Streams draining mine tailings are extremely acidic—the effect of Thiobacillus ferrooxidans oxidizing sulfur and iron in pyrite minerals. What kind of bacteria are these?

-2

+4

+6

0

Photoautotrophs (PA) Chemoautotrophs(CA)

CH

Chemoheterotrophs (CH)

PA

The Sulfur cycle has many important effects on Aquatic Ecosystems

-1 pyrites(PA)

EnergyHOFeSOOHOFeS 8445.72 322

4222

Thiobacillus ferrooxidans oxidizes both the iron, Fe(+2) to Fe(+3)and the sulphur in the pyrites, S(-1) to S(+6) using molecular oxygen.

This reaction splits water to produce a great deal of acid.

How do you suggest that mine tailings should be stored?

Hydrothermal vent fauna: a community founded on Thiobacillus a chemoautotrophic bacteria

The pogonophoran tube worms harbour nodules of Thiobacillus inside their body cavities as mutualistic symbionts

Desulfovibrio : Sulfate reducing bacteriacommonly found in anaerobic aquatic environments with high levels of organic material, such as mud in lakes and ponds.•have metal reductases which can precipitate metal sulfides from the water—•bioremediation potentials for toxic radionuclides such as uranium by a reductive bioaccumulation process.

Sulfate reduction can absorb H+ and counteract acid rainThey also contribute to methylation of Mercury

Chemical equation for the oxidation of acetate by sulfate

Cper donated are 4

per accepted are 8

22

4)( (-2)6)( (0)

222

43

-

-

e

S e

COOHSHSOCOOCH

ECOOHSHSOCOOCH 22

243

Where do sulphate reducing bacteria fit in the functional classification?

http://www.esf.edu/efb/schulz/Limnology/Laboratory/PurpleBacteriafromGreenLake.JPG

Purple Photosynthetic sulfur bacteria (eg Thiocapsa)

•use reduced sulfur as an electron donor during photosynthesis. They are capable of oxidizing both sulfide and other reduced sulfur compounds.

Thiocapsa are found most often in fresh water: lakes, sulfur springs, and waste water ponds. Requires anoxic conditions with light present. Under ideal conditions, Thiocapsa can form dense blooms.

gas vacuoles. Why?

Chemical equation for anoxygenic photosynthesis in purple sulfur bacteria

Cper accepted 4

per donated are 2

612612

)0((0)4)( (-2)

2612622

-

-

e

S e

OHOHCSCOSH

OCHSenergylightCOSH 222

In aerobic photosynthesis O2 is produced. Why is no O2 produced here?

0 V

+0.25

-0.25

Earth’s crust, a reducing environment

Atmosphere, oxidizing environment

Soil layer

Redox profile at the earth’s surfaceThe earth is a 0.5 V battery

Photosynthesis--a strong photochemical redox reaction-- has produced a strong redox gradient across the earth’s surface.

This gradient helps maintain chemical diversity at the boundary Consider the example of soil N