Mechanisms of Adaptations of Hyperthermophiles and Acidophiles

Mechanisms of Adaptations of Hyperthermophiles and Acidophiles

Mechanisms of Adaptations of Hyperthermophiles and Acidophiles

Hyperthermophiles

Hyperthermophiles are super-heat loving bacteria. They are mainly bacteria and archaea.
Hyperthermophiles are found within environments with highly temperature. Optimal temperature for hyperthermophiles is > 80⁰ degree Celsius.

Hyperthermophiles synthesize enzymes called hyperthermophilic enzymes and these enzymes are active at high temperatures.
Hyperthermophiles are primary producers and decomposers of organic matter, chemolithoauyotrophs - sulfur oxidizers, sulfur reducers, methanogens.

1. DNA structure:

a) high content of GC pairings, GC have three H - bonds which provide stability to DNA at such high temperature that creates enough terminal energy to separate the DNA strands.

b) high temperature stable type 1 topoisomerase protein that supertwists DNA making stable.

2. Membrane adaptation:

a)     Archaea have ether linkages in their membrane instead of ester linkages. Ether links make bonds more stable between phosphate groups and hydrocarbons making the carbon connecting phosphates and glycerol molecule less electrophilic and less chemically reactive.

b) Tetraether phospholipids are found in P. fumarii and other hyperthermophiles. Tetraether phospholipid contains two hydrocarbon tails each coming from one ester bond and one phosphate molecule.
These phospholipids form monolayers instead of bilayers seen in many bacteria.

This decreases membrane fluidity to decrease the movement of phosphate molecules, which stops the unwanted movement of molecules across the membrane.

3. Metabolism:

a)     Archaea have needed to devise unusual ways to gather energy from environment and protect themselves against heat.
P. fumarii like plants, are able to harvest carbon dioxide from environment to bind their biomolecules.
Unlike plants, they take electrons from hydrogen instead of water and transfer those electrons to nitrate, sulfate or oxygen. This type of metabolism is called chemolithoautotrophism.

b)    Hyperthermophiles ensure their proper protein function through the use of heat shock protein (HSPs). HSPs act as chaperone proteins that help enzymatic proteins maintain their proper conformation at such high temperatures.

Acidophiles

Acidophiles are microorganisms thrive in naturally acidic environments such as sulfuric pools, mines, metal ores ( under pH 2.0) .

Acidophiles produce enzymes functional at lower pH. These enzymes maybe proteases, ligases, esterases, endoglucanases, xylanases,cellulases. They are used in polymer degradation. 

Examples of Acidophiles are Thiobacillus acidophilus, Ferroplasma,
Thiobacillus thiooxidans, Sulfolobus acidocaldarius.

1. Membrane impermeability to protons:

Acidophiles contain tetraether phospholipids in their impermeable membranes which are less sensitive to acid hydrolysis than ester linkages.

2. Inhibition of proton influx by chemiosmotic gradient:

Influx of potassium ions than an outflux of hydrogen ions.

3. Active pumping out of excess protons:

Using secondary transporters such as hydrogen ion ATPases, symporters and anti porters.

4. Cytoplasmic buffering:

Bacillus acidocaldarium acidophile has a higher buffering ability and can maintain pH homeostasis by buffering.

5. DNA and protein repair:

DNA and proteins are demanded at low pH. Several acidophiles genomes contain a large number of DNA and protein repair genes. Chaperones are involved in protein folding.

6. Intracellular enzymes stabilized by metal cofactors:

The   Ferroplasma acidiphilum proteome contain a high proportion of iron protein that contribute to pH stability of enzymes at low pH.

Mechanisms of Adaptations of Hyperthermophiles and Acidophiles

Written By

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