Anaerobic Respiration
A catabolic pathway in which inorganic molecules other than oxygen accept electrons at the “downhill” end of electron transport chains.
Bioremediation
The use of organisms to detoxify and restore polluted and degraded ecosystems.
Commensalism
A symbiotic relationship in which one organism benefits but the other is neither helped nor harmed.
Decomposer
An organism that absorbs nutrients from nonliving organic material such as corpses, fallen plant material, and the wastes of living organisms and converts them to inorganic forms; a detritivore.
Endospore
A thick-coated, resistant cell produced by some bacterial cells when they are exposed to harsh conditions.
Endotoxin
A toxic component of the outer membrane of certain gram-negative bacteria that is released only when the bacteria die.
Exotoxin
A toxic protein that is secreted by a prokaryote or other pathogen and that produces specific symptoms, even if the pathogen is no longer present.
Extreme Halophiles
An organism that lives in a highly saline environment, such as the Great Salt Lake or the Dead Sea.
Extreme Thermophiles
An organism that tribes in hot environments (60-80ºC or hotter).
Extremophile
An organism that lives in environmental conditions so extreme that few other species can survive there. Extremophiles include extreme halophiles (“salt lovers”) and extreme thermophiles (“heat lovers”).
Facultative Anaerobe
An organism that makes ATP by aerobic respiration if oxygen is present but that switches to anaerobic respiration or fermentation if oxygen is not present.
Gram-Negative
Describing the group of bacteria that have a cell wall that is structurally more complex and contains less peptidoglycan than the cell wall of gram-positive bacteria. Gram-negative bacteria are often more toxic than gram-positive bacteria.
Gram-Postive
Describing the group of bacteria that have a cell wall that is structurally less complex and contains more peptidoglycan than the cell wall of gram-negative bacteria. Gram-positive bacteria are usually less toxic than gram-negative bacteria.
Gram Stain
A staining method that distinguishes between two different kinds of bacterial cel walls; may be used to determine medical response to an infection.
Host
The larger participant in a symbiotic relationship, often providing a home and food source for the smaller symbiont.
Mutualism
A symbiotic relationship in which both participants benefit.
Nitrogen Fixation
The conversion of atmospheric nitrogen (N2) to ammonia (NH3). Biological nitrogen fixation is carried out by certain prokaryotes, some of which have mutualistic relationships with plants.
Obligate Anaerobe
An organism that only carries out fermentation or anaerobic respiration. Such organisms cannot use oxygen and in fact may be poisoned by it.
Plasmid
A small, circular, double-stranded DNA molecule that carries accessory genes separate from those of a bacterial chromosome; In DNA cloning, used as vector carrying up to 10,000 base pairs (10 kB) of DNA. Plasmids are also found in some eukaryotes, such as yeasts.
R-Plasmids
A bacterial plasmid carrying genes that confer resistance to certain antibiotics.
Symbiosis
An ecological relationship between organisms of 2 different species that live together in direct and intimate contact.
Transformation
A change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, transformation results in horizontal gene transfer.