Chapter 26: Bacteria and Archaea: the Prokaryotic Domains CHAPTER 26 Bacteria and Archaea: The Prokaryotic Domains

Chapter 26: Bacteria and Archaea: the Prokaryotic Domains

CHAPTER 26Bacteria and Archaea:

The Prokaryotic Domains


Chapter 26: Bacteria and Archaea: the Prokaryotic DomainsWhy Three Domains?Why Three Domains?

General Biology of the ProkaryotesGeneral Biology of the Prokaryotes

Prokaryotes in Their EnvironmentsProkaryotes in Their Environments


Prokaryote Phylogeny and DiversityProkaryote Phylogeny and Diversity

The BacteriaThe Bacteria

The The ArchaeaArchaea



Why Three Domains?

• Living organisms can be divided into Living organisms can be divided into three domains: Bacteria, Archaea, and three domains: Bacteria, Archaea, and Eukarya. Eukarya.

• The prokaryotic Archaea and Bacteria The prokaryotic Archaea and Bacteria differ from each other more radically differ from each other more radically than the Archaea from the Eukarya.than the Archaea from the Eukarya.

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Why Three Domains?

• Evolutionary relationships of the Evolutionary relationships of the domains were revealed by rRNA domains were revealed by rRNA sequences. sequences.

• Their common ancestor lived more Their common ancestor lived more than 3 billion years ago, that of the than 3 billion years ago, that of the Archaea and Eukarya at least 2 billion Archaea and Eukarya at least 2 billion years ago. years ago.

Review Figure Review Figure 26.226.2 and Table and Table 26.126.1

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Figure 26.2

Figure 26.2Figure 26.2

figure 26-02.jpg


Table 26.1

Table 26.1Table 26.1

table 26-01.jpg


General Biology of the Prokaryotes

• The prokaryotes are the most The prokaryotes are the most numerous organisms on numerous organisms on Earth,occupying an enormous variety Earth,occupying an enormous variety of habitats.of habitats.

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• Most prokaryotes are cocci, bacilli, or Most prokaryotes are cocci, bacilli, or spiral forms. Some link together to spiral forms. Some link together to form associations, but very few are form associations, but very few are truly multicellular.truly multicellular.

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• Prokaryotes lack nuclei, membrane-Prokaryotes lack nuclei, membrane-enclosed organelles, and cytoskeletons. enclosed organelles, and cytoskeletons.

• Their chromosomes are circular. Their chromosomes are circular.

• They often contain plasmids. They often contain plasmids.

• Some contain internal membrane Some contain internal membrane systems.systems.

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• Many prokaryotes move by means of Many prokaryotes move by means of flagella, gas vesicles, or gliding flagella, gas vesicles, or gliding mechanisms. mechanisms.

• Prokaryotic flagella rotate.Prokaryotic flagella rotate.

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• Prokaryotic cell walls differ from those Prokaryotic cell walls differ from those of eukaryotes. of eukaryotes.

• Bacterial cell walls generally contain Bacterial cell walls generally contain peptidoglycan. peptidoglycan.

• Differences in peptidoglycan content Differences in peptidoglycan content result in different reactions to the Gram result in different reactions to the Gram stain. stain.

Review Figure Review Figure 26.726.71212


Figure 26.7


figure 26-07.jpg



• Prokaryotes reproduce asexually by Prokaryotes reproduce asexually by fission, but also exchange genetic fission, but also exchange genetic information.information.

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General Biology of the Prokaryotes • Prokaryotes’ metabolic pathways and Prokaryotes’ metabolic pathways and

nutritional modes include obligate and nutritional modes include obligate and facultative anaerobes, and obligate facultative anaerobes, and obligate aerobes. aerobes.

• Nutritional types include Nutritional types include photoautotrophs, photoheterotrophs, photoautotrophs, photoheterotrophs, chemoautotrophs, and chemoautotrophs, and chemoheterotrophs. chemoheterotrophs.

• Some base energy metabolism on Some base energy metabolism on nitrogen- or sulfur-containing ions. nitrogen- or sulfur-containing ions.

Review Figure Review Figure 26.826.8 and Table and Table 26.226.2

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Figure 26.8


figure 26-08.jpg


Table 26.2

Table 26.2Table 26.2

table 26-02.jpg


Prokaryotes in Their Environments

• Some prokaryotes play key roles in Some prokaryotes play key roles in global nitrogen and sulfur cycles.global nitrogen and sulfur cycles.

• Nitrogen fixers, nitrifiers, and Nitrogen fixers, nitrifiers, and denitrifiers do so in the nitrogen cycle. denitrifiers do so in the nitrogen cycle.


