Psychrophiles

Psychrophiles

Psychrophiles

Psychrophiles are capable of growth and reproduction at low temperature. They are also known as cryophiles.

Obligate psychrophiles have a growth temperature optimum of 15℃ or lower. Psychrophiles are contaminants of refrigerated food or dairy products.

Psychrophiles can be used as cell factories for the production of unstable compounds as well as for bioremediation of polluted cold soils and wastewaters.

Examples of psychrophiles are Psychrobacter spp., Arthrobacter spp.,  Halomonas spp., Pseudomonas.

Facultative psychrophiles grow slowly in cold conditions but they have optimum temperature above 20℃.

For example,   Staphylococcus aureus, Listeria monocytogens.

The adaptation of Psychrophiles

The reason behind  the adaptation of psychrophiles to lower temperature is membrane fluidity because of polyunsaturated fatty acids.

At low temperature, membranes and enzymes become rigid. Membrane fluidity is reduced and results in reduced  membrane permeability. That adversely affects transport of nutrients and waste products across the membrane.

But psychrophiles function at low temperature due to adaptations in cellular proteins and lipids that provide a barrier between cytoplasm and extreme environment and help in maintainance of optimal membrane fluidity.

Archaea and bacteria have higher proportion of unsaturated, polyunsaturated and methyl branched fatty acids. They have cis- unsaturated double bonds and antesio branched fatty acids that allow the membrane to remain in a liquid crystalline state.

Membrane permeability is dependent on membrane fluidity. It is essential for the provision of energy,  metabolites and intracellular environment needed for metabolism.

It is also a determining factor for growth. Membrane permeability is linked to proton motive force and sodium motive force. Proton permeability of liposomal membranes in archaea adjust lipid composition to maintain constant homeo- proton permeability.

Psychrophiles

Written By

Sadia Akhtar
Student of Department of Microbiology
Jagannath University.
Email- sadiabd810@yahoo.com