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A new type of short-wavelength delayed light emission from the photosynthetic bacteria Rhodospirillum rubrum and Rhodopseudomonas spheroides was found. The emission and action spectra suggest that magnesium protoporphyrin IX or a similar compound is the emitter. Anaerobic conditions were necessary to detect this long-lived emission. Some inhibitors of the primary processes of photosynthesis affected the intensity and the decay rate of the delayed light emission.

One of the obligate and basic requirements of Mitchell’s chemiosmotic hypothesis [ 1 ] is the consistency of the extent of the electrochemical potential difference of protons across the membrane and the amount of energy available for ATP synthesis. An estimation of this amount of energy has been obtained by measuring the maximal affinity of the phosphorylation reaction at which no net ATP synthesis occurs (phosphate potential in state 4). Experiments of this kind, performed in membrane systems as different as mitochondria [2], chloroplasts [3] and membrane fragments from aerobic [4] and photosynthetic bacteria [5], have all yielded values ranging between 14 and 16 Kcal/mole. These values are considered by several authors to be inconsistent with a stoichiometry of 2H’ translocated per ATP synthesized [ 1 ] and with the size of the proton electrochemical gradient, as estimated on the basis of the distribution of permeable ionic and protonable molecules across the energized membrane, for example [6,7]. Fluorimetric and spectrophotometric methods for the evaluation of pH or potential differences across the membranes of some photosynthetic bacteria have been propos d. Specifically, work in this laboratory [8] has indicated that ApH in bacterial chromatophores can be estimated from the extent of the fluorescence quenching of 9-aminoacridine, employing the technique originally proposed by Shuldiner et al. [9] for chloroplasts. In addition, the presence in photosynthetic membranes of pigments undergoing spectral shifts in response to a transmembrane electric field [lo] allows an evaluation of the membrane potential

A continuous culture apparatus is described, which allows cultivation of photosynthetic bacteria anaerobically in the light and semiaerobically in the dark at constant oxygen tensions. The growth-parameters 1. substrate concentration at half maximum growth rate (Ks) and 2. yield (Y) forRhodopseudomonas capsulata are calculated.

Chromatophores of Rhodospirillum rubrum catalyze a Pi-PPi exchange reaction in the dark. This reaction was inhibited by uncouplers of phosphorylation and ADP, and was stimulated by oligomycin. An energized state is therefore participating in this reaction. Methylene diphosphonate and fluoride which are inhibitors of the membrane-bound inorganic pyrophosphatase also inhibited and thus the reaction appears to be catalyzed by the pyrophosphatase. The Km for Pi was high (48 mm). For comparison, the PPi-Pi exchange reaction catalyzed by yeast inorganic pyrophosphatase was studied. Very high Pi and Mg2+ concentrations were required and, as expected, uncouplers had no effect on the reaction with the yeast enzyme. Under similar conditions the ratio of the exchange reaction to the hydrolytic reaction was considerably greater in chromatophores than with the yeast enzyme and this probably reflects the contribution of the energized state. The mechanism of the exchange in chromatophores is postulated to be due to the dynamic reversal of the energylinked hydrolytic reaction [see PDF for equation] where ∼x represents the energized state in general.

Purple nonsulfur bacteria, Rhodospirillum rubrum and Rhodopseudomonas spheroides were found to possess coenzyme B12-dependent glutamate mutase activity. Cell-free extracts of these bacteria grown on Co2+-containing media catalyzed the conversion of glutamate to β-methylaspartate and further to mesaconate. The activity of the cell-free extracts of these organisms cultivated on Co2+-deficient media was markedly lower than that of the normal cells. Addition of coenzyme B12 to the former reaction mixture enhanced the mesaconate formation via β-methylaspartate. These results indicate the involvement of coenzyme Independent glutamate mutase of these bacteria in the dissimilation of glutamate to acetyl-CoA and pyruvate through the following pathway.glutamate→β→methylaspartate→mesaconate→citramalate→→acetyl-CoA, pyruvate On the other hand, a greater part of glutamate was converted to α-hydroxyglutarate and succinate with the cell-free extracts of these photosynthetic bacteria. This fact, taking account of the pre...

