The purple phototrophic bacteria pdf free download

Chromatium sp. Hydrogen Energy 6: — Pfennig, N. Phototrophic green and purple bacteria: a comparative, systematic survey. The phototrophic bacteria. In: Buchanan, R. Bergey's manual of determinative bacteriology, 8th edn. Isolation of members of the families Chromatiaceae and Chlorobiaceae. In: Starr, M. The prokaryotes. A hand-book on habitats, isolation and identification of bacteria. Springer-Verlag, New York, p. Truper, H. Culture and isolation of phototrophic sulfur bacteria from the marine environment.

Characterization and identification of the anoxygenic phototrophic bacteria. Vethanayagam, R. Purple phototrophic bacteria from the mangrove environment. Download references. You can also search for this author in PubMed Google Scholar. Reprints and Permissions.

Purple photosynthetic bacteria from a tropical mangrove environment. Download citation. Accepted : 09 April They take H to become reduced they give H to become oxidized. Cytochrome and Fe-S proteins give and take electrons. Therefore, they are known as electron carriers of the ETC. Flavoproteins and quinones give and take H for oxidation and reduction. Therefore, they are called H carriers of the electron transport chain. Transport of electrons help the translocation of protons from one side of the membrane to the other side of the membrane.

There are several mechanisms of proton translocation whatever the mechanism the protons translocation creates a proton concentration difference across the membrane.

The concentration difference of protons gives a potential energy difference across the membrane. The charge difference and the PH difference together gives this difference in potential energy. Membranes have ATP synthase embedded within a part of the enzyme structure comes out from the membrane and that can be seen as white spots on the inner side of the inner mitochondrial membrane. The 3D structure of the ATP synthase protein has a cavity in the part of the enzyme that comes out from the membrane.

This cavity has binding sites for ADP and phosphate groups. Photosynthetic Membranes, Chloroplasts, and Chlorosomes The chlorophyll pigments and all the other components of the light-gathering apparatus exist within membranes in the cell. The location of these photosynthetic membranes differs between prokaryotic and eukaryotic microorganisms. In eukaryotic phototrophs, photosynthesis takes place in intracellular organelles, the chloroplasts, where the chlorophylls are attached to sheet-like membranes These photosynthetic membrane systems are called thylakoids, and stacks of thylakoids form grana.

This arrangement makes possible the generation of a light-driven proton motive force that is used to synthesize ATP. Chloroplasts are absent from prokaryotic phototrophs.

In purple bacteria, the photosynthetic pigments are integrated into internal membrane systems that arise from invagination of the cytoplasmic membrane.

Membrane vesicles called chromatophores or membrane stacks called lamellae are common membrane arrangements in purple bacteria. In cyanobacteria, photosynthetic pigments reside in lamellar membranes also called thylakoids because of their resemblance to the thylakoids in the chloroplasts of algae.

The ultimate structure for capturing low light intensities is the chlorosome. Chlorosomes are present in the anoxygenic green sulfur bacteria and green nonsulfur bacteria. Chlorosomes function as giant antenna systems, but unlike the antennae of purple bacteria or cyanobacteria, bacteriochlorophyll molecules in the chlorosome are not attached to proteins.

Chlorosomes contain bacteriochlorophyll c, d, or e arranged in dense arrays running along the long axis of the structure. Light energy absorbed by these antenna pigments is transferred to bacteriochlorophyll an in the reaction center in the cytoplasmic membrane through a small protein called the FMO protein. Green bacteria can grow at the lowest light intensities of all known phototrophs and are often found in the deepest waters of lakes, inland seas, and other anoxic aquatic habitats where light levels are too low to support other phototrophs.

Green nonsulfur bacteria are major components of microbial mats, thick biofilms that form in hot springs and highly saline environments. Microbial mats experience a steep light gradient, with light levels even a few millimeters into the mat approaching darkness. Hence, chlorosomes allow green nonsulfur bacteria to grow phototrophically with only the minimal light intensities available. These pigments include, in particular, the carotenoids and phycobilins.

Carotenoids — The most widespread accessory pigments in phototrophs are the carotenoids. Carotenoids are hydrophobic pigments that are firmly embedded in the photosynthetic membrane. Carotenoids are typically yellow, red, brown, or green and absorb light in the blue region of the spectrum.

