TABLE 5.1 Microbial Diversity: Selected Terminology

 

Description

Type Diversity

Prokaryotes

A general term that encompasses bacteria and archaea, microbial cells that lack a nuclear membrane surrounding their chromosomal DNA, a cytoskeletal matrix, and other membrane-bounded organelles such as mitochondria and chloroplasts

Bacteria

One of the three known domains of life: microbial cells lacking nuclear bound chromosomes with predominantly diacyl glycerol diester membrane lipids

Archaea

One of the three known domains of life: microbial cells lacking nuclear bound chromosomes with predominantly isoprenoid glycerol diethers or diglyceral tetraether membrane lipids

Eukarya

One of the three known domains of life with nuclear bound chromosomes, cytoskelatal organizing matrices, predominantly glycerol fatty acyl diester membrane lipids, and other membrane-bounded organelles such as mitochondria and chloroplasts

Psychrophile

Capable of growth at low temperatures, with an optimal growth temperature below 15°C

Psychrotroph

Capable of growth at low temperatures, with an optimal growth temperature greater than 15°C

Mesophile

Generally defined by optimal temperature for growth, usually between 25°C and 40°C, but often capable of growth from 8°C to 50°C

Thermophile

Optimal temperature for growth is greater than 45°C but not above 80°C

Hyperthermophile

Optimal temperature for growth is 80°C or above

Acidophile

Grows at pH values less than 5

Alkalophile

Grows at pH values greater than 9

Neutrophile

Grows with optimal rates near pH 7

Halophile

Requires high salt concentrations (>2.5 M) for growth

Xerophile

Capable of growing under conditions of low water activity (effective water content)

Barophile

Obligate barophiles are unable to grow at 1 atmosphere of pressure; barotolerant bacteria grow at 1 atmosphere and higher pressures; all barophiles grow optimally under high pressure

Physiological Diversity

Aerobe

Capable of using oxygen as terminal electron acceptor; can tolerate levels of oxygen at or greater than 21 percent and has a strictly respiratory-type metabolism

Anaerobe

Grows only in the absence of oxygen; most have fermentative-type metabolism, but some carry out anaerobic respiration using terminal electron acceptors other than oxygen

Facultative anaerobe

Can grow aerobically or anaerobically

Microaerophile

Capable of oxygen-dependent growth at oxygen levels well below 21 percent

Autotroph

Uses carbon dioxide as its sole source of carbon

Heterotroph

Unable to use carbon dioxide as a sole source of carbon and requires one or more organic compounds

Chemoorganoheterotroph

Derives energy from chemical compounds and uses organic compounds as a reductant

Chemolithoautotroph

Relies on reduced chemical compounds as a source of energy and carbon dioxide as a source of carbon; includes hydrogen bacteria, iron bacteria, sulfur bacteria, ammonia oxidizers, nitrite oxidizers obligate methane oxidizers, carbon monoxide oxidizers

Mixotroph

Capable of growing both chemoorganoheterotrophically and chemolithoautotrophically

Oligotroph

Capable of growth on minimal media (1 to 15 µg carbon per liter)

Copiotroph

Requires nutrients at levels 100 times those of oligotrophs

 

SOURCE: Madigan et al. (2002).



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