Preparation and properties of bacterial chromatophores entrapped in polyacrylamide

The immobilization of Rhodospirillum rubrum chromatophores was successfully performed by entrapping them in polyacrylamide. Their photophosphorylating activity was about 40% of native chromatophores. The temperature and pH optima for immobilized chromatophores were similar to the native photosynthetic apparatus and kinetic parameters showed that the rate of photophosphorylation in polyacrylamide particles was diffusion controlled. Light penetration of the gel particles was not a limiting parameter. Immobilization considerably increased the stability of the chromatophores towards denaturation.     

Die Zweiteiligkeit der Chromatophoren bei Cryptomonaden

In theChrysophyceae as well as in different species ofCryptomonas bilobed chromatophores are present. These chromatophores consist of two large parietal lobes closed to the lateral sides of the cell and joined by a narrow bridge on its dorsal part. A survey of all species with a single bilobed chromatophore is given. Besides, also species with two separate chromatophores have been found. The presence of several chromatophores inCryptomonas cells is doubtful. The morphology of the chromatophores has to be taken into consideration in the taxonomy ofCryptomonas.

     

The fine structure of odonata chromatophores

The appearance, fine structure and pigment composition of the epidermal chromatophores of mature Austrolestes annulosus (Lestidae) are described and compared with the developing chromatophores of teneral Austrolestes and the mature chromatophores of Diphlebia lestoides (Amphipterygidae) and Ischnura heterosticta (Caenagrionidae). Mature chromatophores contain masses of near spherical light-scattering bodies and larger irregularly shaped pigment vesicles. These effect colour change by migrating in opposite directions, through a system of interconnecting granular endoplasmic reticulum tubules. The pigment, a mixture of xanthommatin and dihydroxanthommatin, has a liquid or gelatinous consistency. Developing chromatophores of teneral insects lack light-scattering bodies and well-defined migratory pigment vesicles, but contain irregular masses of pigment of similar chemical composition.     

Elektronenmikroskopische Untersuchungen über die Entwicklung der „Chromatophoren” von Rhodospirillum molischianum Giesberger

Summary The chromatophores of Rhodospirillum molischianum originate de novo from the cytoplasmic membrane. Their laminar membranes arise by invagination of the cytoplasmic membrane and these have a circular shape. 5–15 of these membranes are piled up to form the chromatophores. Probably, the membranes of the chromatophores remain always connected with the cytoplasmic membrane by a tubular stalk.     

Improvement of photosynthesis in zooxanthellate corals by autofluorescent chromatophores

Autofluorescent chromatophores were detected in 17 out of 71 zooxanthellate coral species studied. Chromatophores are localized either in the oral gastrodermic (endoderm) or oral epidermis (ectoderm). The pigment granules within the chromatophores (0.5–1.0 m in diameter) show a brilliant light-blue/turquoise autofluorescence (emission between 430 and 500 nm) after excitation with light of 365–410 nm. All species where the autofluorescent gastrodermal chromatophores form a compact layer, embedding the zooxanthellae, belong to the family Agariciidae. In contrast, some species of the Faviidae (2), Pectiniidae (1) and Mussidae (1) were found to have distinct, autofluorescent chromatophores in the oral epidermis. Autofluorescent pigments of the host may enhance photosynthesis of the symbionts as in Leptoseris fragilis. Short wavelength irradiance, less suitable for photosynthesis, is transformed by host pigments into longer wavelengths which are photosynthetically more effective. Thus, host species possessing autofluorescent chromatophores might have selective advantage over non-fluorescent species, and have the potential to survive in light-limited habitats. Furthermore, the daily period of photosynthesis is extended, thus increasing the energy supply and enhancing the deposition of skeletal carbonate. The absence or presence of chromatophores may have value in taxonomy and could putatively be of plalaeontological and palaeoecological interest.     

Rotational mobility of the photoreaction center in chromatophore membranes of Rhodospirillum rubrum

We investigated the rotational mobility of the photoreaction center in chromatophores of Rhodospirillum rubrum by studying the photoinduced linear dichroism of absorption changes at 865 nm. The study was carried out in suspensions of chromatophores treated with ferricyanide in order to bleach their antenna bacteriochlorophyll and thus minimize depolarization by energy transfer. Very little depolarization of the photoinduced absorbance change at 865 nm was observed at room temperature for chromatophores immersed in a highly viscous medium over the time range 0–10 ms following an exciting light flash. In the light of independent evidence for transmembrane arrangement of the photoreaction center, we conclude that the photoreaction center protein is immobilized in the chromatophore membrane for at least 10 ms.     

Lipid-protein associations in chromatophores from the photosynthetic bacterium Rhodopseudomonas sphaeroides.

Lipid-protein interactions were examined in chromatophores isolated from the photosynthetic bacterium Rhodopseudomonas sphaeroides using lipid spin-labels. The chromatophores contain fluid bilayer and a significant amount of lipid immobilized by membrane proteins. For a typical preparation of cells grown under 600 ft-c illumination, 59% of the spin-labeled fatty acids were bound. Essentially the entire length of the 18-carbon fatty acid chain was immobilized, judging from results obtained with the spin-label at the 7, 12, and 16 positions. The amount immobilized varies directly with the bacteriochlorophyll content of the chromatophore material, suggesting that a significant fraction of the lipid spin-labels is immoblized on the hydrophobic surfaces of the chlorophyll-binding proteins. Changing the lipid spin-label head group from a negatively charged carboxyl group to a positively charged quarternary amine greatly decreased the amount of immobilized lipid. The changes in immobilized lipid with light level and polar head group suggest that the anntenna bacteriochlorophyll-binding proteins preferentially associate with negatively charged lipids.     

