Microbial Terms

Obligate Aerobes
An aerobic prokaryote that cannot survive without oxygen (O2).
Obligate Anaerobes
An anaerobic prokaryote that cannot survive exposure to oxygen (O2).
Facultative Anaerobes
A prokaryote that can shift its metabolism between anaerobic and aerobic operations modes on the presence or absence of O2.
Psychrophiles
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Organisms such as fungi and bacteria that show optimum growth at extremely low temperatures. (optimum temp)
Mesophiles
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-majority of medically significant microorganisms
-grow at intermediate temperatures between 20°C and 40°C
-inhabit animals and plants as well as soil and water in temperate, subtropical, and tropical regions
-human pathogens have optimal temperatures between 30°C and 40°C
Thermophiles
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-grows optimally at temperatures greater than 45°C
-live in soil and water associated with volcanic activity, compost piles, and in habitats directly exposed to the sun
-vary in heat requirements with a range of growth of 45°C to 80°C
-most eukaryotic forms cannot survive above 60°C
•Extreme thermophiles grow between 80°C and 121°C
Acidophiles
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Organisms that thrive in acidic environments

-Euglena mutabilis: grows in acid pools between pH 0 and 1
-Thermoplasma: lives in coal piles at a pH of 1 or 2
-Picrophilus: thrives at a pH of 7, but can live at a pH of 0
-Many molds and yeasts tolerate acid and are the primary spoilage agents of pickled foods

Halophiles
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Prefer high concentration of salt

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-Obligate halophiles Halobacterium and Halococcus grow optimally at solutions of 25% NaCl but require at least 9% NaCl
-Facultative halophiles: remarkably resistant to salt, even though they do not normally reside in high salt environments
-Staphylococcus aureus can grow on NaCl media ranging from 0.1% to 20%

Alkalophiles
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Organisms that thrive in alkaline conditions

-Natromonas: live in hot pools and soils at pH 12
-Proteus: can create alkaline conditions to neutralize urine and colonize and infect the urinary system

Neutrophiles
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The majority of organisms live or grow in habitats between pH 6 and 8 because strong acids and bases can be damaging to enzymes and other cellular substances
Halotolerant
The adaptation of living organisms to conditions of high salinity. Halotolerant species tend to live in areas such as hypersaline lakes, coastal dunes, saline deserts, salt marshes, and inland salt seas and springs. Halophiles live in highly saline environments, and require the salinity to survive, while halotolerant organisms (belonging to different domains of life) can grow under saline conditions, but do not require elevated concentrations of salt for growth.
Osmophiles
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live in habitats with high solute concentration
Xerophiles
Plant/organism adapted for life with a limited supply of water/..
Endotoxin
A toxin that is confined inside the microorganisms and is released only when the microorganisms are broken down or die.

A lipopolysaccharide that forms part of the outer membrane of certain gram negative bacteria that is released when the bacteria grow or lyse (destruction).

Exotoxin
A toxin that is secreted by microorganisms into the surrounding medium.

A highly toxic, usually soluble protein released by living, multiplying bacteria.