Purple sulfur bacteria

Bacteriochlorophyll- Light-absorbing pigment found in green sulfur and purple sulfur bacteria. 

In photosynthetic bacteria, HgA is variously HaS (photosynthetic green and purple sulfur bacteria), isopropanol, or some similar oxidizable substrate. [(CH2O) symbolizes a carbohydrate unit.]... 

Purple sulfur bacteria fix carbon dioxide using the Calvin-Benson cycle, but green sulfur bacteria use a completely different pathway, the reverse tricarboxylic acid cycle. Other photosynthetic bacteria use still different pathways for CO2 fixation (Perry and Staley, 1997). 

Bacteriochlorophyll b 368, 795" Purple sulfur bacteria Brown-pink -C0CH3 -CH3 =CHCH3 -CH CHjCOO-phytyl Single Single... 

A study of photosynthetic organisms other than green plants has revealed that certain bacteria, such as the purple sulfur bacteria, utilize H2S instead of H20 as a reductant in photosynthesis. The product obtained is elemental sulfur instead of oxygen ... 

It should be recalled that for purple sulfur bacteria the equation is [Eq. (12.2)]... 

Aside from C. vinosum, type III-PHA synthases have so far been detected exclusively in the phototrophic purple sulfur bacteria such as Thiocystis viol-acea [51] and Thiocapsa pfennigii [26, 57] and in cyanobacteria such as Synechocystis sp. PCC6803 [49] or Synechococcus sp. MAI 9 [58]. In contrast, the photosynthetic nonsulfur purple bacteria possess type I-PHA synthases. 

Role of H2S in Some Photosynthetic Bacteria Illuminated purple sulfur bacteria carry out photosynthesis in the presence of H20 and 14C02, but only if H2S is added and 02 is absent. During the course of photosynthesis, measured by formation of [14C]carbohydrate, H2S is converted to elemental sulfur, but no 02 is evolved. What is the role of the conversion of H2S to sulfur Why is no 02 evolved ... 

Anoxygenic photosynthetic bacteria. Green sulfur bacteria. Chlorobium, Prosthecochloris purple nonsulfur bacteria Rhodopseudomonas, Rhodospirillum purple sulfur bacteria Chromatium, Thiospirillum... 

V). The centers resemble PSII of chloroplasts and have a high midpoint electrode potential E° of 0.46 V. The initial electron acceptor is the Mg2+-free bacteriopheophytin (see Fig. 23-20) whose midpoint potential is -0.7 V. Electrons flow from reduced bacteriopheophytin to menaquinone or ubiquinone or both via a cytochrome bct complex, similar to that of mitochondria, then back to the reaction center P870. This is primarily a cyclic process coupled to ATP synthesis. Needed reducing equivalents can be formed by ATP-driven reverse electron transport involving electrons removed from succinate. Similarly, the purple sulfur bacteria can use electrons from H2S. 

Bacteriochlorophyll a is the dominant light-harvesting pigment in purple sulfur bacteria (e.g., Chromatiaceae) and where its synthesis is inhibited by the presence of O2. Similarly, bacteriochlorophyll e has been shown to be indicative of green sulfur bacteria (e.g., Chlorobium phaeovibroides and... 

Jprgensen, B.B., and Des Marais, D.J. (1986) Competition for sulfide among colorless and purple sulfur bacteria in cyanobacterial mats. FEMS Microbiol. Ecol. 38, 179-186. 

Answer Purple sulfur bacteria use H2S as a source of electrons and protons ... 

Fig. 3. Light-driven electron transport pathways in purple bacteria and in filamentous bacteria. Boxed-in components are membrane-bound. Secondary electron acceptors (MQ and UQ) in RCs are placed according to their effective midpoint potentials (without proton exchanges). Dashed pathways have not yet been demonstrated. The pathway from S to P-870 or P-970 is found only in purple sulfur bacteria.

Little is known about the electron flow pathways when Chloroflexus oxidizes to S° and fixes CO2, but it seems reasonable to suppose that NAD is reduced by reverse electron flow from the MQ pool in analogy to the mechanism used by the purple sulfur bacteria (Chapter 9). 

Purple sulfur bacteria Amoebobacter Chromatium Ectothiorhodospira Lamprocystis Thiocapsa Thiocystis Thiodictyon Thiopedia Thiospirillum Unicellular rods, spheres, spirals... 

Many photosynthetic purple bacteria are closely related phylogenetically to nonphotosynthetic respiring eubacteria. Some photosynthetic eubacteria are autotrophic (e.g. green and purple sulfur bacteria), while others are mainly hetero-trophic (e.g. filamentous bacteria, purple non-sulfur bacteria and H. chlorum). All convert light energy into chemical free energy. 

The pathway(s) for thiosulfate oxidation in purple sulfur bacteria are poorly understood, with both a membrane-bound c cytochrome [113] and a soluble iron-sulfur protein [114] having been proposed as possible acceptors of electrons arising from thiosulfate oxidation. However, it is known that in C. vinosum electrons from thiosulfate can be used to reduce NAD(P) in an uncoupler-sensitive reaction (vide... 

Other unique sites of N2 fixation remain to be discovered. Dense populations of Archaea are also found throughout the water column of the worlds oceans (DeLong, 1992 Fuhrman et al., 1992), and some methanogens have the capacity for diazotrophy (Murray and Zinder, 1984). Indeed, diazotrophic archaeal nijH sequences have been obtained from a marine vent community and in deep sea waters away from vents (Mehta et al., 2003, 2005). They also obtained an isolate capable of growth and N2 fixation up to 92°C (Mehta and Baross, 2006). N2 fixing bacteria, including purple sulfur bacteria, are also associated with the intestinal flora of zooplankton (Braun etal., 1999 Proctor, 1997). 

Many phototrophs do not produce O2 as a waste product. Such anoxygenic phototrophs are comprised of purple sulfur, purple nonsulfur, green sulfur, and green nonsulfur bacteria. Although purple sulfur bacteria are typically found in anoxic zones of lakes and sediments, many are capable of photosynthesis under oxic conditions (Van Gemer-den, 1993). Most fix N2 and store S° intra- or extracellularly, and some are capable of chemo-lithoautotrophic growth. Extreme halophilic, sulfi-dic, and mildly thermophilic environments harbor... 

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