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anaerobic respiration

a catabolic pathway in which inorganic molecules other than

oxygen accept electrons at the “downhill” end of electron transport chains.

biofilm

A surface

in metabolic cooperation.

capsule

1. In many prokaryotes, a dense and well

protein that surrounds the cell wall and is sticky, protecting the cell and enabling it to

adhere to substrates or other cells. 2) The sporangium of a bryophyte.

chemoautotroph

An organism that obtains energy by oxidizing inorganic substances

and needs only carbon dioxide as a carbon source.

chemoheterotroph

An organism that requires organic molecules for both energy and

carbon.

commensalism

A +/0 ecological interaction that benefits the individuals of one

species but neither harms nor helps the individuals of the other species.

conjugation

1. In prokaryotes, the direct transfer of DNA between two cells that are

temporarily joined. When the two cells are members of different species, conjugation

results horizontal gene transfer. 2) In ciliates, a sexual process in which two cells

exchange haploid micronuclei but do not reproduce.

decomposers

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.

endospores

A thick

they are exposed to hash conditions.

endotoxins

A toxic component of the outer membrane of certain gram

bacteria that is released only when the bacteria die.

exotoxins

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 halophile

An organism that lives in a highly saline environment, such as the

Great Salt Lake or the Dead Sea.

extreme thermophile

An organism that thrives in hot environments (often 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”).

F factor

In bacteria, the DNA segment that confers the ability to form pili for

conjugation and associate functions required for the transfer of DNA from do nor to

recipient. The F factor may exist as a plasmid or be integrated into the bacterial

chromosome.

F plasmid

The plasmid form of the F factor.

fimbria

(plural fimbriae) A short, hairlike appendage of a prokaryotic cell that helps it

adhere to the substrate or to other cells.

gram

negative

structurally more complex and contains less peptidoglycan than the cell wall of gram

positive bacteria. Gram

negative bacteria are often more toxic than gram

bacteria.

gram

positive

less complex and contains more peptidoglycan than the cell wall of gram

negative

bacteria. Gram

positive bacteria are usually less toxic than gram

heterocysts

A specialized cell that engages in nitrogen fixation in some filamentous

cyanobacteria; also called a heterocyte.

host

The larger participant in a symbiotic relationship, often providing a home and

food source for the smaller symbiont.

methanogens

An organism that produces methane as a waste product of the way it

obtains energy. All known methanogens are in domain Archaea.

mutualism

A +/+ ecological interaction that benefits individuals of both of the

interacting species.

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.

nucleoid

A non

chromosome is located.

parasite

An organism that feeds on the cell contents, tissues, or body fluids of

another species (the host) while in or on the host organism. Parasites harm but usually

do not kill their host.

parasitism

A +/– ecological interaction in which one organism, the parasite, benefits

by feeding upon another organism, the host, which is harmed; some parasites live

within the host (feeding on its tissues), while others feed on the host’s external surface.

pathogens

An organism or virus that causes disease.

peptidoglycan

A type of polymer in bacterial cell walls consisting of modified sugars

cross

linked by short polypeptides.

photoautotroph

An organism that harnesses light energy to drive the synthesis of

organic compounds from carbon dioxide.

photoheterotroph

An organism that uses light to generate ATP but must obtain

carbon in organic form.

pilus

(plural pili) In bacteria, a structure that links one cell to another at the start of

conjugation; also known as a sex pilus or conjugation pilus.

plasmid

A small, circular, double

genes separate from those of a bacterial chromosomes in DNA cloning, can by used as

a vector carrying up to about 10,000 base pairs (10 kb) of DNA.

prokaryotes

An organism that has a prokaryotic cell; an informal term for an

organism in either domain Bacteria or domain Archaea.

protocells

An abiotic precursor of a living cell that had a membrane

that maintained an internal chemistry different from that of its surroundings.

R plasmid

A bacterial plasmid carrying genes that confer resistance to certain

antibiotics.

ribosome

A complex of rRNA and protein molecules that functions as a site of

protein synthesis in the cytoplasm; consists of a large subunit and a small subunit. In

eukaryotic cells, each subunit is assembled in the nucleolus. See also nucleolus.

symbiont

The smaller participant in a symbiotic relationship, living in or on the host.

symbiosis

An ecological relationship between organisms of two different species that

live together in direct and intimate contact.

taxis

An oriented movement toward or away from a stimulus.

transduction

A process in which phages (viruses) carry bacterial DNA from one

bacterial cell to another. When these two cells are members of different species,

transduction results in horizontal gene transfer. See also signal transduction pathway.

transformation

1. The process by which a cell in culture acquires the ability to divide

indefinitely , similar to the division of cancer cells. 2) A change in genotypes 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.