Presentation on theme: "Lecture 18. Diversity of Microbial Life"— Presentation transcript:
1 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: 88Low: 55Average: 72.2reading: Chapter 6
2 Pervasiveness of Life Earth life extraordinarily successful Natural selection & evolution--> adaptabilityOrganisms found EVERYWHEREglaciers & permafrosthot springshydrothermal ventsdesert rockscloudsdeep sea sedimentssoilsSnow algae on glacierSierra Nevada, CA
3 Five Things You Need to Have Life Stable Environmentbe able to adapt to changesLiquid water-20˚C to 121˚CEnergy SourceO2 and carbohydratesoxidant (O2) and reductant (sugars)Carbon Sourcecarbohydratessometimes different from an energy sourceNutrientsThe Biogenic Elements: C, H, N, O, P, STrace Nutrients: Ca, Fe, Cu, Zn, vitamins…..some organisms need more than otherswhen considering thepotential for life elsewhere:
4 Liquid Water If T below 0˚C, microbes can be found growing between ice crystals or in thepore spaces of ice.Microbes can secrete compounds that caninhibit ice crystal formation.Soil still contains substantial thin films ofliquid water below 0˚C… could be important for life on Mars.
5 Energy Sources Light Energy - photosynthesis phototroph convert light energy into chemical energy (ATP)Inorganic Compounds chemotroph, lithotrophneed an oxidant: O2, SO42- (sulfate), NO3- (nitrate), Fe3+need a reductant: H2, H2S (sulfide), Fe2+, Mn2+react oxidant and reductant, convert to ATPOrganic Compounds organotrophneed an oxidantorganic compounds as a reductant: glucose, cellulose
6 Carbon Source CO2 autotrophs organic carbon heterotrophs Can combine words for energy and carbon sources:NameEnergy SourceCarbon SourcePhotoheterotrophLightOrganic CPhotoautotrophCO2ChemoorganotrophOrganic (reductant) and inorganic chemicals (oxidant)ChemoautotrophInorganic chemicals (reductant & oxidant)
7 Five Things You Need to Have Life Also need NutrientsThe Biogenic Elements: C, H, N, O, P, STrace Nutrients: Ca, Fe, Cu, Zn, vitamins…..some organisms need more than others
8 Microbial Life Runs Planet Earth Microbial diversity is vast.Number of species astronomical.<99.9% of microbial species havebeen cultured in the lab.Whole new uncultured lineages.Almost nothing known about them.Microbes:turn CO2 into organic mattermost photosynthesis on theplanet is done by prokaryotesthen turn organic matter backinto CO2microbial metabolism is incrediblydiverse
9 Aerobic Metabolisms (Aerobes) Animals “CH2O” O > CO H2O organotrophyManganese Mn O > MnO4 (manganese oxide) chemotrophyOxidizersIron Fe O > Fe2O3 (iron oxide) chemotrophySulfide H2S O > H2SO4 (sulfuric acid) chemotrophyMethane CH O > CO H2O chemotrophyHydrogen 2H O > 2H2O ???Arsenic AsO3 (arsenite) + O > AsO4 (arsenate) chemotrophy
10 Anaerobic Metabolisms (Anaerobes) Sulfate H2SO H > H2S H2O chemotrophyReducersMethanogenesis CO H > CH H2O chemotrophyTake home:-a lot of chemical reactions in the environment are catalyzedby microorganisms.-microbes can carry out some “unusual” reactions to make energy-energy generation results in constant oxidizing and reducing ofcompounds: sulfur, iron, manganese, carbon…..-called biogeochemical cycling.
11 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
12 ExtremophilesWhat is extreme for one organism is necessary for another.Organisms are all highly adapted to their niches.
13 Temperature Temperature One of the most important environmental factors thataffect growth and survival of organisms.Too hot - proteins denature (think: fried egg - unfolded, coaggulated)Too cold - membranes and proteins freezeFor every organism, there is a:minimum Toptimal 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
14 Growth Temperature Psychrophile - grows optimally below 15˚C 80% of Earth’s biosphere is < 15˚C.Mesophile - grows optimally between 15-45˚CThermophile - grows optimally between 45-80˚CHyperthermophiles - grows optimally above 80˚Cice corepermanentlyfrozen seawaterMcMurdo SoundAntarctica
16 pH Another environmental factor that affects growth and survival. pH is a logarithmic function so achange of 1 pH unit is a 10x changein [H+]Each organism has a pH range anda pH optimum.Most have a pH range of 2-3units.
17 pH, cont.Most organisms grow optimally between pH 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, Egypttrona: Na2CO3 - habitat for halophilic, alkaliphilic archaeaAcidic hot spring in YellowstoneNational Park. Green: acidic eukaryotic algae
18 Water Activity Water activity is the availability of free water. Water can be loosely bound up by ions, proteins, clay minerals - thisis NOT free water.hydration shell of ions in solutionhydration shell of a proteinBinding of free water reduces water activity in the environment.
19 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 withthe water activity outside the cells.Salt Evaporation Ponds,San Francisco BayReddish purple: Halophilic Euryarchaeota
20 HalophilesHalophiles grow optimally at the water activity of seawater.3% salt - halophile1-6% salt - mild halophile7-15% salt - moderate halophile15-30% salt - extreme halophileNot very many species have adapted to these environments.Halotolerant organisms - grow best at low salt, but can tolerateshort periods of elevated salt.HalogeometricumSquare cells!