ARCHAEA Dr. G. M. Mohiuddin MD Resident Phase-A, Year-2 Dept. of Microbiology & Immunology, BSMMU

Introduction Greek αρχαία means “Old ones”. In the past they had been classed with Bacteria as Prokaryotes (or Kingdom Monera) and named Archaebacteria. In 1977, Woese and Fox proposed the Archaea as a third domain of life based on ssrRNA sequence cataloguing. Present as single cell or in Aggregated or filaments.

Present in extreme environments (Extremophiles) Area with High or low temperature. Area with high salt concentration Area with high Methane concentration Area with no oxygen

Morphology Present as single cell or in Aggregated or filaments. Size: Length: 1 to 200 micrometer Diameter: 0.1 to 15 micrometer Shape: Coccus, Bacillus, Spirillium, Plate like & Pleumorphic.

Fig: Bacterial cell wall

Fig: Archaeal cell wall

Traits Bacteria Archaea Eukaryota Cell Type Prokaryotic Eukaryotic Cell wall Peptidoglycan Present Absent Membrane lipid Straight Carbon chains attached to Glycerol by Ester linkage Branched Carbon chains attached to Glycerol by Ether linkage Membrane bound organelle Plasmid Ribosome 70S 80S rRNA Loop First Amino acid in protein synthesis Formylmethionine Methionine Antibiotic Sensitivity Sensitive Resistance Membrane enclosed Nucleus DNA Histone Cell Division Binary division Mitosis or miosis

Major Archaeal Groups Thermophilic Archaea Halophilic Archaea Methanogenic Archaea Archaeal Sulphate Reducers Cell wall less Archaea

Thermophilic Archaea Can survive at 70-1100C Usually strict anaerobe. Some are aerobic & facultative. Enzymes needs high temperature for their function. Eg: Thermococcus, Desulfurococcus, Sulfolobus etc.

Yellowstone National Park, USA Thermophilic Archaea Yellowstone National Park, USA

Halophilic Archaea Greek Halophiles = Salt loving Thrive in high salt concentrations (0.5 - 5M of NaCl). Eg: Haladaptatus cibarius, Halalkalicoccus jeotgali.

Great Salt lake, Utah, USA Halophilic Archaea Great Salt lake, Utah, USA

Methanogenic Archaea Strict anaerobe. They can reduce CO2 into Methane which creates an electrochemical gradient across cell membrane to produce ATP. Convert Sulfur to H2S with no energy production. Eg: Methanobrevibacter smithii, Methanobacterium, Methanococcus, Methanomicrobium.

Others Archaeal Sulphate Reducers Archeoglobus

Are they Pathogen??? As like Bacteria Archaea have been found in human gut, oral cavity & skin. They can evade, colonize even stay with normal flora in human body. But their pathogenic activity has not been established.

Importance Methanogenic Archaea produce methane using sewage sludge, which is a clean burning fuel. Reduction the number of Methanogenic Archaea is associated with Crohn’s disease. Excess methane production is contributory to global warming.

Halophilic Archaea are used in production of many salted food products (Soy sauce). DNA polymerase of Thermophilc Archaea is a great interest in molecular biology. Thermoplasma oxidize Iron sulfide (piles of coal mines) to Sulfuric acid. As a result piles become hot & acidic.

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