Psychrophile
Psychrophilie ( from Ancient Greek ψυχρός psychrós "cold", " cool " and φίλος philos " loving" ) is the property of living beings to prefer low temperatures. Living things with this property are called psychrophilic ( cold- loving) called. Psychrophilic microorganisms are among the extremophiles. They usually thrive at -5 to 20 ° C. An increase in the psychrophilic represent the Kryophilen, which have specialized in temperatures below -10 ° C.
Overview of the temperature requirements in bacteria
Psychrophilic bacteria have a growth optimum at 15 ° C, but can live well below freezing even in temperatures. Psychrotolerante microorganisms, however, tolerate low temperatures, but can not grow below 3-5 ° C. You play for many biotechnological fermentation processes play an important role ( see below). The table shows the approximate, overlapping temperature ranges are listed, which can be divided into several classes:
True psychrophilic organisms (also referred stenopsychrophil ) can not tolerate higher temperatures for growth, whereas psychrotolerant organisms (also referred eurypsychrophil ) prefer low temperatures, but also withstand temperatures up in the mesophilic range.
Occurrence
Psychrophilic microorganisms are often found in alpine and polar regions such as the Arctic ( Greenland ) and Antarctica, where they trapped in the ice live in tiny liquid bubbles, which are barely larger than themselves live this addition in deep, cold water layers of oceans and are at the same time barophil. ( Shewanella benthica; ; Flavobacterium islandicum; Photobacterium profundum Gallionella ) The microorganisms are often among bacteria and archaea ( Methanogenium frigidum, Methanococcoides burtonii, Halorubrum lacusprofundi ), but also fungi and microalgae ( Chlamydomonas nivalis). The latter is known as Schneealge and stained the snow and glacier surfaces by its red spores ( blood snow).
Example: Chryseobacterium greenlandensis
An example of simultaneously psychrophilic and barophilic bacteria was discovered in the inland ice of Greenland. Of less than 0.2 microns wide organism is able to survive long periods in habitats with low temperatures, high pressure and low oxygen and nutrient content. He has survived more than 120,000 years in a depth of about 3,000 meters.
The bacterium was discovered at the Pennsylvania State University and presented by Jennifer Loveland - Curtze and colleagues first time at the annual meeting of the American Society for Microbiology on 3 June 2008 to the public. Assign it the Flavobacteriaceae family in the root Bacteroidetes and to propose " Chryseobacterium greenlandensis " as a name before.
Adaptation
Most of the enzymes of psychrophilic microorganisms are similar to those specially adapted for the thermophilic microorganisms these living conditions. Compared to the psychrotolerant organisms at low temperatures - at slower growth - survive, psychrophilic organisms can proliferate under these conditions.
Here, the cell membrane of the organism containing a high proportion of polyunsaturated fatty acids with shorter chain length and increasing branching. This is to ensure that the membrane is sufficiently fluid at low temperatures and does not solidify. In addition, the enzymes at low temperatures are sufficiently flexible and thermolabile. Finally, the cytoplasm of those psychrophilic must remain liquid and prevent the formation of ice crystals. Seaweed such a " antifreeze " for example glycerol.
Biotechnological importance
Psychrophilic microorganisms or psychrotolerante ( Brochothrix thermosphacta; Pseudomonas fragi ) can be a problem in the storage of refrigerated foods present. This can significantly contribute to destruction despite low temperatures. Yersinia enterocolitica, Listeria monocytogenes, Clostridium botulinum and Bacillus cereus are also pathogenic for humans.
On the other hand, beer, and many dairy products (cheese, yogurt ) is produced with the help of psychrotolerant microorganisms. This therefore play an important role for the biotechnological fermentation.