Biology II - Chapter 24

Bacteria

One of the three domains of life, consisting of single-celled organisms without a nucleus

They have a cell wall made of peptidoglycan, typically have a single circular chromosome, and divide by binary fission

Plasmid

A small circular molecule of DNA carrying a small number of genes that replicates independently of the DNA in the bacterium's circular chromosome

not essential for the cell's survival, but it may contain genes that have adaptive value under specific environmental conditions

Peptidoglycan

complex polymer of sugars and amino acids that makes up the cell wall in bacteria

Horizontal gene transfer

The transfer of genetic material between organisms that are not parent and offspring

This process is a major source of genetic diversity in bacteria.

Conjugation

The direct cell-to-cell transfer of DNA, usually a plasmid

Genes that confer resistance to antibiotics are a well-studied example of horizontal gene transfer by this process

Transformation

DNA released to the environment by cell breakdown can be taken up by other cells

Biologists commonly use this in the laboratory to introduce genes into cells

Transduction

The transfer of DNA between cells by means of a virus

Widely used in the laboratory to introduce novel genes into bacteria for medical research

Archaea

One of the three domains of life, consisting of single-celled organisms with a single circular chromosome and lacking a membrane-bound nucleus

They divide by binary fission and differ from bacteria in many aspects of their cell and molecular biology

Carbon Cycle

the movement of carbon from the environment to organisms and back again

Cyanobacteria

the one group of bacteria that photosynthesizes much as plants and algae do

Aerobic

Utilizing oxygen

Anaerobic

Absence of oxygen

Fermentation

A process for extracting energy from fuel molecules that does not rely on oxygen or an electron transport chain but instead uses an organic molecule as an electron acceptor

Phototroph

An organism that captures energy from sunlight

Chemotroph

An organism that derives its energy directly from organic molecules such as glucose

Autotroph

An organism that is able to synthesize its own food using energy from sunlight or inorganic chemicals

Heterotroph

An organism that obtains its carbon from organic molecules synthesized by other organisms

Photoautotroph

An organism that uses light energy to make its own food from inorganic carbon sources like carbon dioxide (CO₂)

Photoheterotroph

An organism that uses the energy from sunlight to make ATP and relies on organic molecules obtained from the environment as the source of carbon for growth and other vital functions

Chemoautotroph

A microorganism, such as a bacterium, that obtains its carbon by the fixation of carbon dioxide, using energy derived from chemical reactions, not from sunlight

Chemoheterotroph

An organism that gets both its energy and carbon by consuming organic compounds made by other organisms

Primary Producer

An organism that takes up inorganic carbon, nitrogen, phosphorus, and other compounds from the environment and converts them into organic compounds
A source of food for heterotrophic organisms in the local environment

Assimilation

The process by which organisms incorporate nutrients obtained from the environment into more complex molecules

Nitrogen Fixation

The process by which some Bacteria and Archaea convert nitrogen gas (N2) into ammonia (NH3), a form biologically useful to primary producers

Nitrification

The process by which chemoautotrophic bacteria oxidize ammonia (NH3) to nitrite (NO2−) and then nitrate (NO3−)

Denitrification

The process in which some bacteria use nitrate as an electron acceptor in respiration, releasing N2 to the environment

Anammox

Anaerobic ammonia oxidation; energy metabolism found in some bacteria in which ammonium ions are oxidized by nitrite, yielding nitrogen gas as a by-product

Proteobacteria

The most diverse bacterial group, defined largely by similarities in rRNA gene sequences

It includes many of the organisms that populate the expanded carbon cycle and other biogeochemical cycles.

Gram-positive Bacteria

Bacteria that retain, in their thick peptidoglycan walls, the diagnostic dye originally developed by Hans Christian Gram

Gram-negative Bacteria

Bacteria with thin walls, which do not retain the dye, are said to be Gram negative

Endospore

A thick-walled, protective spore that forms inside a bacterial cell and resists extreme conditions such as heat, UV radiation, chemicals, and desiccation (drying out)

Hyperthermophile

An organism that requires an environment with high temperature

Methanogen

An archaeon that generates natural gas (methane, CH4) as a by-product of anaerobic energy metabolism

Stromatolite

A layered structure that records sediment accumulation by microbial communities

Coevolution

The process in which species evolve together, each responding to selective pressures imposed by the other