Nutritional studies on four different strains of Chloroflexus, a new genus of filamentous, photosynthetic bacteria are described. This organism appears to be related to several different procaryotic groups, and in particular to the green sulfur bacteria and blue-green algae. Unlike these autotrophs, however, Chloroflexus is nutritionally diverse, being able to grow aerobically as a light-independent heterotroph, and anaerobically as a photoautotroph or photoheterotroph. Numerous organic carbon sources including hexoses, amino acids, short chain fatty acids, organic acids, and some alcohols are utilized under various growth conditions. These results suggest that this organism may be among the most nutritionally versatile organisms known.

Summary Similar linear dichroism (LD) spectra have been obtained for oriented samples prepared from photosynthetic bacteria containing either parallel lamellae (Rhodopseudomonas palustris) or spherical chromatophores (Rhodopseudomonas spheroides) in the spectral region from 300 to 1,000 nm. Our data indicate that the far-red QY transition moment of the bacteriochlorophyll (BChl) molecules is oriented nearly parallel to the plane of the membrane, and that the QX transition moment (590 nm) is tilted out of the membrane alone at an angle greater than 45°. The transition moment of the carotenoid molecules is shown to point out of the membrane plane. The LD spectrum of the R-26 mutant of R. spheroides allows the assign ment of the polarization direction of the main BChl transitions in the Soret region.

Experiments with resting cell suspensions of 15 species of hydrogenase-positive non-photosynthetic bacteria have shown that the organisms are able to depolarize the cathodic areas of a pure Fe surface by utilizing the polarizing hydrogen for the reduction of methylene blue. The results are completely consistent with the theory proposed by von Wolzogen Kuhr to explain the anaerobic corrosion of ferrous metals in neutral anaerobic environments. Two hydrogenase-negative organisms were shown to be unable to influence cathodic polarization.

— The behavior of glow curves and of ferricyanide-induced luminescence in photo-synthetic bacteria is consistent with a model in which light is emitted when electrons return to oxidized reaction center chlorophyll from the primary acceptor. A number of observations can be explained if it is assumed that the chromatophore membrane potential provides part of the activation energy for the process. The model is tested by inducing light emission by the generation of potassium diffusion potentials in preilluminated Chromatium chromatophores.

Nitrogen fixation has been shown to be a characteristic of two previously untested strains of the purple sulfur bacteriumChromatium sp.Chromatium strains have been shown to produce molecular hydrogen when suppliedD-L malate and bicarbonate in the presence of light and the absence of exogenous ammonia and molecular nitrogen. These results are discussed in relation to current findings on the nitrogen metabolism of the photosynthetic bacteria.

The photoreduction of cytochrome c by spinach chloroplasts has been noted by several investigators (12, 20, 25). In a preliminary report, we have presented evidence that aqueous digitonin extracts of spinach chloroplasts contain a cytochrome c photooxidase (22) which appears to be similar to the photooxidase present in extracts of photosynthetic bacteria studied by Kamen and Vernon (13, 14, 32). The present paper describes the behavior toward cytochrome c of whole chloroplasts prepared in hypertonic salt solution, and outlines the experiments which led to the demonstration of their cytochrome c-photooxidase activity.

The isolation and partial purification of mevalonic acid kinase from Euglena gracilis is described. The product of the reaction MVA-5-P has been characterized by paper chromatography. The apparent Km values for l-mevalonic acid, ATP, and Mg 2+ are 3 × 10 −5 m, 6 × 10 −3 m, and 9 × 10 −3 m, respectively. A concentration of 1 × 10 −3 m p -hydroxymercuribenzoate completely inactivates the enzyme. A distribution study has shown that mevalonic acid kinase is present in most higher plants and the algae Euglena gracilis and Chlamydomonas. No enzymatic activity could be detected in several species of photosynthetic bacteria or blue-green algae.

Four out of five soluble electron transport iron proteins of Thiocapsa pfennigii plus the particulate cytochromes have been found to be analogous to those of Chromatium vinosum strain D. In addition to ferredoxin, high potential iron-sulfur protein. cytochrome c′, and cytochrome c-552(550), T. pfennigii contains a cytochrome c-552(545) not previously isolated from photosynthetic bacteria. It is concluded that T. pfennigii is more closely related to C. vinosum than to Rhodopseudomonas viridis, the only other known bacterial species having bacteriochlorophyll b.

