Bacteria and Archaea The Prokaryotic Domains

The ancient Phoenicians called it the "river of fire." Today, Spanish astro-biologist Ricardo Amils Pibernat calls Spain's Río Tinto a possible model for the scene of the origin of the life that may have existed on Mars. The river wends its way through a huge deposit of iron pyrite—"fool's gold," or iron disulfide. Prokaryotes in the river and in the damp, acidic soil from which it arises convert the pyrite into sulfuric acid and dissolved iron. The iron gives the river its brilliant red color.

Over a period of at least 300,000 years, these prokaryotes have produced an environment seemingly hostile to life. The Río Tinto has a pH of 2 and exceptionally high concentrations of heavy metals, especially iron. The concentrations of oxygen in the river and in its source soil are extremely low. It is that soil that Amils believes resembles the kind of environment in which life could have begun on Mars. Whatever the truth of that speculation, the Río Tinto represents one of the most unusual habitats for life on Earth.

The organisms most commonly found in such extremely acidic environments belong to the two major groups of prokaryotes: Bacteria and Archaea. The bacteria live in almost every environment on Earth. The archaea are a superficially similar group of microscopic, unicellular prokaryotes. However, both the biochemistry and the genetics of bacteria differ in numerous ways from those of archaea. Not until the 1970s did biologists discover how radically different bacteria and archaea really are. And only with the sequencing of an archaeal genome in 1996 did we realize just how extensively archaea differ from both bacteria and eukaryotes.

Many biologists acknowledge the antiquity of these clades and the importance of their differences by recognizing three domains of living things: Bacteria, Archaea, and Eukarya. The domain Bacteria comprises the "true bacteria." The domain Archaea (Greek archaios, "ancient") comprises other prokaryotes once called (inaccurately) "ancient bacteria." The domain Eukarya includes all other living things on Earth.

Dividing the living world in this way, with two prokaryotic domains and a single domain for all the

Earth or Ancient Mars? Spain's Rfo Tinto owes its rich red color—and its extreme acidity—to the action of prokaryotes on iron pyrite-rich soil.

Earth or Ancient Mars? Spain's Rfo Tinto owes its rich red color—and its extreme acidity—to the action of prokaryotes on iron pyrite-rich soil.

Bacteria And Archaea Differ What Way

eukaryotes, fits with the current trend toward reflecting evolutionary relationships in classification systems. In the eight chapters of Part Five, we celebrate and describe the diversity of the living world—the products of evolution. This chapter focuses on the two prokaryotic domains. Chapters 28-34 deal with the protists and the kingdoms Plantae, Fungi, and Animalia.

In this chapter, we pay close attention to the ways in which the two domains of prokaryotic organisms resemble each other as well as the ways in which they differ. We will describe the impediments to the resolution of evolutionary relationships among the prokaryotes. Then we will survey the surprising diversity of organisms within each of the two domains, relating the characteristics of the different prokaryotic groups to their roles in the biosphere and in our lives.

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  • frank
    What r 2 ways true bacteria are different from archae?
    8 years ago

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