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

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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