2 ­ Kingdoms Archaebacteria and Eubacteria (P5).notebook

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November 02, 2010

Characteristics

THE LIFE OF A PROKARYOTE• Prokaryotes are single-celled organisms. They are the smallest, simplest

organisms.• The group includes:

o Archaebacteria are found in anaerobic and extreme conditions (high [salt], high temperature, and low pH), similar to what are believed to be the conditions on the early Earth.§ Earth's early atmosphere did not contain oxygen, therefore the

earliest organisms were anaerobic.o Eubacteria includes the traditional bacteria and is the larger of the

two.• They are found in nearly every habitat

studied, including some that no other organism is able to withstand.

• Bacteria have a cell wall and cell membrane, but no membrane-bound organelles such as a nucleus, mitochondria, chloroplasts, Golgi apparatus, or ER. Some are covered by a layer of “slime” called a capsule.

Early Atmosphere

Primitive Earth

Early Atmosphere of Primitive Earth

• Probably H2 and He -Possibly lost to space because Earth's gravity is not strong enough to hold lighter gases

• Gases produced were probably similar to those created by modern volcanoes (H2O, CO2, SO2, CO, Cl2, N2, H2) and NH3 and CH4.

-No free O2 at this time (not found in volcanic gases). Back

Shapes Cilia and Flagella

• Some bacteria are able to move using special cell structures called cilia and flagella.o Hair-like cilia (singular, cilium) and tail-like flagella (singular,

flagellum) are projections from the cell.o By repetitive beating (like a bending motion), they cause the cell to

move. Think of oars in a boat. Flagella can propel the cell by waving back and forth.§ If a cell is fixed in place, they can also cause water to move

across the surface..

Resp/Nutr

RESPIRATION• Obligate aerobes must have oxygen.• Obligate anaerobes can not survive in the presence of oxygen.• Facultative anaerobes will use oxygen if it is present but do not need it.

NUTRITION• Most are heterotrophic…

o Some are parasites which live off a living host.o Some are decomposers, feeding on dead organisms and waste.

• Some are autotrophic… o Either use chemicals as a source of energy (chemoautotrophs) or are

photosynthetic (photoautotrophs).

Early symptomatic HIV infection: Mycobacterium marinum infection on the hand  Bacterial Pericarditis

Reproduction

REPRODUCTION• Prokaryotes have a single circular chromosome attached to the inside of the

plasma membrane.• Asexual reproduction

o Prokaryotes reproduce by simply splitting in two in a process called binary fission.

o The DNA is copied and the cell divides into two identical cells.• Sexual reproduction

o Sexual reproduction combines genes from two different individuals and increases variation. Prokaryotes do not technically reproduce sexually but can mix genes with one another.

o Conjugation - Two cells join briefly and one cell donates some DNA (called a plasmid) to the other one. Sometimes part of the cell‛s chromosome is donated as well.

o Transformation - Bacteria can also pick up pieces of DNA from the environment.

o Transduction - Sometimes viruses transfer pieces of DNA from one cell to another.

• Endosporeso Some bacteria form endospores when environmental conditions become

unfavorable.o Endospores are DNA and a small amount of cytoplasm enclosed in a

tough cell wall. They are resistant to extremes in temperature, drying, and harsh chemicals.

• Mutation is a large source of genetic diversity in bacteria.

Single Chromosome

Conjugation

Endospores

Binary Fission

2 ­ Kingdoms Archaebacteria and Eubacteria (P5).notebook

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November 02, 2010

Chromosome

E. coli

Reproduction

Cell Phones The Eyes of Nye (Antibiotics)

The Eyes of Nye (Antibiotics)