Photosynthetic bacteria Chromatium

Weaver, P., K. Tinker, and R. C. Valentine Ferredoxin linked DPN reduction by the photosynthetic bacteria Chromatium and Chlorobium. Biochem. Biophys. Res. Commun, 27, 195—201 (1965). 

In order to obtain pure cultures, the crude culture which contained Chromatium species was serially diluted in this modified medium as suggested by van Niel ( 1). This was repeated several times to ensure the purity of the culture. The agar shake method was not used as the large photosynthetic bacteria fail to grow in agar shake tubes ( 1). In pure culture the Chromatium species did not grow as well as in the mixed culture situation. The culture was not as dense or as rich in colour as the crude cultures. 

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

The role of ferredoxin in reactions of photosynthetic bacteria is summarized in Fig. 11. Reactions which should now be possible to show, but so far have not been observed in cell-free systems, are the fcrredoxin-dependent photoproduction of hydrogen gas and photoreduction of pyridine nucleotide. Hood (56) reported a two-fold stimulation by ferredoxin in the photoreduction of DPN by chlorophyll-containing particles from Chromatium. Hood s results were inconsistent and Hinkson (54) found that the ferredoxin requirement is not specific and may be satisfied by serum albumin. In addition, there is still no evidence for a role of ferredoxin in photophosphorylation by photosynthetic bacteria, similar to that in chloroplasts. 

Another experimental approach to the study of sulfureta in sediments was devised by Hallberg et al. (1976). Closed plexiglass boxes (Schippel et al., 1973) equipped with sampling ports and electrodes for continuous measurement of pH, Eh and sulfide-ion activity are anchored in soft bottom sediments, and physical, chemical and biological characteristics of the sediment-water system monitored over a period of time. In a 9-month experiment on Baltic Sea sediments, sulfate reduction proceeded rapidly in the early stages followed by sulfide reoxidation due to the development of the photosynthetic sulfur bacteria Chromatium and Chlorobium. 

The pH at which the line with a -60 mV/pH slope intersects that with 0 m V/pH slope represents the pK value of reduced Qa. which, as noted, is 9.6. A similar midpoint potential-pH dependence has been reported for Chromatium vinosum, Rs. rubrum and Rp. viridis, with pK values of 8.0, 8.8 and 7.8 respectively. Interestingly, the equilibrium midpoint potentials for the chromatophores of these four different photosynthetic bacteria estimated from the point of intersection ofthe lines of 60 and 0 mV/pH slopes are rather similar, lying within a narrow 50 mV range centered at -175 mV. 

Subsequently Halsey and Parson pursued this issue further by removing ubiquinone from Chromatium chromatophores and examining the consequences. The authors found that while the extracted chromato-phores were photochemically active on the first flash, they lost the ability entirely to perform photochemistry on the second flash, even when delayed by several seconds after the first. Reconstitution of the extracted chromatophores with the Mpid extracts restored the photochemical activity. Taking these results together with the chemical identity ofthe extracts allowed these workers to conclude that ubiquinone serves as the secondary electron acceptor, Qb, in such photosynthetic bacteria as Chromatium and Rb. sphaeroides. 

The second kind of reaction center, as represented by that of Chromatium vinosum or Rhodopseudo-monas viridis, has a tightly bound c-type cytochrome [see Fig. 2, right]. This so-called reaction center-associated cytochrome is a tetraheme of molecular mass of 40 kDa and structurally quite different from the other known, c-type cytochromes. One of the hemes in this RC-associated, c-type cytochrome also serves as the immediate electron donor to the photooxidized primary donor of the photosynthetic bacteria (either P870 in C. vinosum or P960 in Rp. viridis). The oxidized cytochrome in the tetraheme is in turn reduced by the soluble cytochrome C2. The RC-associated cytochromes are not easily dissociated from the RC, even at high ionic strength. 

In some early studies of cytochrome reactions in photosynthetic bacteria. Chance and Nishimura made a remarkable observation with regard to the temperature dependence of photooxidation of the c-type cytochromes in photosynthetic bacteria. They found that in Chromatium the low-potential Cyt c553 (also called Cyt c423.5 according to the wavelength of the Soret band) can still undergo photooxidation at low temperatures. Fig. 5 shows that the oxidation rate of Chromatium Cyt c is about the same at 300 as at 250 K, while the rate of re-reduction is deaeased about 6-fold. What is remarkable is that at 77 K the rate of cytochrome oxidation appears to be even faster than at ambient temperature. The oxidized... 

