Module 2-Chapter 15

Bacteria, Archaea & Eukarya

Microbe

A microscopic, single-celled organism.

Human microbiome

The complete collection of microbes that live in and on our cells and bodies.

Citizen science

Research that is assisted by members of the public, who participate by collecting and sometimes analyzing data in cooperation with professional scientists.

Capsule

An additional protective layer that surrounds the cell wall in prokaryotes.

Pili (sing. pilus)

Short, hairlike projections that cover the surface of many bacteria and archaea.

Flagellum (pl. flagella)

A long, whiplike structure that assists some prokaryotes in locomotion.

Thermophile

A prokaryote, usually archaean, that can live in extremely hot environments, such as geysers, hot springs, and hydrothermal vents.

Halophile

A prokaryote, usually archaean, that can live in extremely salty environments.

Quorum sensing

A system of cell-to-cell communication used by prokaryotes that enables them to sense and respond to other bacteria in the area in accordance with the density of the population.

Binary fission

A type of cell division in which a cell simply divides into two equal halves, resulting in daughter cells that are genetically identical to each other and to the parent cell.

Sporulation

The formation of thick-walled dormant structures called spores.

Aerobes

Prokaryotes that need oxygen to survive.

Anaerobes

Prokaryotes that survive without oxygen.

Methanogen

An anaerobic archaean that feeds on hydrogen and produces methane gas as a by-product of its metabolism.

Fermentation

A metabolic pathway by which most anaerobic organisms extract energy from organic molecules. It begins with glycolysis and is followed by a special set of reactions whose only role is to help perpetuate glycolysis. Fermentation enables organisms to generate ATP anaerobically.

Heterotroph

A metabolic consumer, an organism that obtains energy by taking it from other sources. Chemoheterotrophs consume organic molecules as a source of energy and carbon. Photoheterotrophs absorb the energy of sunlight but require an organic source of carbon. Compare autotroph.

Autotroph

A metabolic producer, an organism that makes food on its own. Chemoautotrophs acquire their energy from inorganic chemicals in their environment. Photoautotrophs absorb the energy of sunlight and take in carbon dioxide to conduct photosynthesis. Compare heterotroph.

Chemoheterotroph

A type of heterotroph that derives both energy and carbon from organic molecules, such as carbohydrates, fats, and proteins. (See heterotroph.)

Photoheterotroph

An organism that obtains energy from sunlight while requiring organic compounds for carbon. (See
heterotroph.)

Photoautotroph

An organism that synthesizes its food using sunlight and carbon dioxide through photosynthesis. (See autotroph.)

Chemoautotroph

A type of autotroph that derives energy from the oxidation of inorganic molecules and uses carbon dioxide as a carbon source. (See autotroph.)

Nitrogen fixation

The process, carried out by bacteria, of taking nitrogen gas from the air and converting it to ammonia, making it available for plants.

Nutrient cycling

The process by which decomposers break down dead organisms or waste products, release the chemical elem-ents locked in the biological material, and return them to the environment.