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PROKARYOTES
María Paula Vélez R
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.
María Paula Vélez R
Prokaryotes are single-celled organisms that do
not have a membrane-bound nucleus.
María Paula Vélez R
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.
María Paula Vélez R
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.
María Paula Vélez R
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-positive
Simpler and have more
Peptidoglycan.
Gram negative
complex 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.
María Paula Vélez R