F3 Microbial diversity Flashcards
Factors that influence growth
- temperature
- pH (acidic, alkaline conditions)
- salts
- pressure (osmotic or physical)
- light
- oxygen
- radiation
?: greek for loving, an organism that thrives in a certain condition
?: an organism that can endure a certain condition
?: organism growing under ’normal’ conditions
-phile
-tolerant
mesophile
extremophiles are often archaea, but bacteria and fungi can be extremophiles as well
examples of extremophiles:
- thermophile (hot springs, over 100 °C possible)
- psychrophile (ice caps, up to -20 °C)
- acidophile (acid mine drainage)
- alkaliphile (soda lakes, often also halophile)
- halophile (salt lakes)
- piezophile (deep sea, often also psychrophile)
temperature affects the membrane …
fluidity
Adaptation to extreme temperatures, Psychrophiles:
proteins
• more alpha helices, less beta sheets
• more polar, less hydrophobic amino acids
• fewer protein-protein interactions
membranes
• short fatty acids
• unsaturated fatty acids
• branched fatty acids
stress repsonses
• cold shock proteins (stabilize RNA)
• cryoprotectants (e.g. glycerol)
Adaptation to extreme temperatures, Thermophiles:
proteins • more beta sheets, less alpha helices • more hydrophylic amino acids on the surface (increased interactions) • many hydrophobic amino acids in the core (protection against unfolding in aqueous environments) • many protein-protein interactions
membranes
• long, unbranched fatty acids
• fully saturated lipids
• isoprene lipids (similar to cholesterol)
stress responses
• heat shock proteins
why is thermophiles and their enzymes interesting for biotechnology?
+ give examples of use
- higher temperture -> higher reaction speed -> more efficient production
- less risk of contamination
- thermostable enzymes are often generally more stable
examples of use:
• PCR polymerases (thermostability)
• biofuel production (butanol resistance)
Acidophiles
• viable at acidic conditions (pH 1-5)
• extreme: Picrophilus oshimae optimum pH 0.7, 60 °C
• many yeasts (e.g. baker’s yeast) can survive at pH 2.5 to over 7
• many bacteria (lactic acid bacteria, acetobacteraceae)
• most pathogens do not like low pH
-> conservation method (sauerkraut)
-> skin pH 5.5
-> exception: Helicobacter pylori (stomach ulcers)
Alkaliphiles
• viable at high pH (8-11)
• produce many alkaline-stable enzymes, e.g. lipases, proteases
-> laundry detergent
- acidic conditions can damage … , proteins, and membranes
- alkalic conditions can damage … , proteins, and membranes
RNA
DNA
both acidophiles and alkaliphiles regulate their intracellular pH by …
transport of H+
- obligate aerobe: …
- obligate anaerobe: …
- facultative anaerobes: …
- aerotolerant anaerobes: …
- microaerophiles: …
- obligate aerobe: needs O2
- obligate anaerobe: O2 is toxic
- facultative anaerobes: grow better with O2 but can also live under anaerobic conditions
- aerotolerant anaerobes: do not need O2 to grow, but are not sensitive to it
- microaerophiles: need a specific level of low O2 concentrations
Growing aerobic bacteria
- never fill up a flask completely (10% of the volume)
- always shake
- oxygen depletion -> stress
- once cells shift to anaerobic metabolism, it takes time to adapt to aerobic metabolism again (long lag phase)
Growing anaerobic bacteria
- N2 to deplete O2
- Anaerob jar with Petri plates
- Openings of an anaerobic box sealed by glove-like sleeves for handling of cultures inside the box
examples of anaerobic microbes (fermentation: no O2)
lactic acid bacteria, yeast
