Lecture 18. Diversity of Microbial Life Lecture 18. Diversity of Microbial Life.  What Do Microbes Need to Survive?  Energy and Metabolism.  Extremophiles, Photosynthesis, and Chemosynthesis. EXAM1: High: 88 Low: 55 Average: 72.2 reading: Chapter 6

Pervasiveness of Life Earth life extraordinarily successful Natural selection & evolution --> adaptability Organisms found EVERYWHERE glaciers & permafrost hot springs hydrothermal vents desert rocks clouds deep sea sediments soils Snow algae on glacier Sierra Nevada, CA

Five Things You Need to Have Life Stable Environment be able to adapt to changes Liquid water -20˚C to 121˚C Energy Source O2 and carbohydrates oxidant (O2) and reductant (sugars) Carbon Source carbohydrates sometimes different from an energy source Nutrients The Biogenic Elements: C, H, N, O, P, S Trace Nutrients: Ca, Fe, Cu, Zn, vitamins….. some organisms need more than others when considering the potential for life elsewhere:

Liquid Water If T below 0˚C, microbes can be found growing between ice crystals or in the pore spaces of ice. Microbes can secrete compounds that can inhibit ice crystal formation. Soil still contains substantial thin films of liquid water below 0˚C … could be important for life on Mars.

Energy Sources Light Energy - photosynthesis phototroph convert light energy into chemical energy (ATP) Inorganic Compounds chemotroph, lithotroph need an oxidant: O2, SO42- (sulfate), NO3- (nitrate), Fe3+ need a reductant: H2, H2S (sulfide), Fe2+, Mn2+ react oxidant and reductant, convert to ATP Organic Compounds organotroph need an oxidant organic compounds as a reductant: glucose, cellulose

Carbon Source CO2 autotrophs organic carbon heterotrophs Can combine words for energy and carbon sources: Name Energy Source Carbon Source Photoheterotroph Light Organic C Photoautotroph CO2 Chemoorganotroph Organic (reductant) and inorganic chemicals (oxidant) Chemoautotroph Inorganic chemicals (reductant & oxidant)

Five Things You Need to Have Life Also need Nutrients The Biogenic Elements: C, H, N, O, P, S Trace Nutrients: Ca, Fe, Cu, Zn, vitamins….. some organisms need more than others

Microbial Life Runs Planet Earth Microbial diversity is vast. Number of species astronomical. <99.9% of microbial species have been cultured in the lab. Whole new uncultured lineages. Almost nothing known about them. Microbes: turn CO2 into organic matter most photosynthesis on the planet is done by prokaryotes then turn organic matter back into CO2 microbial metabolism is incredibly diverse

Aerobic Metabolisms (Aerobes) Animals “CH2O” + O2 ---> CO2 + H2O organotrophy Manganese Mn2+ + O2 ---> MnO4 (manganese oxide) chemotrophy Oxidizers Iron Fe2+ + O2 ---> Fe2O3 (iron oxide) chemotrophy Sulfide H2S + O2 ---> H2SO4 (sulfuric acid) chemotrophy Methane CH4 + O2 ---> CO2 + H2O chemotrophy Hydrogen 2H2 + O2 ---> 2H2O ??? Arsenic AsO3 (arsenite) + O2 ---> AsO4 (arsenate) chemotrophy

Anaerobic Metabolisms (Anaerobes) Sulfate H2SO4 + 4H2 ---> H2S + 4H2O chemotrophy Reducers Methanogenesis CO2 + 2H2 ---> CH4 + 2H2O chemotrophy Take home: -a lot of chemical reactions in the environment are catalyzed by microorganisms. -microbes can carry out some “unusual” reactions to make energy -energy generation results in constant oxidizing and reducing of compounds: sulfur, iron, manganese, carbon….. -called biogeochemical cycling.

The Importance of Oxygen Oxygen is a potent source of energy (strongest oxidant available) Anaerobic metabolisms don’t produce as much energy (ATP). Oxygen is also toxic - it is reactive. - causes damage to DNA - causes damage to proteins - causes damage to lipids - cells must be able to repair this damage

Extremophiles What is extreme for one organism is necessary for another. Organisms are all highly adapted to their niches.

Temperature Temperature One of the most important environmental factors that affect growth and survival of organisms. Too hot - proteins denature (think: fried egg - unfolded, coaggulated) Too cold - membranes and proteins freeze For every organism, there is a: minimum T optimal T (can be 4 or 105˚C) maximum T (remember water has to be liquid water) typical range of growth T is 30-40˚C

Growth Temperature Psychrophile - grows optimally below 15˚C 80% of Earth’s biosphere is < 15˚C. Mesophile - grows optimally between 15-45˚C Thermophile - grows optimally between 45-80˚C Hyperthermophiles - grows optimally above 80˚C ice core permanently frozen seawater McMurdo Sound Antarctica

Temperature Gradients 72˚C

pH Another environmental factor that affects growth and survival. pH is a logarithmic function so a change of 1 pH unit is a 10x change in [H+] Each organism has a pH range and a pH optimum. Most have a pH range of 2-3 units.

pH, cont. Most organisms grow optimally between pH 5-9. They are neutrophiles. Much fewer species can live outside of pH 5-9. Organisms that grow best below pH 5 are acidophiles. Organisms that grow best above pH 9 are alkaliphiles. pH 10 soda lake Lake Hamara, Egypt trona: Na2CO3 - habitat for halophilic, alkaliphilic archaea Acidic hot spring in Yellowstone National Park. Green: acidic eukaryotic algae

Water Activity Water activity is the availability of free water. Water can be loosely bound up by ions, proteins, clay minerals - this is NOT free water. hydration shell of ions in solution hydration shell of a protein Binding of free water reduces water activity in the environment.

Water Activity, cont. Water concentration (water activity) in salty environments is low. Water diffuses from high concentration --> low. Water diffuses from high water activity --> low. So, in a salty environment, free water diffuses out of the cell. Cells shrink and desiccate, proteins denature. Organisms must adapt to balance the water activity inside the cell with the water activity outside the cells. Salt Evaporation Ponds, San Francisco Bay Reddish purple: Halophilic Euryarchaeota

Halophiles Halophiles grow optimally at the water activity of seawater. 3% salt - halophile 1-6% salt - mild halophile 7-15% salt - moderate halophile 15-30% salt - extreme halophile Not very many species have adapted to these environments. Halotolerant organisms - grow best at low salt, but can tolerate short periods of elevated salt. Halogeometricum Square cells!

Lecture 19. Proterozoic Earth, Rise in Oxygen, Microbial Paleontology reading: Chapter 4