNA and octamer of histone
protein
o In archaeal: 60-nucleotide-pair length of DNA and tetramer of histone
protein
• Inclusion bodies such as gas vacuoles have been observed in some archaea
• The Cytoskeleton
• Cytoskeletal homologues are found in both bacteria and archaea
• Ta0583 is an actin homolog in Thermoplasma acidophilum that resembles
eukaryal actin
• Cytoskeletal proteins from M. thermoautotrophicum and M. kandleri more
closely resemble bacterial cytoskeletal proteins
• Plasma Membrane
• All possess a plasma membrane
• Different bilayer construction
• Can even be a monolayer instead of a bilayer
o In this case, each lipid has a phosphoglycerol molecule on both ends
o This is often seen in archaeon living in high-temperature environments due
to its stability
• Ignicoccus seems to have an outer membrane and periplasm (similar
arrangement to Gram-negative cells)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Distinctive properties of archaea: archaeon look like bacteria but differ genetically, group of single-celled organisms that have different characteristics which separates. In bacteria: large is 50s and small is 30s. In eukaryotes: large is 60s and small is 40s: the first portion termed archaeon were the methanogens-a poorly characterized group of microbes capable of producing methane as a byproduct under anoxic conditions (little to no oxygen) Archaeal cell structure: the cytoplasm, archaeal dna is complexed with histones, histones form structures that dna wraps around. In eukaryotes 4 types of histones are present: h2a, h2b, h3, h4 which form a octamer. In archaea 2 types of histones are present in two copies: h3 and h4 which form a tetramer: histone structure/wrapping is different in archaea from eukarya. In eukaraya: 160-nucleotide-pair length of dna and octamer of histone protein. In archaeal: 60-nucleotide-pair length of dna and tetramer of histone protein.
