BoO Ch 27: Bacteria and Archaea

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-coating colony of one or more species of unicellular organisms that engage in metabolic cooperation; most known biofilms are formed by prokaryotes

bioremediation

The use of organisms to detoxify and restore polluted and degraded ecosystems

capsule

(1) In many prokaryotes, a dense and well-defined layer of polysaccharide or protein that surrounds the cell wall and is sticky, protecting the cell and enabling it to adhere to substrates or other cells

commensalism

A positive-neutral ecological interaction that benefits the individuals of one species but neither harms nor helps the individuals of the other species

conjugation

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 in horizontal gene transfer. (2) In ciliates, a sexual process in which two cells exchange haploid micronuclei but do not reproduce.

CRISPR-Cas9 system

A technique for editing genes in living cells, involving a bacterial protein called Cas9 associated with a guide RNA complementary to a gene sequence of interest

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

extremophile

An organism that lives in environmental conditions so extreme that few other species can survive there

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 to 80 degrees C or hotter)

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

fimbria (fimbriae)

A short, hairlike appendage of a prokaryotic cell that helps it adhere to the substrate or to other cell

gram-negitive

Describing the group of bacteria that have a cell wall that is structurally more complex and contains less peptidoglycan than the other group; often more toxic than other group; appear pink

gram-positive

Describing the group of bacteria that have a cell wall that is structurally less complex and contains more peptidoglycan than the other group; appear more purple

Gram stain

method that distinguishes between two different kinds of bacterial cell walls; may be used to help 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 positive-positive ecological interaction that benefits individuals of both interacting species

nitrogen fixation

The conversion of atmospheric nitrogen (N₂) to ammonia (NH₃) is carried out by certain prokaryotes, some of which have mutualistic relationships with plants

nucleiod

A non-membrane-enclosed region in a prokaryotic cell where its chromosome is located

obligate aerobe

An organism that requires oxygen for cellular respiration and cannot live without it

obligate anaerobe

An organism that carries out only fermentation or anaerobic respiration. Such organisms cannot use oxygen and in fact may be poisoned by it.

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; usually harm but do not kill host

parasitism

A positive-negative 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

pathogen

An organism or virus that causes disease

peptidoglycan

a polymer in bacterial cell wall consisting of modified sugars cross-linked by short polypeptides

pilus (pili)

In bacteria, a structure that links one cell to another at the start of conjugation;

plasmid

A small, circular, double-stranded DNA molecule that carries accessory genes separate from those of a bacterial chromosome; also found in some Eukaryotes, such as yeasts

prokaryote

A single-celled organism of the domain Bacteria or Archaea

R plasmid

A bacterial plasmid carrying genes that confer Resistance to certain antibiotics

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, it results in horizontal gene transfer;

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, it results in horizontal gene transfer