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PROKARYOTES

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Prokaryotes are the most numerous organisms

on earth. They are found almost everywhere,

from the skin of a fingertip to the waters of a

thermal geyser to the freezing landscape of the

Artic.The earliest fossils of prokaryotes indicate

that they lived before other forms of life evolved.

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Prokaryotes are single-celled organisms that do not have a membrane-bound nucleus.

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María Paula Vélez R

Archaebacteria

• Archae are not like bacterias in many ways. For example, their cell walls do not have peptidoglycan (protein found in bacterias cell wall).

• Archae were first discovered in extreme environments such as swamps, salt lakes and hot springs.

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Archeal groups:1. Methanogens: Convert hydrogen gas and

carbon dioxide into methane gas. Oxygen is poisonous for them, so they can live only in places that lack oxygen.

Example: methanogens that live in the intestinal tract of the cow.

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2. Halophiles: “salt-loving” archae that live in environments that have very high salt concentration such as the Dead sea.

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3. Thermoacidodophiles: live in very acid environments that have also very high temperatures. Some can live up to 110°C and at a ph less than 2 (strong acid). They can live near volcanic vents or hydrothermal vents.

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Eubacteria

Most known prokaryotes are eubacteria. They occur in many shapes and sizes and have different genetic characteristics.

There are three main ways to classify them:- By cell wall- By shape- By biochemical properties and evolutionary

relations.

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Cell wall:

Gram-positiveSimpler and have more Peptidoglycan.

Gram negativecomplex cell wall and small amount of peptidoglycan.

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Shape:

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Biochemical properties and evolutionary relations:

- Proteobacteria (most are symbiotic)- Gram positive (most cause diseases)- Cyanobacteria (photosynthetic bacterias)- Spirochetes (gram-negative)- Chlamydia (gram-negative cocci)

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HELPFUL BACTERIA

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HARMFUL BACTERIA

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Homework

Investigate:

1. Two diseases caused by bacterias.2. What are antbiotics.