Ever since men noticed yellowing autumnal leaves, or gathered brown, red, or blue algae, they must have speculated as to the meaning of these colors. Scientific interest became the more acute as physiologists realized the universal distribution of chlorophyll in photosynthetic systems, and its undoubted importance as the primary light absorber. But the other pigments are also widespread: one (f3-carotene) is almost always present, and there are usually several others found in every photosynthetic system. Their distribu­ tion is remarkably parallel to phylogenetic lines. What are these other pigments doing? Are they accidental and indifferent, merely happening to absorb light (like hemoglobin) without this absorption having much physiological function? Are they helpful or wasteful filters, by their absorption protecting other systems from injurious or useful radiation? Are they, perhaps, themselves injurious, inducing photodynamic or photo­ oxidative effects? Do they collaborate with chlorophyll, optically or chemical­ ly, thereby qualifying as truly "accessory"? Or are they completely inde­ pendent, supplementary light absorbers, with their own parallel complement of enzyme systems, able to carry out photosynthesis without the interven­ tion of chlorophyll? Indeed, do they sometimes take over the major absorb­ ing function, subordinating chlorophyll itself to an accessory or indifferent position? This chapter attempts to summarize current information on the role of the so-called "accessory pigments" in photosynthesis. There has been brief mention of these in various recent reviews (1 to 5), and Rabinowitch has given his usual excellent discussion of the problem [(6), chaps. IS, 17; (7), chaps. 21-24, 30]. Several comprehensive descriptions of the pigments, with­ out much emphasis on their function, have appeared lBoresch (8); Cook (9); Strain, (10, 11, 12)]. The present author has assembled some of the back­ ground, as well as new material, especially on the algae, in a forthcoming chapter [Blinks (13)]. No attempt is made here to include photosynthetic bacteria, which will be covered in Volume 8 of the Annual Review of Micro­ biology.

The amino acid composition of the hydrolysate of photosynthetic bacteria, Rhodo-pseudomonas capsulatus, was analyzed automatically by using the amino acid analyzer and it was found that in the bacteria, histidine, proline, alanine, valine, methionine, tyrosine and tryptophan were present in larger amounts than in Chlorella vulgaris and yeast, Saccharomyces anomalus. Especially, the content of methionine was much higher; 5 times more than chlorella and 3 times more than yeast. This work was supported by the grants from the Ministry of Education.

Summary. Thin sections of methane-utilizing bacteria have been examined in the electron microscope and the fine structure of the cells is described for the first time. The outstanding feature of all the isolates studied is the existence of intracellular membrane structures resembling those seen in nitrifying and photosynthetic bacteria. The possible significance of these membranes is discussed.

A new apparatus is described which permits pure cultivation of 110 l amounts of phototrophic organisms. Some data are given to prove its utility for mass production (kilogram amounts) of algae and photosynthetic bacteria.

A B S T R A C T Chlorella pyrenoidosa (van Niel's strain) was cuLltured in four environmental conditions: lightglucose, light-galactose, dark-glucose, and dark-galactose. The gradtual change in structture was observed when the cultures were transferred from light to darkness (dark adaptation). Cells grown in light contained well-developed chloroplasts and the normal cytoplasmic sub-units. During the transition to the complete heterotrophic mode of nutrition, the chloroplast regressed to the proplastid stage with a gradual reduction in thylakoid number. A prolamellar body was noted in the most regressed proplastid condition and plastid storage material was observed in all stages. The cell wall thickened during the transition. Cells adapted to darkness on galactose exhibited abundant cytoplasmic storage material with osmiophilic properties. SOME MICROORGANISMS do not grow in continuous darkness. Wetherell (1958) reported that certain blue-green algae, diatoms, green algae, and photosynthetic bacteria failed to grow in dark

