Overview
This lecture discusses Archaea, their unique characteristics, and how they differ from Bacteria and Eukarya, focusing on their adaptation to extreme environments and cellular structures.
Introduction to Archaea
- Archaea are unicellular organisms often found in extreme environments (high temperature, high salt).
- Historically called "Archaebacteria," but this is outdated as Archaea are not bacteria.
- Archaea and Bacteria are both prokaryotes (no nucleus or membrane-bound organelles).
Similarities and Differences: Archaea vs. Bacteria
- Both are unicellular, prokaryotic, and reproduce by binary fission.
- Both can be autotrophs (make their own food) or heterotrophs (consume food).
- Both have genetic material, cytoplasm, and ribosomes.
- Classified in separate domains in the three-domain system: Bacteria, Archaea, and Eukarya.
Unique Cell Structures
- Archaea have distinctive cell membranes with ether linkages, while Bacteria and Eukarya have ester linkages.
- Some Archaea have a lipid monolayer membrane, aiding survival in harsh environments.
- Archaea possess diverse cell walls without peptidoglycan; some have pseudopeptidoglycan.
- Bacteria cell walls contain peptidoglycan and can be gram positive or gram negative; most Archaea stain gram negative but lack peptidoglycan.
Genetics of Archaea
- Archaea DNA is generally circular, like Bacteria.
- Archaea usually have multiple origins of DNA replication, unlike Bacteria which typically have one.
- Genetic studies show Archaea are more similar to Eukarya than to Bacteria in some respects.
Culturing and Examples
- Most Archaea cannot be easily cultured in labs due to unknown growth requirements.
- Genus Sulfolobus thrives in volcanic springs with high temperatures (~80°C) and acidity, resistant to hydrogen sulfide.
- Sulfolobus is studied for potential uses in treating and converting industrial waste.
Key Terms & Definitions
- Archaea — Domain of single-celled prokaryotes distinct from bacteria, often found in extreme environments.
- Prokaryote — Organism without a nucleus or membrane-bound organelles.
- Ether linkage — Chemical bond in Archaea membrane lipids, providing membrane stability.
- Ester linkage — Chemical bond found in Bacteria and Eukarya membranes.
- Peptidoglycan — Polymer in bacterial cell walls, absent in Archaea.
- Pseudopeptidoglycan — Similar structure to peptidoglycan, but chemically distinct, found in some Archaea.
Action Items / Next Steps
- Review further reading on differences in archaeal cell membrane chemistry.
- Consider potential biotechnological applications of extremophilic Archaea like Sulfolobus.