Ecosystems - Extremophiles - Pearson PDF

Extremophiles 2 Section 4.11- 4.16 pp 126-137 Extremophiles: Organisms that prefer conditions outside the limits of what is “normal” PHOTO: Christine Sharp IMAGE: Dewar Creek...

Extremophiles 2 Section 4.11- 4.16 pp 126-137 Extremophiles: Organisms that prefer conditions outside the limits of what is “normal” PHOTO: Christine Sharp IMAGE: Dewar Creek BC- Canada’s hottest geothermal spring (84oC)  Thermophiles and Biotechnology The Cetus corporation (Roche) is estimated to have made $2 billion Mushroom Spring in royalties (and a Nobel Prize for US National Parks Service https://www.nps.gov/features/yell/slidefile/thermalfeatures/ Kary Mullis) Tom Brock and Yellowstone National Park received nothing The ATCC got $100 Yellowstone now signs long-time revenue-sharing agreements Taq polymerase IMAGE: Yakrazuul Wikipedia, Public Domain Thermus aquaticus Photos T Brock? public domain Figure 4.22 Antarctic Microbial Habitats and Microorganisms Microbial Life at Low Temperatures Problems: 1) Proteins too rigid and slow reaction rates 2) Membranes too viscous 3) DNA/RNA too rigid Solutions: 1) Reduced amino acid interactions that stabilize tertiary structures 2) Increased membrane fluidity 3) Decreased G+C content Effects of pH on Microbial Growth Each microbe has a pH range ~2–3 pH units within which growth is possible Neutrophiles: organisms that grown optimally within a pH range of 5.5 – 7.9 Alkaliphiles: grow best at high pH (≥ 8) –Champion alkaliphile Natronobacterium gregoryi (archaeon) optimum 10, maximum 12 Acidophiles: grow best at low pH (< 5.5) –champion acidophile: Picrophilus torridus (from sulfur fumaroles) grows at pH 0 The problem The cytoplasm must be near neutral pH Minimum 4.6 and maximum 9.5 are recorded extremes The cell membrane must therefore be very impermeable to protons It is difficult to maintain a proper proton motive force in both extremes  pH and the pmf Acidophiles pH 3 out H+ proton pump to e.t.c. H+ H+ maintain cellular H+ H+ H+ H+ neutral pH H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ ADP pmf: acid out H+ H+ and charge (+) ATP out = ATP F0F1 production pH 7 in ATPase  pH and the pmf Alkaliphiles pH 10 out H+ proton pump to e.t.c. H+ maintain cellular H+ H+ neutral pH H+ H+ H+ H+ H+ H+ H+ H+ alkaline out H+ H+ = NO pmf H+ H+ = no ATP F0F1 produced pH 7 in ATPase  pH and the pmf Na+/ H+ Alkaliphiles antiporter pH 10 out Na+ Na+ Na+ H+ H+ Na+ Na+ proton pump to Na+ Na+ maintain cellular e.t.c. H+ Na+ neutral pH H+ Na+ Na+ Na+ Na+ H+ H+ H+ + Na+ H Na+ Na+ H+ H+ H+ H+ ADP NO pmf Na+ H+ Na+ Na+ but high [Na+] H+ ATP out = smf H+ F0F1 pH 7 in ATPase (Na+ type) Osmotic stress, salt stress Saline spring in Wood Buffalo National Park (P Dunfield)  Osmotic stress, salt stress Halophiles (salt)- Bacteria, Archaea and Eukarya Xerophiles (dry conditions)- especially fungi Osmophile (osmotic stress- in principle any osmotic stress, but the term is by convention applied to organisms adapted to high sugar concentrations) - usually yeasts HALOPHILES: Seawater = 3.5% w/w, mostly NaCl Hypersaline (=more salt than seawater) NaCl saturation 35.8 % Non-halophile: 0% optimum Halophile 1-15% optimum Extreme halophile: >15% optimum Halotolerant Figure 4.27 Osmolarity and Microbial Growth Water activity is a measure of the vapor pressure (or free energy) of water, where aw = 1 for pure water at atmospheric pressure. Lower values are caused by dryness and solutes Typically, the cytoplasm has a higher solute concentration (=lower water activity) than the surrounding environment; thus, the tendency is for water to move into the cell. aw(in) < aw(out) H2O Osmolarity and Microbial Growth As water moves in, the increased pressure in the cell increases the water activity inside, eventually balancing out the solute effect aw(in) = aw(out) Pressure H2O Osmolarity and Microbial Growth What would happen to a normal freshwater bacterium if the aw(out) is very low due to high salt content? aw(in) > aw(out) H2O Strategies of halophiles 1) “Salt in” strategy: accumulate KCl (need salt- adapted enzymes) mostly Archaea (few Bacteria) 2) “Compatible solutes” strategy accumulate organic solutes Bacteria and Eukarya. Compatible solutes, unlike salts, do not damage enzymes Table 4.6 Compatible Solutes of Microorganisms Major cytoplasmic Organism group and example compatible solute(s) Minimum aw for growthc Most nonphototrophic Bacteria Amino acids (mainly glutamate 0.98 (Escherichia) and freshwater or prolinea)/sucrose, trehaloseb cyanobacteria (Anabaena) Marine cyanobacteria (Synechococcus) α-Glucosylglycerolb 0.92 Marine algae (Phaeocystis) Mannitol,b various glycosides, 0.92 dimethylsulfoniopropionate Halotolerant Bacteria (Staphylococcus) Amino acids 0.90 Salt lake cyanobacteria (Aphanothece) Glycine betaine 0.75 Halophilic phototrophic purple Bacteria Glycine betaine, ectoine, 0.75 (Halorhodospira) trehaloseb  Figure 17.2 Figure 17.4 Lake Hamara, Egypt Halobacterium can use light to make ATP via a very simple system Bacteriorhodopsin  Oxygen and Microbial Growth Aerobes: Require O2 for respiration Microaerophiles: Require O2 but at low [ ] Facultative anaerobes: Will respire if O2 is available, but can survive without it Aerotolerant anaerobes: Do not use O2 but can tolerate it Obligate anaerobes: Don’t use O2 nor can they tolerate it Oxygen and Microbial Growth Thioglycolate broth –Complex medium that distinguishes microbes based on oxygen requirements –Resazurin reacts with oxygen, so oxygen can penetrate only a few mm from the top of the tube Figure 4.28 Growth Versus O2 Concentration Oxygen and Microbial Growth Why is oxygen toxic? – Molecular oxygen (O2) has low toxicity… – Exposure to oxygen yields toxic byproducts – The reactive oxygen species (ROS): Superoxide anion (O2-) Hydrogen peroxide (H2O2) Hydroxyl radical (OH ) Figure 4.31: Enzymes that remove ROS Copyright © 2021, 2018, 2015 Pearson Education, Inc. 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