Because they tend to mask the color of bacteriochlorophylls, carotenoids are responsible for the brilliant colors of red, purple, pink, green, yellow, or brown that are observed in different species of anoxygenic phototrophs. Carotenoids are closely associated with chlorophyll or bacteriochlorophyll in photosynthetic complexes, and some of the energy absorbed by carotenoids can be transferred to the reaction center. However, carotenoids function primarily as photo protective agents.

Bright light can be harmful to cells because it can catalyze photo oxidation reactions that can produce toxic forms of oxygen, such as singlet oxygen 1O2. Carotenoids quench toxic oxygen species by absorbing much of this harmful light and in this way prevent these dangerous photo oxidations. Because phototrophic organisms by their very nature must live in the light, the photo protection conferred by carotenoids is clearly advantageous.

Phycobiliproteins and Phycobilisomes Cyanobacteria and the chloroplasts of red algae which are descendants of cyanobacteria, contain pigments called phycobiliproteins, which are the main light-harvesting systems of these phototrophs.

Phycobiliproteins consist of red or blue-green linear tetrapyrroles, called bilins, bound to proteins, and give cyanobacteria and red algae their characteristic colors. The red phycobiliprotein, called phycoerythrin, absorbs most strongly at wavelengths around nm, whereas the blue phycobiliprotein, phycocyanin, absorbs most strongly at nm. A third phycobiliprotein, called allophycocyanin, absorbs at about nm.

Phycobiliproteins assemble into aggregates called phycobilisomes that attach to cyanobacterial thylakoids. Phycobilisomes are arranged such that the allophycocyanin molecules are in direct contact with the photosynthetic membrane.

Allophycocyanin is surrounded by phycocyanin or phycoerythrin or both, depending on the organism. Phycocyanin and phycoerythrin absorb light of shorter wavelengths higher energy and transfer some energy to allophycocyanin, which is positioned closest to the reaction center chlorophyll and transfers energy to it. Phycobilisomes facilitate energy transfer to cyanobacterial reaction centers, allowing cyanobacteria to grow at lower light intensities than would otherwise be possible.

Photophosphorelatory electron transport chain begins with chemicals with law reduction potential. As it is very low the third member of the ETC is unable to take electrons unless there are free electrons available. It cannot Ex. Light energy mainly solar energy helps photophosphorelatory organisms to give a free electron to the ETC. What happens is that photosynthetic pigments release electrons under light energy.

Mg is the active center of these pigments and due to the chemical nature of chlorophyll molecules, electrons are ejected from Mg under the energy of light. The low reduction potential of the first member of ETC is illustrated in the graph usually drawn to describe photophosphorylation. The reduction potential of each member of the ETC is given along the y axis of the graph.

The top of the y axis is for very low reduction potential values. That is a large negative value. The first member of ETC is therefore, put on the top of the y axis.

Once the first member takes the free electrons, that electrons will be transported along the electron transport chain. As a result, proton translocation takes place, proton motive force will be establishing and ATP is synthesized by ATP synthase enzyme. The electron will take a cyclic path and come back to the chlorophyll molecule. This brings a chlorophyll molecule back to its normal state and the ATP synthesis can be continued.

There is a large number of such reduction reactions taking place in cells and those reactions are supported by NADH and such Co — enzymes.

Wesley D. Swingley, Robert E. Blankenship, Jason Raymond. New Light on Aerobic Anoxygenic Phototrophs. Biosynthesis of Bacteriochlorophylls in Purple Bacteria. Distribution and Biosynthesis of Carotenoids. Membrane Lipid Biosynthesis in Purple Bacteria. Peripheral Complexes of Purple Bacteria. Mads Gabrielsen, Alastair T. Gardiner, Richard J. Per A. Bullough, Pu Qian, C. Neil Hunter. Energy Transfer from Carotenoids to Bacteriochlorophylls.

Rienk van Grondelle, Vladimir I. Page 1 Navigate to page number of 3. About this book Introduction The Purple Phototrophic Bacteria is a comprehensive survey of all aspects of these fascinating bacteria, the metabolically most versatile organisms on Earth.