Title: Archaea | Microbiology
Headings: Archaea
Archaea
Learning Objectives
Crenarchaeota
Think about It
Euryarchaeota
Think about It
Finding a Link Between Archaea and Disease
Key Concepts and Summary
Multiple Choice
Fill in the Blank
Think about It

Content: presented evidence that an archaean called Methanobrevibacter oralis inhabits the gums of patients with periodontal disease. The authors suggested that the activity of these methanogens causes the disease. [ 6] However, it was subsequently shown that there was no causal relationship between M. oralis and periodontitis. It seems more likely that periodontal disease causes an enlargement of anaerobic regions in the mouth that are subsequently populated by M. oralis. [ 7]
There remains no good answer as to why archaea do not seem to be pathogenic, but scientists continue to speculate and hope to find the answer. Key Concepts and Summary
Archaea are unicellular, prokaryotic microorganisms that differ from bacteria in their genetics, biochemistry, and ecology. Some archaea are extremophiles, living in environments with extremely high or low temperatures, or extreme salinity. Only archaea are known to produce methane. Methane-producing archaea are called methanogens. Halophilic archaea prefer a concentration of salt close to saturation and perform photosynthesis using bacteriorhodopsin.