CHAPTER 18 Summary

• Prokaryotes are unicellular organisms that lack internal organelles and whose DNA is not contained in a nucleus.
• Prokaryotes are found in virtually every environment on Earth, even those with seemingly inhospitable conditions, such as hydrothermal vents on the ocean floor.
• Genetic analysis has led to the categorization of life into three domains: Bacteria, Archaea, and Eukarya. Each domain of life has a distinct evolutionary history.
• Both bacteria and archaea have prokaryotic cells, but they otherwise differ in their structure, biochemistry, and lifestyles.
• Bacteria are a diverse group of prokaryotic organisms with many unique adaptations such as flagella and capsules that allow them to live and thrive in many environments.
• Some bacteria are disease-causing pathogens, but most are harmless and even beneficial. Cyanobacteria, for example, are responsible for much of the photosynthesis that supports life on Earth.
• Often known as “extremophiles,” archaea live in some of the most inhospitable conditions on Earth, such as hydrothermal vents. Many archaea flourish in less extreme environments as well.
• The harsh conditions of Lost City may resemble the conditions of the early Earth. The prokaryotic inhabitants of Lost City may be metabolically similar to the earliest known life.
• The energy that fuels life in Lost City comes from a geological source, rather than from sunlight, making Lost City one of the few communities on Earth that is not powered by photosynthesis.

• MORE TO EXPLORE

  • Lost City Home http://www.lostcity.washington.edu/
  • Brazelton, W. J., et al. (2011) Physiological differentiation within a single-species biofilm fueled by serpentinization. mBio 2(4): e00127–11.
  • Brazelton, W. J., et al. (2006) methane- and sulfur-metabolizing microbial communities dominate the Lost City hydrothermal field ecosystem. Applied and Environmental Microbiology 72(9):6257–6270.
  • Kelley, D. S. (2005) From the mantle to microbes: the Lost City hydrothermal field. Oceanography 18(3):32-45. http://www.tos.org/oceanography/archive/18-3_kelley.pdf
  • Exploring Life’s Origins http://exploringorigins.org