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Lecture 18. Diversity of Microbial Life. What Do Microbes Need to Survive? Energy and
Metabolism. Extremophiles, Photosynthesis, and Chemosynthesis.
reading: Chapter 6
EXAM1:High: 88Low: 55Average: 72.2
Pervasiveness of Life
Snow algae on glacierSierra Nevada, CA
Earth life extraordinarily successfulNatural selection & evolution
--> adaptabilityOrganisms found EVERYWHERE
glaciers & permafrosthot springshydrothermal ventsdesert rockscloudsdeep sea sedimentssoils
Five Things You Need to Have Life
1. Stable Environmentbe able to adapt to changes
2. Liquid water-20˚C to 121˚C
3. Energy SourceO2 and carbohydratesoxidant (O2) and reductant (sugars)
4. Carbon Sourcecarbohydratessometimes different from an energy source
5. NutrientsThe Biogenic Elements: C, H, N, O, P, STrace Nutrients: Ca, Fe, Cu, Zn, vitamins…..some organisms need more than others
when considering thepotential for life elsewhere:
Liquid Water
If T below 0˚C, microbes can be foundgrowing 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.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Light Energy - photosynthesis phototrophconvert light energy into chemical energy (ATP)
Inorganic Compounds chemotroph, lithotrophneed an oxidant: O2, SO4
2- (sulfate), NO3- (nitrate), Fe3+
need a reductant: H2, H2S (sulfide), Fe2+, Mn2+
react oxidant and reductant, convert to ATP
Organic Compounds organotrophneed an oxidantorganic compounds as a reductant: glucose, cellulose
Energy Sources
Carbon Source
CO2 autotrophsorganic carbon heterotrophs
Can combine words for energy and carbon sources:
Name Energy Source Carbon Source
Photoheterotroph Light Organic C
Photoautotroph Light CO2
Chemoorganotroph Organic (reductant) and inorganic chemicals (oxidant)
Organic C
Chemoautotroph Inorganic chemicals (reductant & oxidant)
CO2
Also need NutrientsThe Biogenic Elements: C, H, N, O, P, STrace Nutrients: Ca, Fe, Cu, Zn, vitamins…..some organisms need more than others
Five Things You Need to Have Life
Microbial Life Runs Planet Earth
Sulfolobus
ThermofilumThermoproteus
pJP27pJP78
pSL22
pSL4
pSL50
pSL12Aquifex
ThermotogaThermomicrobium
Methanobacterium
ThermococcusMethanococcus
ARCHAEA
BACTERIA
EUCARYA
Thermus
EM17
Thermoplasma
OctSpA1-106
Methanothermus
OctSp92
Root
0.1 changes p er nucleotid e
Synechoccouschloroplasts
ClostridiumBacillus
CytophagaChlorobium
Agrobacterium
mitochondria
E. coliChromatium
Methanosarcina
Methanospirillum
Halobacterium
Marinemesophiles
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 mattermost photosynthesis on the planet is done by prokaryotesthen 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) chemotrophyOxidizers
Iron Fe2+ + O2 ---> Fe2O3 (iron oxide) chemotrophyOxidizers
Sulfide H2S + O2 ---> H2SO4 (sulfuric acid) chemotrophyOxidizers
Methane CH4 + O2 ---> CO2 + H2O chemotrophyOxidizers
Hydrogen 2H2 + O2 ---> 2H2O ???Oxidizers
Arsenic AsO3 (arsenite) + O2 ---> AsO4 (arsenate) chemotrophyOxidizers
Anaerobic Metabolisms (Anaerobes)
Sulfate H2SO4 + 4H2 ---> H2S + 4H2O chemotrophyReducers
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
TemperatureOne 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
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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˚C
ice corepermanently
frozen seawaterMcMurdo Sound
Antarctica
Temperature Gradients
72˚C
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.
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, Egypttrona: Na2CO3 - habitat for halophilic, alkaliphilic archaea
Acidic hot spring in YellowstoneNational 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 a protein hydration shell of ions in solution
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 grow optimally at the water activity of seawater.3% salt - halophile1-6% salt - mild halophile7-15% salt - moderate halophile15-30% 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.
Halophiles
HalogeometricumSquare cells!
Lecture 19. Proterozoic Earth, Rise in Oxygen, Microbial Paleontology
reading: Chapter 4
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