Microbial Life in Very Cold EnvironmentsCreated by: Scott N. Montross, Montana State University
"Psychrophiles are defined as organisms having an optimal temperature for growth at about 15ºC or lower, a maximal temperature for growth at about 20º C, and a minimal temperature for growth at 0º C or below."
-Morita, R.Y. (1975) Psychrophilic bacteria. Bacteriol. Rev.39:144-167.
What are psychrophiles?
Psychrophiles are commonly described as microorganisms which exhibit a growth temperature optimum of 15°C and lower. The recent discovery of cold-tolerant microorganisms in glaciated and permanently frozen environments has broadened the known range of environmental conditions which support microbial life. Psychrophilic bacteria belong to four phylogenetic groups, the alpha and gamma subdivisions of the Proteobacteria, the Flexibacter-Bacteroides-Cytophaga phylum and the gram-positive branch. Isolates from cold environments include Arthrobacter sp., Psychrobacter sp., and members of the genera Halomonas, Pseudomonas, Hyphomonas, and Sphingomonas
Why are psychrophiles COOL?
Recent investigations have shown psycrophily is more prevalent than previously believed. Psychrophilic bacteria are represented in all three domains of life, many of these organisms are methanotrophs, sulfate reducers, iron oxidizers, and methanogens.
Psychrophilic bacteria have:
-adapted to their cool environments by having largely unsaturated fatty acids in their plasma membranes. Some psychrophiles have been found to contain polyunsaturated fatty acids, which generally do not occur in prokaryotes
-enzymes that continue to function, albeit at a reduced rate, at near freezing ambient temperatures
-the ability to produce proteins that are stable at cold temperatures
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