On the other hand, carotenoids in light-harvesting complexes of photosynthetic bacteria assume an all-trans configuration, either twisted (as in Rs. rubrum, Chromatium vinosum, md Rp. palustris) or planar (as in Rb. sphaeroides and Rp. capsulata). Note that chain twisting is not ascribed to the type of carotenoid, but rather to some specific interaction between the carotenoid and the protein environment and apparently affects the efficiency of singlet energy transfer. 

After an incubation period of 5 days, 97% of RDX was anaerobically degraded by a mixed population of purple photosynthetic bacteria of the genera Chromatium, Rhodospirillum, and Rhodopseudomonas, and possibly others (Navy 1973). Sixty percent of RDX was anaerobically degraded by Chromatium alone (Navy 1973). These photosynthetically active cultures, which do not release oxygen, were supplemented with sodium acetate and ammonium chloride. It was hypothesized that RDX was not actually metabolized, but rather was being reduced and modified as a result of the active electron transfer brought about by the anaerobic photosynthetic activity of the organisms. 

Aerobic bacteria such as Azotobacter vinelandii, Alcaligenes eutrophus, and Nocardia opaca, and facultative anaerobes, such as Escherichia coli and various species of Rhizobium and Bradyrhizobium (the symbionts of leguminous plants), also contain hydrogenase, as do photosynthetic bacteria such as Chromatium vinosum, Rhodobacter capsulatus (formerly Rhodopseudomonas capsulata), and Anabaena variabilis (a filamentous cyanobacterium). The thermophilic hydro-... 

Fry B, Gest H, Hayes JM (1984) Isotope effects associated with the anaerobic oxidation of sulfide by the purple photosynthetic bacterium, Chromatium vinosum. FEMS Microbiol Lett 22 283-287 Fry B, Gest H, Hayes JM (1985) Isotope effects associated with the anaerobic oxidation of sulfite and thiosulfate by the photosynthetic bacterium, Chromatium vinosum. FEMS Microbiol Lett 11 111-Til Fry B, Gest H, Hayes JM (1988a) " S/ S fractionation in sulfur cycles catalyzed by anaerobic bacteria. Appl Environ Microbiol 54 250-256... 

High potential iron-sulfur protein (HiPIP) is a special type of Fd which has been isolated from some photosynthetic bacteria and detected by ESR spectroscopy in other bacteria. HiPIP also contains a single 4Fe-4S cluster, but it differs from the other Fd in having a positive standard potential of about-h 350 mV (most Fd have standard potentials in the range of the hydrogen electrode, about -420 mV). Furthermore, the HiPIP from Chromatium is paramagnetic in the oxidized state. 

Photosynthetic bacteria and culture conditions. An axenic culture of the marine photosynthetic sulfur bacterium, Chromatium. sp. Miami PBS 1071 was cultured in a medium described previously (Ohta et al.. 1981) at approximately 30oC and 200 pE/m2/sec. Early stationary growth phase cultures were harvested (10,000 x g, 10 minutes), washed twice with 3% NaCl solution and then suspended in the same solution for hydrogen production. 

Ohta, Y., J. Frank and A. Mitsui. 1981. Hydrogen production by marine photosynthetic bacteria Effect of environmental factors and substrate specificity on the growth of hydrogen producing marine photosynthetic bacterium, Chromatium sp. Miami PBS 1071. Int. J. of Hydrogen Energy, 6, 451-460. 

Buchanan, Bachofen, and Arnon (29) found that extracts from Chromatium catalyzed a synthesis of pyruvate from acetyl-CoA, CO2, and reduced ferredoxin. Pyruvate did not accumulate in the absence of a trap, but was converted mainly to the amino acids, alanine, aspartate, and glutamate. Synthesis of these amino acids from acetate and CO2, by way of pyruvate, was in agreement with the earlier labeling data of Tomlinson (102) with anaerobic bacteria and of Cutinelli et al. (34) with another photosynthetic bacterium, Rhodospirillum rubrum. 

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