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Figure 26.10


figure 26-10.jpg



• Photosynthesis by cyanobacteria Photosynthesis by cyanobacteria generated the oxygen gas that generated the oxygen gas that permitted the evolution of aerobic permitted the evolution of aerobic respiration and the appearance of respiration and the appearance of present-day eukaryotes.present-day eukaryotes.

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• Many prokaryotes live in or on other Many prokaryotes live in or on other organisms, with neutral, beneficial, or organisms, with neutral, beneficial, or harmful effects.harmful effects.

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• A minority of bacteria are pathogens. A minority of bacteria are pathogens. Some produce endotoxins, which are Some produce endotoxins, which are rarely fatal; others produce often rarely fatal; others produce often highly toxic exotoxins.highly toxic exotoxins.

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Prokaryote Phylogeny and Diversity

• Phylogenetic classification of Phylogenetic classification of prokaryotes is based on rRNA prokaryotes is based on rRNA sequences and other molecular sequences and other molecular evidence.evidence.

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• Lateral gene transfer among Lateral gene transfer among prokaryotes makes it difficult to infer prokaryotes makes it difficult to infer prokaryote phylogeny. prokaryote phylogeny.

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• Evolution can proceed rapidly in Evolution can proceed rapidly in prokaryotes because they are haploid prokaryotes because they are haploid and can multiply rapidly.and can multiply rapidly.

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The Bacteria

• There are far more known bacteria There are far more known bacteria than archaea. than archaea.

• One phylogenetic classification of the One phylogenetic classification of the domain Bacteria groups them into over domain Bacteria groups them into over a dozen groups.a dozen groups.

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The Bacteria

• The most ancient bacteria, like the The most ancient bacteria, like the most ancient archaea, may be most ancient archaea, may be thermophiles, suggesting that life thermophiles, suggesting that life originated in a hot environment.originated in a hot environment.

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The Bacteria

• All four nutritional types occur in the All four nutritional types occur in the Proteobacteria. Proteobacteria.

• Metabolism in different proteobacteria Metabolism in different proteobacteria groups has evolved along different groups has evolved along different lines. lines.


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Figure 26.12


figure 26-12.jpg


The Bacteria

• Cyanobacteria, unlike other bacteria, Cyanobacteria, unlike other bacteria, photosynthesize using the same photosynthesize using the same pathways plants use. pathways plants use.

• Many fix nitrogen.Many fix nitrogen.

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The Bacteria

• Spirochetes move by means of axial Spirochetes move by means of axial filaments.filaments.

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The Bacteria

• Chlamydias are tiny parasites that live Chlamydias are tiny parasites that live within the cells of other organisms.within the cells of other organisms.

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The Bacteria

• Firmicutes are diverse; some produce Firmicutes are diverse; some produce endospores, resting structures endospores, resting structures resistant to harsh conditions. resistant to harsh conditions.

• Some actinomycetes produce Some actinomycetes produce important antibiotics. important antibiotics.

• Actinomycetes grow as branching Actinomycetes grow as branching filaments.filaments.

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The Bacteria

• Mycoplasmas, the tiniest living things, Mycoplasmas, the tiniest living things, lack conventional cell walls and have lack conventional cell walls and have very small genomes.very small genomes.

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The Archaea

• Archaea cell walls lack peptidoglycan, Archaea cell walls lack peptidoglycan, and their membrane lipids contain and their membrane lipids contain branched long-chain hydrocarbons branched long-chain hydrocarbons connected to glycerol by ether connected to glycerol by ether linkages. linkages.


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Figure 26.22


figure 26-22.jpg


The Archaea

• The domain Archaea can be divided The domain Archaea can be divided into two kingdoms: into two kingdoms: Crenarchaeota Crenarchaeota Euryarchaeota.Euryarchaeota.

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The Archaea

• Crenarchaeota are heat-loving and Crenarchaeota are heat-loving and often acid-loving archaea.often acid-loving archaea.

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The Archaea

• Methanogens produce methane by Methanogens produce methane by reducing carbon dioxide. reducing carbon dioxide.

• Some live in the guts of herbivorous Some live in the guts of herbivorous animals; some in high-temperature animals; some in high-temperature environments on the ocean floor.environments on the ocean floor.

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The Archaea

• Extreme halophiles are salt lovers that Extreme halophiles are salt lovers that lend a pinkish color to salty lend a pinkish color to salty environments; some grow in extremely environments; some grow in extremely alkaline environments.alkaline environments.

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The Archaea

• Archaea of the genus Thermoplasma Archaea of the genus Thermoplasma lack cell walls, are thermophilic and lack cell walls, are thermophilic and acidophilic, and have a tiny genome acidophilic, and have a tiny genome (1,100,000 base pairs).(1,100,000 base pairs).

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Chapter 26: Bacteria and Archaea: the Prokaryotic Domains CHAPTER 26 Bacteria and Archaea: The Prokaryotic Domains