Transcript Bacteria and Viruses

Bacteria and Viruses
Bacteria
• Prokaryotes are the oldest living things on
Earth.
• Prokaryotes are single-celled organisms that
do not have membrane-bound organelles.
• Prokaryotes are divided into two major
groups:
– Domain Archaea
– Domain Bacteria
Archaea
• Found in many places
• Structurally very different from bacteria
Bacteria
• Most known prokaryotes are members of
this domain
• One square inch of skin is host to over
100,000 bacteria!
Bacterial Structure
- no membrane-bound organelles, but do have
many internal structures
- Have genetic material in the form of DNA
- Often have small extra loops of DNA called
plasmids.
- Have ribosomes
Obtaining Energy and Nutrients
• Bacteria differ in how they obtain energy
and nutrients
• Grouping prokaryotes based on their energy
source separates them into
photoautotrophs, chemoautotrophs, and
heterotrophs.
Photoautotrophs
• Get their energy from sunlight through
photosynthesis
• Includes purple sulfur and nonsulfer
bacteria, green sulfur bacteria, and
cyanobacteria.
• Cyanobacteria are a major component of the
plankton that floats in the ocean.
Chemoautotrophs
• The only organisms that can get their energy
from inorganic sources.
• They use molecules that contain sulfur or
nitrogen and simple organic molecules to
obtain energy.
Heterotrophs
• Most prokaryotes are heterotrophs and get
both their energy and their nutrients from
other organisms.
• Most absorb their nutrients from dead
organisms, but some are parasites or
pathogens.
Reproduction and Adaptation
• Prokaryotes reproduce by binary fission;
exchange genetic material through
conjugation, transformation, and
transduction; and survive harsh conditions
by forming endospores.
Binary Fission
• Prokaryotes usually reproduce asexually by
binary fission.
• A single cell divides into two identical new
cells.
• Mutations do occur during prokaryotic
reproduction, and new forms emerge
frequently.
Genetic Recombination
• There are 3 ways in which prokaryotes can
form new genetic combinations.
– Conjugation- two bacteria exchange genetic
material.
– Transformation- bacteria take up DNA
fragments from their environment.
– Transduction- genetic material is transferred
by a virus.
Endospore formation
• Endospore = thick-walled structures formed
by bacteria to survive harsh conditions.
• Can survive boiling, radiation, and acid.
• Show no signs of life and can be revived
after hundreds of years.