6.4 Environmental limits on Microbial growth

“Typical” physiologic conditions vary, but generally considered:

• Temperature between 20-40°C (68-104°F)

• near-neutral PH

• salt concentration of .9%

• and ample nutrients

Extremophiles

• bacteria, archaea, and some eukaryotic microbes that can grow in extreme environments where most organisms cannot

Classification is based on the range of ______ temperatures

Optimal

Psychrophile

0-20°C

• Fridge-room temp

Mesophile

40°C: optimal

• Body temp

Thermophile

60°C

• Optimal above compost

Hyperthermophile

>80°C

• little under boiling

Microorganisms can _____, and even grow, at ____ _____ of temperature, even if not optimal

• might grow slowly or not at all at colder temps

survive; wide ranges

Pressure: Barophiles (piezophiles)

microorganisms deep within the ocean that have adapted to grow at oppressively high pressures

• Mariana Trench

Pressure: Adaptations

Adapted membranes and amino acid sequences in proteins

Water availability and salt concentration: Halophiles

Microorganisms that have evolved to require high concentrations of salt (NaCl)

• ….Thrive!

Water availability and salt concentration: Adaptation

Additional sodium ion pumps to maintain osmotic balance and avoid plasmolysis

Halotolerant microbes

Can deal with moderately high salt concentrations

• but don’t necessarily thrive or survive in extreme concentrations

Adaptation: PH

• these extremophiles pump protons (H+)

• into or out of the cell maintain a Neutral Internal pH

*acid Tolerant microbes

• can survive and maybe grow at acidic pH, but don’t thrive at very low pH

• Ex. Helicobacter pylori (stomach) makes urease

  • Not an extremophile

Adaptation: PH

• these extremophiles pump protons (H+)

• into or out of the cell maintain a Neutral Internal pH