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

• 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

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.
María Paula Vélez R

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

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

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.
María Paula Vélez R

Gram-positive
Simpler and have more
Peptidoglycan.
Gram negative complex cell wall and small amount of peptidoglycan.
María Paula Vélez R

María Paula Vélez R

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

María Paula Vélez R

María Paula Vélez R

Investigate:
1. Two diseases caused by bacterias.
2. What are antbiotics.
María Paula Vélez R