Archaea: Characteristics and Classification

Methanogens: Methane Makers

• Obligate anaerobes that produce methane (CH4) as an end product of metabolism
• Use CO2, H, and N to produce energy for living
• CO2 + 4 H2 → CH4 + 2 H2O
• Found in anaerobic systems, including rumen of cows, human gut, marine sediments, hot springs, and marine hydrothermal vents
• Methane can be used as a fuel, but it's a greenhouse gas contributing to global warming

Extreme Halophiles

• Salt-loving microbes that require high salt concentrations (17-23% w/v NaCl) to grow
• Example: Halobacterium in Owens Salt lake
• Will not grow without high salt concentrations

Cell Wall-less Archaea

• Found in coal mine piles, causing temperatures to rise
• Cause mine dumps to become acidic due to pyrite (FeS2) formation
• Can grow at 59°C
• Shape of Thermoplasma changes after taking in liquid

Extreme Thermophiles

• Prefer temperatures between 88-113°C
• Obligate anaerobes that can 'breathe' sulfur instead of oxygen
• Both autotrophic and heterotrophic
• H2SO4 is an end product of their metabolism
• Example: Pyrolobus fumarii can grow at 113°C

Archaea Characteristics

• Shapes: spherical, rod, spiral, lobed, rectangular, irregular, flat, square
• Arrangement: single cells, filaments, clusters
• Until 1970, classified as bacteria
• Unique cell wall composition with complex polysaccharides and lack of peptidoglycan
• Presence of unusual lipids enables survival in extreme environments

Archaea Metabolism

• Organotrophs: obtain energy from organic compounds
• Autotrophs: known as "producers," making their own food from raw materials and energy
• CO2 fixers and N2 fixers

Archaea Uniqueness

• Unique cell wall composition
• Presence of unusual lipids enables survival in extreme environments
• Found in diverse range of extreme environments

Notable Archaea

• Archaeoglobus fulgidus: sulfur-reducer that can sour (H2S) oil wells
• Halobacterium: salt-loving microbes that give a pink tinge to salt water evaporation ponds, the Dead Sea, and salted fish
• Pyrolobus fumarii: led scientists to extend the upper temperature limit for life to 113°C
• Pyrococcus furiosis: source of an extra-stable enzyme used in PCR and gene sequencing
• Sulfolobus acidocaldarius: used to leach copper and iron from ore

5 Main Groups of Archaea

• Methanogens ("methane-makers")
• Archaea sulphate reducers
• Extreme halophiles ("salt lovers")
• Cell wall-less archaea
• Extreme thermophiles/psychrophiles ("heat/cold lovers")

This quiz covers the characteristics, metabolism, ecology, and taxonomy of Archaea, a domain of microorganisms that are prokaryotic and extreme-loving. It also explores their unique features and differences from Bacteria.