Block E Flashcards
Gram positive bacteria
cytoplasmic membrane, peptidoglycan, periplasmic space
gram negative bacteria
cytoplasmic membrane, peptidoglycan, periplasmic space, outer membrane made of lipopolysaccharide and protein
archaea
cytoplasmic membrane. more chemically and structurally diverse, semi-rigid lattice of pseudomurein, sugars, proteins or glycoproteins. NO PEPTIDOGLYCAN
how are archaea lipids unique
1 – Ether-linked lipids (not ester-linked)
2 – Side-chains are not fatty acids, but branched isoprenes
3 – Different chiral form of glycerol
4 – Some archaea possess lipid monolayers
flagella
Bacterial flagella are helical filaments that rotate providing motility
Archaeal flagella are superficially similar to bacterial flagella, but are different in many ways and considered non-homologous (convergent evolution)
Bacterial flagella are produced by the addition of flagellin subunits at the tip; archaeal flagella grow by the addition to the base
Bacterial flagella are thicker and hollow allowing flagellin sub-units to pass through
No sequence similarity being detected between the genes of the two systems
what groups are archaea split into
Euryarchaeota
Crenarchaeota
Thaumarchaeota
Korarchaeota
Nanoarchaeota
Euryarchaeota
Physiologically diverse group of Archaea, Many inhabit extreme environments, Examples: high temperature, high salt, high acid
key genera of haloarchaea
Halobacterium, Haloferax, Natronobacterium
Extremely Halophilic Archaea
Water balance in extreme halophiles
Halophiles need to maintain osmotic balance
This is usually achieved by accumulation or synthesis of compatible solutes
Halobacterium species instead pump large amounts of K+ into the cell from the environment
Intracellular K+ concentration exceeds extracellular Na+ concentration and positive water balance is maintained
Proteins of halophiles
Are highly acidic
Contain fewer hydrophobic amino acids and lysine residues
Some haloarchaea are capable of light-driven synthesis of ATP
Methanogenic Archaea
Methanogens Key genera: Methanobacterium, Methanocaldococcus, Methanosarcina
Microbes that produce CH4
Found in many diverse environments
Taxonomy based on phenotypic and phylogenetic features
Diversity of methanogens
Demonstrate diversity of cell wall chemistries
Pseudomurein (e.g., Methanobacterium)
Methanochondroitin (e.g., Methanosarcina)
Protein or glycoprotein (e.g., Methanocaldococcus)
S-layers (e.g., Methanospirillum)
Substrates for methanogens
Obligate anaerobes
11 substrates, divided into 3 classes, can be converted to CH4 by pure cultures of methanogens
Other compounds (e.g., glucose) can be converted to methane, but only in cooperative reactions between methanogens and other anaerobic bacteria
Thermoplasmatales
Key genera: Thermoplasma, Picrophilus, Ferroplasma
Taxonomic order within the Euryarchaeota
Thermophilic and/or extremely acidophilic
Thermoplasma and Ferroplasma lack cell walls
Thermoplasma
Chemoorganotrophs
Facultative aerobes via sulfur respiration
Thermophilic
Acidophilic
Found in self-heating coal piles
Ferroplasma
Chemolithotrophic
Acidophilic
Oxidizes Fe2+ to Fe3+, generating acid
Grows in mine tailings containing pyrite (FeS2)
Picrophilus
Extreme acidophiles
Grow optimally at pH 0.7
Model microbe for extreme acid tolerance
Thermococcales and Methanopyrus
Key genera: Thermococcus, Pyrococcus, Methanopyrus
Three phylogenetically related genera of hyperthermophilic Euryarchaeota
Comprise a branch near root of archaeal tree
Distinct order that contains Thermococcus and Pyrococcus
Indigenous to anoxic thermal waters
Highly motile
