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Purple sulfur bacteria

 
Purple Sulfur Bacteria

 
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Purple sulfur bacteria
 
 
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The purple sulfur bacteria are a group of Proteobacteria
Proteobacteria

The Proteobacteria are a major group of bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera....
 capable of photosynthesis
Photosynthesis

File:Seawifs global biosphere.jpgPhotosynthesis is a metabolic pathway that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight....
, collectively referred to as purple bacteria
Purple bacteria

Purple bacteria or purple photosynthetic bacteria are proteobacteria that are phototrophic, i.e. capable of producing energy through photosynthesis....
. They are anaerobic
Anaerobic organism

An anaerobic organism is any organism that does not require oxygen for growth and may even die in its presence....
 or microaerophilic, and are often found in hot spring
Hot spring

A hot spring is a Spring that is produced by the emergence of Geothermal groundwater from the earth's crust . There are hot springs all over the earth, on every continent and even under the oceans and seas....
s or stagnant water. Unlike plants , algae
Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds....
, and cyanobacteria
Cyanobacteria

Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis....
, they do not use water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
 as their reducing agent
Reducing agent

A reducing agent is the element or compound in a redox reaction that reduces another Chemical species. In doing so, it becomes oxidized, and is therefore the electron donor in the redox....
, and so do not produce oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
. Instead they use hydrogen sulfide
Hydrogen sulfide

Hydrogen sulfide is the chemical compound with the chemical formula Hydrogen2Sulfur. This colorless, toxic and flammable gas is partially responsible for the foul odor of egg and flatulence....
, which is oxidized to produce granules of elemental sulfur
Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
. This in turn may be oxidized to form sulfuric acid
Sulfuric acid

Sulfuric acid, hydrogen2sulfuroxygen4, is a strong mineral acid. It is soluble in water at all concentrations. Sulfuric acid has many applications, and is one of the top products of the chemical industry....
.

The purple sulfur bacteria are divided into two families, the Chromatiaceae
Chromatiaceae

The Chromatiaceae are the main family of purple sulfur bacteria. They are distinguished by producing sulfur globules within their cells. These are an intermediate in the oxidization of sulfide, which is ultimately converted into sulfate, and may serve as a reserve....
 and Ectothiorhodospiraceae
Ectothiorhodospiraceae

The Ectothiorhodospiraceae are a family of purple sulfur bacteria, distinguished by producing sulfur globules outside of their cells. They are generally marine....
, which respectively produce internal and external sulfur granules, and show differences in the structure of their internal membranes.






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Encyclopedia


The purple sulfur bacteria are a group of Proteobacteria
Proteobacteria

The Proteobacteria are a major group of bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera....
 capable of photosynthesis
Photosynthesis

File:Seawifs global biosphere.jpgPhotosynthesis is a metabolic pathway that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight....
, collectively referred to as purple bacteria
Purple bacteria

Purple bacteria or purple photosynthetic bacteria are proteobacteria that are phototrophic, i.e. capable of producing energy through photosynthesis....
. They are anaerobic
Anaerobic organism

An anaerobic organism is any organism that does not require oxygen for growth and may even die in its presence....
 or microaerophilic, and are often found in hot spring
Hot spring

A hot spring is a Spring that is produced by the emergence of Geothermal groundwater from the earth's crust . There are hot springs all over the earth, on every continent and even under the oceans and seas....
s or stagnant water. Unlike plants , algae
Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds....
, and cyanobacteria
Cyanobacteria

Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis....
, they do not use water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
 as their reducing agent
Reducing agent

A reducing agent is the element or compound in a redox reaction that reduces another Chemical species. In doing so, it becomes oxidized, and is therefore the electron donor in the redox....
, and so do not produce oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
. Instead they use hydrogen sulfide
Hydrogen sulfide

Hydrogen sulfide is the chemical compound with the chemical formula Hydrogen2Sulfur. This colorless, toxic and flammable gas is partially responsible for the foul odor of egg and flatulence....
, which is oxidized to produce granules of elemental sulfur
Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
. This in turn may be oxidized to form sulfuric acid
Sulfuric acid

Sulfuric acid, hydrogen2sulfuroxygen4, is a strong mineral acid. It is soluble in water at all concentrations. Sulfuric acid has many applications, and is one of the top products of the chemical industry....
.

The purple sulfur bacteria are divided into two families, the Chromatiaceae
Chromatiaceae

The Chromatiaceae are the main family of purple sulfur bacteria. They are distinguished by producing sulfur globules within their cells. These are an intermediate in the oxidization of sulfide, which is ultimately converted into sulfate, and may serve as a reserve....
 and Ectothiorhodospiraceae
Ectothiorhodospiraceae

The Ectothiorhodospiraceae are a family of purple sulfur bacteria, distinguished by producing sulfur globules outside of their cells. They are generally marine....
, which respectively produce internal and external sulfur granules, and show differences in the structure of their internal membranes. They make up the order Chromatiales, included in the gamma subdivision of the Proteobacteria. The genus Halothiobacillus
Halothiobacillus

Halothiobacillus is a genus of Proteobacteria. The members of this genus used to belong to Thiobacillus, before they were reclassified in the year 2000....
 is also included in the Chromatiales, in its own family, but it is not photosynthetic.

Purple sulfur bacteria are generally found in illuminated anoxic zones of lakes and other aquatic habitats where hydrogen sulfide accumulates and also in "sulfur springs" where geochemically or biologically produced hydrogen sulfide can trigger the formation of blooms of purple sulfur bacteria. Anoxic conditions are required for photosynthesis; these bacteria cannot thrive in oxygenated environments.

The most favorable lakes for the development of purple sulfur bacteria are meromictic
Meromictic

A meromictic lake has layers of water which do not intermix. In ordinary, "holomictic" lakes, at least once each year there is a physical mixing of the surface and the deep waters....
 (permanently stratified) lakes. Meromictic lakes stratify because they have denser (usually saline) water in the bottom and less dense (usually freshwater) nearer the surface. If sufficient sulfate is present to support sulfate reduction, the sulfide, produced in the sediments, diffuses upward into the anoxic bottom waters, and here purple sulfur bacteria can form dense cell masses, called blooms, usually in association with green phototrophic bacteria.

See also

  • Sulfur-reducing bacteria
    Sulfur-reducing bacteria

    Sulfur-reducing bacteria get their energy by reducing elemental sulfur to hydrogen sulfide. They couple this reaction with the oxidation of acetate, succinate or other organic compounds....
  • Green Lake (New York)
    Green Lake (New York)

    Green Lake is the larger of the two lakes in Green Lakes State Park just east of Syracuse, New York in Onondaga County, New York; Round Lake National Natural Landmark is the smaller lake located west of Green Lake....
  • Anoxic event
    Anoxic event

    Oceanic anoxic events or anoxic events occur when the Earth's oceans become completely depleted of oxygen below the surface levels. Although anoxic events have not happened for millions of years, the geological record shows that they happened many times in the past....
  • Anoxygenic photosynthesis