Bacteria and Archaea

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Korarcheotes

Euryarchaeotes

Crenarchaeotes

Nanoarchaeotes

Proteobacteria

Chlamydias

Spirochetes

Cyanobacteria

Gram-positive

bacteria

Domain

Eukarya

Domain Archaea

Domain Bacteria

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Domain: Archaea

Archaea are prokaryotes and share certain traits with bacteria and other traits with eukaryotes.

Some archaea live in extreme environments and are called extremophiles.

Extreme halophiles live in highly saline, salty environments.

Extreme thermophiles thrive in very hot environments.

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Archaea appear to be more closely related to Eukarya than to Bacteria

Eukarya

Archaea

Bacteria

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Extreme Thermophiles

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Methanogens live in swamps and marshes and produce methane as a waste product.

Methanogens are strict anaerobes and are poisoned by O2

In recent years, genetic prospecting has revealed many new groups of archaea.

Some of these may offer clues to the early evolution of life on Earth.

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Bacteria

Bacteria include the vast majority of prokaryotes of which most people are aware.

Diverse nutritional types are scattered among the major groups of bacteria.

Rhizobium are nitrogen fixing bacteria. They form root nodules in legumes (mutualism ++ ) and fix atmospheric N2

Agrobacterium produces tumors in plants and is used in genetic engineering.

Escherichia coli resides in the intestines of many mammals and is not normally pathogenic.

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Common Bacteria

Chlamydias are parasitic bacteria that live within animal cells.

Chlamydia trachomatis causes blindness and nongonococcal urethritis by sexual transmission.

Spirochetes are helical heterotrophs.

Some, such as Treponema pallidum, which causes syphilis, and Borrelia burgdorferi, which causes Lyme disease, are parasites.

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Major Groups of Bacteria

CHLAMYDIAS

2.5 µm

CYANOBACTERIA

SPIROCHETES

GRAM-POSITIVE BACTERIA

Chlamydia (arrows) inside an

animal cell (colorized TEM)

Leptospira, a spirochete

(colorized TEM)

5 µm

50 µm

Two species of Oscillatoria,

filamentous cyanobacteria (LM)

Streptomyces, the source of