— The use of sodium dodecyl sulfate to dissociate photosynthetic membranes followed by standard fractionation techniques yields chlorophyll-proteins and reaction center complexes with molecular weights of 500,000 or less. Much about the structure and function of photo-synthetic units in vivo can be deduced from the properties of the isolated complexes. The Bchl-protein from green bacteria is approximated by an incompletely filled sphere ˜ 80 Â in diameter consisting of four identical subunits. The five Bchl molecules in each subunit are 14 to 20Â apart. The related Chl a-proteins from a blue-green alga and various eukaryotic plants may have similar structural characteristics. The Chl a-protein from a blue-green alga contains one molecule of P700 per 60–90 Chl a molecules. The quantum requirement for P700 oxidation is 2.6 or less. The midpoint potential in various preparations ranges from 0.38 V to 0.42 V. Green algae and higher plants yield a Chl a-protein similar to that from the blue-green alga; in addition they yield another Chl-protein (mol. wt. = 2–3×104) which contains an equal amount of Chl a and Chl b. These two Chl-proteins account for most of the chlorophyll in these organisms. Two photosynthetic bacteria (Rhodopseudomonas viridis and Chromatium) yield protein complexes containing Bchl, carotenoid, and bound cytochromes. The reaction center complex from R. viridis contains P960 (Em, 8= 0.39 to 0.42 V), cytochrome 558 (Em,8= 0.33 V) and cytochrome 553 (Em,7=— 0.02 V). Quantum requirements for P960 and C558 oxidation are ˜2.2 and 3.0, respectively. Complex A from Chromatium contains Bchl 890, P883, cytochrome 556 (Em,8= 0.34 V) and cytochrome 552 (Em,7=˜0.04 V). The quantum requirement for C556 oxidation is about 15. Both high- and low-potential cytochromes can donate electrons to the reaction center chlorophyll present in either complex. This fact supports the idea that only one kind of photochemical reaction center functions in photosynthetic bacteria. An hypothesis about the nature of the photosynthetic unit in purple bacteria is outlined.

1. The relative intensity of delayed singlet emission from chlorophyll was measured from 10 −3 sec to 10 2 sec after cessation of illumination in the wild-type and two non-photosynthetic mutants of a green alga, Scenedesmus obliquus . 2. Mutant 11, in which the oxygen-evolving, short-wavelength photoreaction (photoreaction II) was blocked, emitted very low intensities of delayed light compared with the wild-type. When the emission was averaged from 0.75 to 4.2 msec from the center of a flash of exciting light, the wild-type emitted 250 times the intensity emitted by mutant 11. 3. Mutant 8, in which the pyridine nucleotide-reducing, long-wavelength photoreaction (photoreaction I) was blocked, emitted delayed light with different decay kinetics from those of the wild-type. In the millisecond time range, mutant 8 emitted higher intensities of delayed light, and the emission decayed very slowly. In the second time range, mutant 8 emitted lower intensities than the wild-type, and the decay was rapid. 4. On the basis of the two-photoreaction hypothesis, and of the earlier evidence from photosynthetic bacteria which indicates that functional reaction centers are required in order for delayed light to be emitted, the weak emission from mutant 11 implies that nearly all delayed light from normal plants is due to energy storage by photoreaction II. 5. The altered decay kinetics of mutant 8 (higher intensity, slower decay) in the msec time range are shown to be consistent with the Hill and Bendall hypothesis of two photoreactions linked by an electron-transport chain. Lack of function of photoreaction I would result in a completely reduced electron-transport chain which could not accept reducing equivalents from photoreaction II. 6. The altered decay kinetics of mutant 8 in the second time range are shown to be inconsistent with any modification of the Hill and Bendall hypothesis which does not provide a pathway for reducing equivalents to migrate from photoreaction I to photoreaction II. A comparison of this long-term delayed light in the wild-type and mutant 8 implies the presence of a slow charge migration (1–50 sec) in the wild-type from photoreaction I to photoreaction II, which in turn results in long-term light emission by photoreaction II. 7. Two modifications of the Hill and Bendall hypothesis, both of which provide for appropriate charge migration, are discussed. The present data may be accounted for either by the addition of a second electron-transport chain or by a single inhomogeneous pigment system which harvests energy from two spatially separated reaction centers. The latter hypothesis also accounts for a number of previously published observations.

A comparison has been made between Signal I, the photo-electron spin resonance signal associated with the primary light conversion act in photosynthesis, and free-radical signals generated in various chlorophyll species in vitro . The esr signals obtained from chlorophyll·monomer, (Chl·L) +. , chlorophyll dimer, (Chl 2 ) +. , and chlorophyll oligomer, (Chl 2 ) n +. , are broader than Signal I, whereas the chlorophyll-water adduct, (Chl·H 2 O) n +. , gives a signal very much narrower than Signal I. The unusually narrow signal from (Chl·H 2 O) n +. has been ascribed to spin migration, or to unpaired spin delocalization over a large number of chlorophyll molecules. The linewidth of Signal I can be accounted for by a similar delocalization process. A theoretical relationship between the esr linewidth and the number of chlorophyll molecules, N, over which an unpaired spin is delocalized, takes the form ΔH N = 1/√N·ΔH M , where ΔH M is the linewidth of monomer (Chl·L) +. . This relationship for N = 2 accounts well for the linewidths of Signal I in green algae, blue-green algae, and photosynthetic bacteria in both the 1 H- and 2 H-forms. The linewidth of Signal I (as well as the optical properties of reaction-center chlorophyll) are consistent with unpaired spin delocalization over an entity containing two chlorophyll molecules, (Chl·H 2 O·Chl) +. .

