Chapter 4
Prokaryotic Diversity
Figure 4.1 The bacteriumShewanellalives in the deep sea, where there is little oxygen diffused in the water. It is
able to survive in this harsh environment by attaching to the sea floor and using long appendages, called
“nanocables,” to sense oxygen. (credit b: modification of work by Liza Gross)
Chapter Outline
4.1 Prokaryote Habitats, Relationships, and Microbiomes
4.2 Proteobacteria
4.3 Nonproteobacteria Gram-Negative Bacteria and Phototrophic Bacteria
4.4 Gram-Positive Bacteria
4.5 Deeply Branching Bacteria
4.6 ArchaeaIntroduction
Scientists have studied prokaryotes for centuries, but it wasn’t until 1966 that scientist Thomas Brock (1926–)
discovered that certain bacteria can live in boiling water. This led many to wonder whether prokaryotes may also live
in other extreme environments, such as at the bottom of the ocean, at high altitudes, or inside volcanoes, or even on
other planets.
Prokaryotes have an important role in changing, shaping, and sustaining the entire biosphere. They can produce
proteins and other substances used by molecular biologists in basic research and in medicine and industry. For
example, the bacteriumShewanellalives in the deep sea, where oxygen is scarce. It grows long appendages, which
have special sensors used to seek the limited oxygen in its environment. It can also digest toxic waste and generate
electricity.Other species ofprokaryotes canproducemoreoxygenthantheentire Amazon rainforest, while still others
supply plants, animals, and humans with usable forms of nitrogen; and inhabit our body, protecting us from harmful
microorganisms and producing some vitally important substances. This chapter will examine the diversity, structure,
and function of prokaryotes.
Chapter 4 | Prokaryotic Diversity 139