Summary Bacteria and Archaea Chapter notes

**Bacteria:** *Bacterial Life:* - Bacteria are single-celled microorganisms that belong to the domain Bacteria. - They are some of the most ancient life forms on Earth, with fossils dating back over 3.5 billion years. - Bacteria are incredibly diverse and are found in virtually every habitat on Earth, from the deepest oceans to the hottest deserts and even inside the human body. *Types of Bacteria:* 1. **Shape-based Classification:** - Cocci: Spherical bacteria (e.g., Streptococcus). - Bacilli: Rod-shaped bacteria (e.g., Escherichia coli). - Spirilla: Spiral-shaped bacteria (e.g., Spirochaetes). 2. **Classification by Respiration:** - Aerobic: Require oxygen for respiration. - Anaerobic: Can live without oxygen. 3. **Nutritional Classification:** - Autotrophs: Produce their own food through photosynthesis or chemosynthesis. - Heterotrophs: Depend on other organisms for nutrients. 4. **Gram Staining:** - Gram-positive: Retain the violet stain (e.g., Staphylococcus). - Gram-negative: Do not retain the violet stain (e.g., Escherichia coli). *Bacterial Habitats:* - Bacteria can be found in a wide range of environments, including soil, water, the human gut, and extreme environments like hydrothermal vents, acid mines, and polar ice caps. - Some bacteria form symbiotic relationships with other organisms, such as nitrogen-fixing bacteria in plant roots. **Archaea:** *Archaeal Life:* - Archaea are single-celled microorganisms that belong to the domain Archaea, a group distinct from bacteria and more closely related to eukaryotes. - They were initially mistaken for bacteria but have fundamental genetic and biochemical differences. *Types of Archaea:* 1. **Methanogens:** - Found in anaerobic environments, such as swamps and the digestive tracts of animals. - Produce methane as a metabolic byproduct. 2. **Halophiles:** - Thrive in high-salt environments like salt flats and hypersaline lakes. 3. **Thermophiles:** - Flourish in extreme heat, like hot springs and deep-sea hydrothermal vents. *Archaeal Habitats:* - Archaea are known for their ability to thrive in extreme environments, where most other organisms cannot survive. - Some archaea, such as extremophiles, are found in places with extreme temperature, salinity, or acidity, while others inhabit more common environments like the human gut. In summary, bacteria and archaea are two distinct domains of microorganisms that exhibit remarkable diversity in terms of morphology, metabolism, and habitat preferences. Bacteria are ubiquitous, found in a wide range of environments and can be classified in various ways, including by shape, respiration, and staining. Archaea, on the other hand, are known for their ability to thrive in extreme conditions and include methanogens, halophiles, and thermophiles among their diverse groups. Both bacteria and archaea play essential roles in various ecosystems and have significant implications for human health and biotechnology.