In the preceeding paper (1), it was reported that when R. capsulatus is mixed with B. subtilis, in spite of no nitrogen fixation in separate cultures, by using a glycerol or starch medium, the combination was able to fix molecular nitrogen and it seems that there is a correlation between the production of pyruvic acid and the nitrogen fixation in the mixed culture.

Tests (by enrichment culture) for nonsulfur purple photosynthetic bacteria in surface soils showed them in all of three sediment cores sampled in a shallow pond and in all of six peats from nearby swamp hollows beneath cedar and tamarack. They also occurred in two of three peats from swamp flats and three of five peats from swamp hummocks. For woodland and grassland surface soils, proportions were three out of seven and five out of nine sites respectively. For the total number of tubes inoculated at varying dilutions from each of these sites, the following proportions of positives were recorded: uppermost lake sediments 92%, swamp hollows 67%, swamp flats 38%, swamp hummocks 20%, woodlands 14%, grasslands 8%.

1. The substrate-dependent oxygen uptake of Chromatium D has been measured. Although the rates observed were only of the order of 1 μmole/hour x mg dry weight, they are comparable with the rates found for other photosynthetic bacteria. 2. Light inhibits the rate of O2 consumption of suspensions equilibrated with excess substrate, but may stimulate the rates in previously starved suspensions. 3. Prolonged aeration of suspensions of Chromatium with thiosulfate leads to accumulation of sulfur globules in the cells, and does not lead to a rapid loss of viability. 4. Measurements of ATP content of suspensions after exposure to air indicate a limited capacity for oxidative phosphorylation in Chromatium.

In this paper the purification of some industrial waste water by photosynthetic microbes is discussed. The method used did not produce sludge and this has considerable advantages over other existing techniques. The by-products of the treatment (photosynthetic bacteria and green algae) were used as food for animals and fish, and as a fertilizer. It was found that the photosynthetic bacterial cells served not only as a source of food but also they increased survival in fish, increased egg production in hens and improved the quality and quantity of citrus fruit when applied as an organic fertilizer.

— Cells and chromatophores of the photosynthetic bacterium Rhodopseudomonas viridis were frozen in the dark and illuminated while frozen or were illuminated during freezing. Upon being heated they emitted light. The conditions under which glow curves could be produced and the kinetics of the light emission indicate that the glows resulted from the thermal release of electrons from secondary electron acceptors and their recombination with oxidized reaction center bacteriochlorophyll b. Glow curves could not be obtained with Rhodospirillum rubrum.

In the photosynthetic bacteria Chromatium, Rhodopseudomonas spheroides and Rhodospirillum rubrum light-induced cytochrome oxidation was studied at temperatures between 20 and -220°. Of all cytochromes studied, only one, C 423.5 in Chromatium , was photooxidized at -220°. The photooxidation of C 420 in R. rubrum stops at about -30° and that of C 422 in Chromatium between −75 and -120°. The photooxidation of other cytochromes studied stops at temperatures between −30 and -120°. By recording, as a function of the wavelength, the difference in absorbancy of two cuvettes with bacteria, of which one could be illuminated, it was shown that, contrary to earlier suggestions, the cytochromes remain in the reduced state during cooling in the dark. The quantum requirement for C 423.5 and C 422 oxidation in Chromatium was calculated to be about 0.75 and 0.65, respectively, assuming a specific extinction change of 62 mM −1 cm −1 for both C 423.5 and C 422 at 422 mμ, which suggests that the quantum requirement is close to 1 and that the true specific extinction is somewhat higher. The rate of initial photooxidation as a function of intensity was found to be saturated at decreasing intensities, for the cytochromes studied, if the temperature was lowered sufficiently. This suggests that cytochrome photooxidation is not a primary, but a “dark” reaction. The light-induced increase in absorbancy around 435 mμ in R. rubrum , which also occurs at lower temperatures, had kinetics and saturating curves different from those occuring in the infrared, which showed that these absorbancy changes were caused by different reactions.

