3 physchrophiles Flashcards
Obligate psychrophiles:
Grow and reproduce below 15C (optimum) and colonise -60C environments
Halophiles:
saline conditions
organisms in snow
high uv radiation
Bacterial psychrophiles (unicellular)
- Modify the environment to make water available
- Brine: Water saturated or nearly saturated with salt. Contain small amounts of liquid water at temperatures lower than -30C
- Important to model life on Mars/ other icy bodies
Antifreeze proteins
- Combination of protease and glycoprotein makes an antifreeze glycoprotein (AFGP) which rose from pancreatic trypsinogen-like protease gene
- Associates with water and prevents freezing
Challenges of low temperatures
1) Lower rate of biochemical reactions
For every 10C drop there is reduction of factor of 2 in rate of reactions e.g. DNA synthesis and replication
2) Increase in viscosity, decline in mobility
3) Reduction in membrane lipid fluidity
4) Decrease protein flexibility
Cells cooled too slowly
= outside environment freezes first then extracellular ice = membrane potential = water flows outside cell = cell shrinks = dehydration = irreversible damage
cells cool too quick
Cells cooled too quickly = retain water in cell = water expands when frozen = ice crystals physically destroy cell = intracellular injury
1) Problem: increased viscosity and decreased mobility
o Freezing avoidance – salts and solutes plus antifreeze cryoprotectant proteins (glycoproteins) lower freezing point by 10-20C
o Reduce the severity of dehydration effects and prevent ice crystals inside
o EXAMPLE: Antarctic fish can survive with small ice crystals present in body fluids
o Freezing tolerance: Allow external environment to freeze
o This insulates the cell against internal freezing due to change in thermal conductivity
problem: decreased fluidity in the membrane
1 Ratio of unsaturated to saturated hydrocarbons increased so freezing point changes
2 Unsaturated have more double C-C bonds which means can bend and packed less tightly
3 Change in lipid composition
3) Problem: decreased protein flexibility
o Changes in structure of cell’s proteins, use enzymes with fold and shapes which promote less rigidity
o Reduction in ion pairs, hydrogen bonds and hydrophobic interactions = more reactions with water
o Decreased intersubunit interactions and increased interaction with solvent = minimise polymers and less cofactor binding
o Higher accessibility to active site as more ridged
o Clustering of glycine, lower proline and arginine = favour B sheets over A helices
- Increased heat shock proteins (chaperones which assist in protein folding/conformation) when temperature is lowered
- Form spores or cysts to outlast cold period
Applications of psychrophiles (7)
1) Efficient enzymes which work in the cold e.g. milk, cheese, tenderising meat, jams
2) Food processing
o High levels of xylose increase water retention in dough
o Xylanases improves dough fermentation
o P. haploplanktis is protobacteria from Antarctic sea ice
o Aim to engineer yeasts with hydrolases
3) Perfumes, most don’t tolerate high temperatures
4) Cold-wash detergents, ligases
5) Biofuels, ethanol production, high flammability so low temperature needed
6) Medicines, pharmaceuticals
7) Aquaculture and animal health care products
Bioremediation
Bioremediation: Biotechnology which uses biological processes to overcome environmental problems, uses natural biological activity e.g. microbes or fungi
- Used to degrade xenobiotics (human made toxic compounds) through human error or negligence
- Thermophiles AND psychrophiles used
- EXAMPLE: major oil spills in 20th/21st century such as Gulf War
- EXAMPLE: Chernobyl (nuclear power reactor explosion
conventional techniques of bioremediation
- Dig up contaminated soil and remove to landfill
- Cap and contain contaminated areas
- Destroy pollutants or make harmless e.g. UV oxidation
Disadvantages: Expensive, small scale, lack of public acceptance, can make more toxic
