19.1 Bacteria

Prokaryotes

• Unicellular organism lacking a nucleus.

Bacillus

• Rod-shaped prokaryote.

Coccus

• Spherical prokaryote.

Spirillum

• Spiral or corkscrew-shaped prokaryote.

Chemoheterotroph

• Organism that must take in organic molecules for both energy and carbon.

Photoheterotroph

• Organism that is photosynthetic but needs organic compounds as a carbon source.

Photoautotroph

• Organism that uses energy from sunlight to convert carbon dioxide and water to carbon compounds.

Chemoautotroph

• Organism that makes organic carbon molecules from carbon dioxide using energy from chemical reactions.

Obligate Aerobe

• Organism that requires a constant supply of oxygen in order to live.

Obligate Anaerobe

• Organism that cannot live in the presence of oxygen.

Facultative Anaerobe

• Organism that can survive with or without oxygen.

Binary Fission

• Type of asexual reproduction in which an organism replicates its DNA and divides in half, producing two identical daughter cells.

Conjugation

• Form of sexual reproduction in which paramecia and some prokaryotes exchange genetic information.

Endospore

• Type of spore formed when a bacterium produces a thick internal wall that encloses its DNA and a portion of its cytoplasm.

Nitrogen Fixation

• Process of converting nitrogen gas into ammonia.

Key Concept

• Bacteria are vital to maintaining the living world. Some are producers that capture energy by photosynthesis. Other are decomposers that break down the nutrients in dead matter and the atmosphere.