Chapter 15: Bacteria and Archaea

A comprehensive vocabulary review of key concepts, definitions, structural components, metabolic types, and processes related to Chapter 15: Bacteria and Archaea.

Microbes

Microscopic organisms, primarily bacteria.

Human Microbiome

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

Stromatolites

Structures in rocks with particular patterns indicative of bacterial activity and possibly the remains of early life, the oldest of which suggest bacteria existed 3.7 billion years ago (bya).

Prokaryotes

Single-celled organisms that include both Bacteria and Archaea, which have a single loop of DNA, are much smaller than eukaryotic cells, lack membrane-enclosed organelles, and are capable of rapid reproduction.

Citizen Science

Research projects in which the public plays a part in cooperation with professional scientists by contributing, collecting, or analyzing data.

Bacillus

A rod-shaped bacterial or archaeal cell.

Coccus

A sphere-shaped bacterial or archaeal cell.

Spirillum

A spiral-shaped bacterial or archaeal cell.

Spirochete

A corkscrew-shaped bacterial or archaeal cell.

Vibrio

A comma-shaped bacterial or archaeal cell.

Cell Wall (Prokaryotic)

A protective layer surrounding the plasma membrane found in most bacteria and many archaeans.

Capsule

A layer around the cell wall of some bacteria that helps disease-causing bacteria evade the host's immune system.

Pili

Short, hairlike structures present on many bacteria and archaeans used to link together or attach to surfaces.

Flagellum

A long, whiplike structure found on some bacteria and archaeans that functions to propel the cell through liquid.

Thermophiles

Organisms (often archaeans) adapted to survive in extremely high-temperature environments ("heat lovers").

Halophiles

Organisms (often archaeans) adapted to live in highly saline environments ("salt lovers").

Quorum Sensing

A system of cell-to-cell communication that enables bacteria (and archaea) to sense and respond to other bacteria in the area based on population density.

Biofilms

Tough aggregates formed by bacteria of the same or different species coordinating their behavior via quorum sensing.

Binary Fission

A form of asexual reproduction in prokaryotes where the parent cell's DNA is copied and one copy is transferred into each of the resulting daughter cells.

Horizontal Gene Transfer

The process by which microbes capture bits of DNA from their environment or other bacteria and incorporate them into their own genetic material.

Bacterial Conjugation

A mechanism of horizontal gene transfer where a bacterium directly trades DNA with another bacterium.

Sporulation

The formation of thick-walled dormant structures called spores by some types of bacteria (but no archaeans) to survive extreme conditions like boiling, freezing, or antibiotics.

Aerobes

Organisms that require oxygen to survive.

Anaerobes

Organisms that do not use oxygen and can survive without it.

Methanogens

Anaerobic organisms that feed on hydrogen and produce methane gas.

Chemoheterotrophs

Heterotrophic organisms that consume organic molecules to obtain both energy and carbon.

Photoheterotrophs

Heterotrophic organisms that acquire carbon from organic sources but derive their energy from sunlight.

Chemoautotrophs

Autotrophic organisms that acquire carbon from carbon dioxide and energy from inorganic chemicals in their environment.

Photoautotrophs

Autotrophic organisms that absorb energy from sunlight and use carbon dioxide to perform photosynthesis.

Cyanobacteria

A group of aquatic photoautotrophic bacteria that evolved photosynthesis and released oxygen gas as a by-product, facilitating the oxygenation of Earth's atmosphere.

Nitrogen Fixation

The process by which certain bacteria convert nitrogen gas from the atmosphere into ammonia.

Decomposers

Consumers that extract nutrients from the remains of dead or dying organisms and waste products, returning chemical elements to the environment.

Nutrient Cycling

The breakdown of dead or dying biological material or waste products by decomposers, which releases locked chemical elements back into the environment for use by autotrophs and heterotrophs.

Dysbiosis

A state in which the human microbiome shifts out of balance, potentially causing illness.