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Purple bacteria

 

 
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Purple bacteria
 
 
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Purple bacteria or purple photosynthetic bacteria are 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....
 that are phototroph
Phototroph

Photoautotrophs or Phototroph are organisms that carry out photosynthesis to acquire energy. Energy from light, carbon dioxide and water are converted into organic materials to be used in cell functions such as biosynthesis and Cellular respiration....
ic, i.e. capable of producing energy through 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....
. They are pigmented with bacteriochlorophyll
Bacteriochlorophyll

Bacteriochlorophylls are photosynthetic pigments that occur in various phototrophic bacterium. They are related to chlorophylls, which are the primary pigments in plants, algae, and cyanobacteria....
 a or b, together with various carotenoid
Carotenoid

Carotenoids are organic compound pigments that are naturally occurring in chromoplasts of plants and some other photosynthesis organisms like algae, some types of fungus and some bacterium....
s. These give them colours ranging between purple, red, brown, and orange. Photosynthesis takes place at reaction centers on the cell membrane
Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
, which is folded into the cell to form sacs, tubes, or sheets, increasing the available surface area.

Like most other photosynthetic bacteria, purple bacteria 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]]...
, because the 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....
 involved in photosynthesis is not water.






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Purple bacteria or purple photosynthetic bacteria are 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....
 that are phototroph
Phototroph

Photoautotrophs or Phototroph are organisms that carry out photosynthesis to acquire energy. Energy from light, carbon dioxide and water are converted into organic materials to be used in cell functions such as biosynthesis and Cellular respiration....
ic, i.e. capable of producing energy through 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....
. They are pigmented with bacteriochlorophyll
Bacteriochlorophyll

Bacteriochlorophylls are photosynthetic pigments that occur in various phototrophic bacterium. They are related to chlorophylls, which are the primary pigments in plants, algae, and cyanobacteria....
 a or b, together with various carotenoid
Carotenoid

Carotenoids are organic compound pigments that are naturally occurring in chromoplasts of plants and some other photosynthesis organisms like algae, some types of fungus and some bacterium....
s. These give them colours ranging between purple, red, brown, and orange. Photosynthesis takes place at reaction centers on the cell membrane
Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
, which is folded into the cell to form sacs, tubes, or sheets, increasing the available surface area.

Like most other photosynthetic bacteria, purple bacteria 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]]...
, because the 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....
 involved in photosynthesis is not water. In some, called purple sulfur bacteria
Purple sulfur bacteria

The purple sulfur bacteria are a group of Proteobacteria capable of photosynthesis, collectively referred to as purple bacteria. They are Anaerobic organism or microaerophilic, and are often found in hot springs or stagnant water....
, it is either sulfide
Sulfide

The term sulfide refers to several types of chemical compounds containing sulfur in its lowest oxidation number of −2.Formally, "sulfide" is the dianion, S2−, which exists in strongly alkaline aqueous solutions formed from H2S or alkali metal salts such as Li2S, Na2S, and K2...
 or 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....
. The others, called purple non-sulfur bacteria (aka PNSB), typically use hydrogen
Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
 although some may use other compounds in small amounts. At one point these were considered families, but RNA trees show the purple bacteria make up a variety of separate groups, each closer relatives of non-photosynthetic proteobacteria than one another.

Purple non-sulfur bacteria are found among the alpha and beta subgroups, including:
Rhodospirillales
Rhodospirillales

The Rhodospirillales are an order of proteobacteria, with two families. The Acetobacteraceae comprise the acetic acid bacteria, which are heterotrophism and produce acetic acid during their respiration....
     Rhodospirillaceae
Rhodospirillaceae

The Rhodospirillaceae are a family of Proteobacteria. The majority are purple bacteria, producing energy through photosynthesis; originally all purple non-sulfur bacteria were include here....
 		 e.g. Rhodospirillum
     Acetobacteraceae e.g. Rhodopila
Rhizobiales
Rhizobiales

Rhizobiales is an Order of alpha proteobacteria. The rhizobia, which nitrogen fixation and are symbiotic with plant roots, appear in several different families here....
     Bradyrhizobiaceae
Bradyrhizobiaceae

The Bradyrhizobiaceae are a family of bacterium, with ten genera. They include plant-associated bacteria such as Bradyrhizobium, a genus of rhizobia associated with some legumes....
 		 e.g. Rhodopseudomonas
     Hyphomicrobiaceae
Hyphomicrobiaceae

The Hyphomicrobiaceae are a family of bacterium. Among others, they include Azorhizobium, a genus of rhizobia, and Rhodomicrobium, a genus of purple bacteria....
 		 e.g. Rhodomicrobium
     Rhodobiaceae e.g. Rhodobium
Rhodobium (bacterium)

Rhodobium is a genus of purple bacteria that reproduces by budding. The cells are rod-shaped and reproduce by budding, as in many other members of the Rhizobiales....
Other families
     Rhodobacteraceae
Rhodobacteraceae

The Rhodobacteraceae are a family of proteobacteria, given their own order within the alpha subgroup.In alpha taxonomy, the Rhodobacteraceae are a family of the Rhodobacterales....
 		 e.g. Rhodobacter
Rhodobacter

In alpha taxonomy, Rhodobacter is a genus of the Rhodobacteraceae.The most famous species of Rhodobacter is Rhodobacter sphaeroides, which is commonly used to express proteins....
     Rhodocyclaceae
Rhodocyclaceae

The Rhodocyclaceae are a family of gram-negative bacterium. They are given their own order in the beta subgroup of Proteobacteria, and include many genera previously assigned to the family Pseudomonadaceae....
 		 e.g. Rhodocyclus
     Comamonadaceae
Comamonadaceae

The Comamonadaceae are a family of Proteobacteria.es:Comamonadaceaefr:Comamonadaceae...
 		 e.g. Rhodoferax
Purple 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....
 bacteria are included among the gamma subgroup, and make up the order Chromatiales
Purple sulfur bacteria

The purple sulfur bacteria are a group of Proteobacteria capable of photosynthesis, collectively referred to as purple bacteria. They are Anaerobic organism or microaerophilic, and are often found in hot springs or stagnant water....
. The similarity between the photosynthetic machinery in these different lines indicates it had a common origin, either from some common ancestor or passed by lateral transfer.

Purple bacteria were the first bacteria discovered to photosynthesize without having an oxygen byproduct. Instead, their byproduct is sulfur. This was proved by first establishing the bacteria's reactions to different concentrations of oxygen. What was found was that the bacteria moved quickly away from even the slightest trace of oxygen. Then a dish of the bacteria was taken, and a light was focused on one part of the dish leaving the rest dark. As the bacteria cannot survive without light, all the bacteria moved into the circle of light, becoming very crowded. If the bacteria's byproduct was oxygen, the distances between individuals would become larger and larger as more oxygen was produced. But because of the bacteria's behavior in the focused light, it was concluded that the bacteria's photosynthetic byproduct could not be oxygen.