Key Terms

acidophile

organism with optimal growth pH of three or below

aerobic

organisms that use oxygen

alkaliphile

organism with optimal growth pH of nine or above

ammonification

process by which ammonia is released during the decomposition of nitrogen-containing organic compounds

anaerobic

refers to organisms that grow without oxygen

anoxic

without oxygen

antibiotic

biological substance that, in low concentration, is antagonistic to the growth of prokaryotes

autotroph

organism that produces organic molecules from small inorganic compounds

biofilm

microbial community that is held together by a gummy-textured matrix

biological nitrogen fixation

conversion of atmospheric nitrogen into ammonia exclusively carried out by prokaryotes

bioremediation

use of microbial metabolism to remove pollutants

biotechnology

any technological application that uses living organisms, biological systems, or their derivatives to produce or modify other products

Black Death

devastating pandemic that is believed to have been an outbreak of bubonic plague caused by the bacterium Yersinia pestis

botulism

disease produced by the toxin of the anaerobic bacterium Clostridium botulinum

CA-MRSA

MRSA acquired in the community rather than in a hospital

capsule

external structure that enables a prokaryote to attach to surfaces and protects it from dehydration

chemotroph

organism that obtains energy from chemical compounds

conjugation

process by which prokaryotes move DNA from one individual to another using a pilus

cyanobacteria

bacteria that evolved from early phototrophs and oxygenated the atmosphere; also known as blue-green algae

decomposer

organism that carries out the decomposition of dead organisms

denitrification

transformation of nitrate from soil to gaseous nitrogen compounds such as N₂O, NO, and N₂

emerging disease

disease making an initial appearance in a population or that is increasing in incidence or geographic range

endemic disease

disease that is constantly present, usually at low incidence, in a population

epidemic

disease that occurs in an unusually high number of individuals in a population at the same time

extremophile

organism that grows under extreme or harsh conditions

foodborne disease

any illness resulting from the consumption of contaminated food, or of the pathogenic bacteria, viruses, or other parasites that contaminate food

Gram negative

bacterium whose cell wall contains little peptidoglycan but has an outer membrane

Gram positive

bacterium that contains mainly peptidoglycan in its cell walls

halophile

organism that require a salt concentration of at least 0.2 M

heterotroph

organism that obtains energy from organic molecules

hydrothermal vent

fissure in Earth’s surface that releases geothermally heated water

hyperthermophile

organism that grows at temperatures between 80–122 °C

microbial mat

multi-layered sheet of prokaryotes that may include bacteria and archaea

MRSA

(methicillin-resistant Staphylococcus aureus) very dangerous Staphylococcus aureus strain resistant to multiple antibiotics

nitrification

conversion of ammonium into nitrite and nitrate in soils

nitrogen fixation

process by which gaseous nitrogen is transformed, or “fixed” into more readily available forms such as ammonia

nodule

novel structure on the roots of certain plants (legumes) that results from the symbiotic interaction between the plant and soil bacteria, and is the site of nitrogen fixation

nutrient

essential substances for growth, such as carbon and nitrogen

osmophile

organism that grows in a high sugar concentration

pandemic

widespread, usually worldwide, epidemic disease

peptidoglycan

material composed of polysaccharide chains cross-linked to unusual peptides

phototroph

organism that is able to make its own food by converting solar energy to chemical energy

pilus

surface appendage of some prokaryotes used for attachment to surfaces including other prokaryotes

pseudopeptidoglycan

component of archaea cell walls that is similar to peptidoglycan in morphology but contains different sugars

psychrophile

organism that grows at temperatures of -15 °C or lower

radioresistant

organism that grows in high levels of radiation

resuscitation

process by which prokaryotes that are in the VBNC state return to viability

S-layer

surface-layer protein present on the outside of cell walls of archaea and bacteria

serotype

strain of bacterium that carries a set of similar antigens on its cell surface, often many in a bacterial species

stromatolite

layered sedimentary structure formed by precipitation of minerals by prokaryotes in microbial mats

teichoic acid

polymer associated with the cell wall of Gram-positive bacteria

thermophile

organism that lives at temperatures between 60–80 °C

transduction

process by which a bacteriophage moves DNA from one prokaryote to another

transformation

process by which a prokaryote takes in DNA found in its environment that is shed by other prokaryotes

viable-but-non-culturable (VBNC) state

survival mechanism of bacteria facing environmental stress conditions

zoonosis

disease that primarily infects animals that is transmitted to humans