α-Ketoglutarate synthase from the photosynthetic bacterium Chlorobium thiosulfatophilum, an enzyme that catalyzes the formation of α-ketoglutarate by a reductive carboxylation of succinyl-CoA, was purified about 120-fold by high speed centrifugation, fractionation with protamine sulfate, column chromatography on DEAE-Sephadex, and sedimentation in a sucrose gradient. α-Ketoglutarate synthase is readily inactivated by oxygen; strictly anaerobic conditions are essential for preserving enzyme activity during purification, handling, and storage. The reductive synthesis of α-ketoglutarate from succinyl-CoA and bicarbonate requires reduced ferredoxin. Of several ferredoxins tested, only those from the photosynthetic bacteria C. thiosulfatophilum, Chromatium, and Rhodospirillum rubrum were effective. The ferredoxins of Clostridium pasteurianum and spinach were found to be poor substitutes for those of photosynthetic bacteria. The reversibility of the α-ketoglutarate synthase reaction was demonstrated by the use of α-ketoglutarate, CoA, and one of several electron acceptors in substrate amounts: FAD, FMN, triphenyltetrazolium chloride, or ferredoxin. NAD and NADP were ineffective. Purified preparations of α-ketoglutarate synthase show, in the presence of either CoA or reduced ferredoxin, an active 14C exchange between [14C]bicarbonate and α-ketoglutarate. α-Ketoglutarate synthase was found to be distinct from pyruvate synthase with respect to molecular size and chromatographic properties. The molecular weights and sedimentation coefficients of α-ketoglutarate synthase and pyruvate synthase were found to be, respectively, 220,000 and 9.0 S and 300,000 and 10.7 S.

Detailed studies of the properties of carotenoids isolated from diphenylamine-inhibited cultures of Rhodospirillum rubrum have revealed a number of novel structures that indicate new features of carotenoid biosynthesis in the photosynthetic bacteria. Both neurosporene and 7,8,11,12-tetrahydrolycopene undergo hydration, methylation and dehydrogenation to yield spheroidene and 11′,12′-dihydrospheroidene respectively; all the intermediates in these pathways have been identified. These pathways represent alternative routes of anhydrorhodovibrin and spirilloxanthin biosynthesis.

The alga Chlamydomonas mundana Gerloff appears in great numbers in waste stabilization lagoons of the Mojave Desert during periods of anaerobic operation. The alga perpetuates anaerobiosis, since its feeble photosynthetic oxygen production is not sufficient to compensate for its own oxygen consumption in the presence of acetate. Growth of Chlamydomonas mundana is encouraged by anaerobic conditions that favor acetate production by anaerobic bacteria. Most of the acetate used by the alga is directly assimilated by a photosynthetic mechanism involving photosynthetic production of ATP and reducing power. This process resembles that of photosynthetic bacteria more closely than that of common sewage algae, such as Chlorella and Scenedesmus, which rapidly assimilate carbon dioxide and release oxygen. The possibility that the photometabolism of organic substrates by phytoplankton may be more widespread than the limited environment represented by an anaerobic lagoon is discussed.

A comparison of the biosynthesis of unsaturated fatty acids in higher plants, Chlorella vulgaris and photosynthetic bacteria showed that only the first two systems require oxygen as a cofactor. Photosynthetic bacteria degrade added fatty acids to acetate and synthesize their unsaturated acids by the anaerobic route irrespective of the presence or absence of air. Leaves and Chlorella synthesize linoleic and linolenic acids from oleic acid by direct desaturation. Oleic acid is synthesized differently by the two systems. Leaves degrade added fatty acids by α-oxidation photosynthetic bacteria by β-oxidation.

Measurements have been made of changes in absorption spectra of anaerobic suspensions of several kinds of photosynthetic bacteria following illumination or aeration in the dark. The difference spectra obtained show that oxygenation or illumination results in a decrease in the absorption bands corresponding to the carotenoid pigments of the bacteria, and new absorption bands appear at longer wavelengths. It is also apparent that cytochrome pigments are oxidized on addition of oxygen or on illumination. However, some cytochrome pigments appear to be specifically involved in light-induced reactions.