Morphological and Biochemical Characterization of the Cream Markings in the Integument of the Female Isopod,Armadillidium vulgare

Cream markings aligned along the dorsal region of the female isopod, A. vulgare, were investigated with light and a fluorescence microscope and an electron microscope. Biochemical studies were also carried out. The cream markings were observed in the dorsal integument as a group of cream-colored chromatophores that emit a yellow fluorescence. These chromatophores, which are distinguishable from ommochrome chromatophores, contained numerous granules in the cytoplasm, and these granules (0.6–3.0 μm in length by 0.4–1.5 μm in width) were electron-lucent and spheroidal in shape with a concentric arrangement of membranes. Based on various biochemical analyses, the principal component of the yellow pigment isolated from the cream markings was identified as sepiapterin. These facts revealed that the cream markings are the chromatophores that contain pteridine granules. The males have no cream markings like those of the females, since the cream-colored chromatophores are externally hidden by the ommochrome chromatophore layer. The content of sepiapterin in the males was about two times greater than that in the females. This quantitative difference in sepiapterin content between males and females suggests that the pteridine formation in this pigment cell may be regulated by hormones associated with sex determination.     

Structural and functional properties of chromatophores and membrane vesicles from Rhodepseudomonas sphaeroides

Membrane vesicles have been isolated by a modified procedure from Rhodopseudomonas sphaeroides, grown phototrophically under high light intensity. In addition,chromatophores have been isolated from this organism grown phototrophically with low light intensities.Structural, chemical and functional properties of both preparations have been investigated and compared. The orientation of the membrane preparations has been studied by freeze-etch electron microscopy, the localization of cytochrome c₂, and light-driven active transport of amino acids and Ca²⁺. The results demonstrate that the orientation of the vesicle membrane is the same as the cytoplasmic membrane of intact cells; the membranes in chromatophores, however, have an inverted orientation.On a dry weight basis, the membrane vesicles contain less protein, carotenoids and bacteriochlorophyll and more lipids than do chromatophores. Qualitatively, however, the composition of both preparations is similar.It is concluded that the intracytoplasmic structures from which the chromatophores are derived are structurally and functionally similar to (and most likely continuous with) the cytoplasmic membranes from which the vesicles are derived.     

The mobility of chromatophore membranes from Ectothiorhodospira Shaposhnikovii revealed by Rayleigh scattering of Mössbauer radiation (RSMR) experiments

Chromatophores from Ectothiorhodospira Shaposhnikovii in solvents of different viscosity were investigated by RSMR experiments in the temperature range between 112 K and room temperature. Additional RSMR-experiments were done on solvents only. The mobility of the molecules and within the molecules is the given by the Debye-Waller factor which yields the meansquare displacement, , averaged over the atoms in the system. The mobility of the atoms of the chromatophores roughly follows the mobility of the atoms of the solvents. At low temperatures the mobility of the chromatophores remains slightly larger than the mobility of the frozen solvent. At room temperature, however, of the chromatophores remains significantly smaller.Chromatophores in a glycerol-water mixture (0.001 M Tris-HCl buffer) and in water (0.05 M Tris-HCl buffer) show a different dynamic behaviour. A region with enhanced mobility near T=180 K was indicated for the chromatophores in the glycerolwater mixture.A correlation has been suggested between the rate of electron transfer from the primary to the secondary quinone and the increase of the conformational mobility of the chromatophores in glycerol-water mixture.Abbreviations Mb Myoglobin - Met-Mb Metmyoglobin     

Untersuchungen zur Substruktur der “Chromatophoren” von Rhodospirillum rubrum und Rhodospirillum molischianum

Summary Electron microscopy of ultrathin sections reveals that in the photosynthetic bacterium Rhodospirillum molischianum Giesberger numerous discrete discs, the chromatophores, are developed. The chromatophores are 300 m in diameter and have a thickness of 70 to 80 m. In their substructure they show piled-up plates, the lamellae. The dense plates are about 45 Å thick with less dense interspaces of 50 Å. The small vesicular chromatophores of Rhodospirillum rubrum Esmarch are surrounded by membranes and have a diameter of about 70 m. The chromatophores of both species are arranged at the periphery of the cell. A definition of the two strains on the fundamentals of morphological features is given. The absorption-spectra of the pigment extracts exhibit characteristic differences.     

The Dibromothymoquinone Effect on Membrane Potential Generation in Rhodospirillum rubrum Chromatophores

2,5-Dibromo-3-methyl-6-isopropyl benzoqui-none (DBMIB) inhibits the light-dependent membrane potential generation in Rhodospirillum rubrum chromatophores. The inhibition is relieved by electron donors and is obviously due to oxidation of the photosynthetic electron transfer chain components. In addition, high DBMIB concentrations elicit another effect probably caused by disruption of quinone functions in chromatophores. However, in quinone-depleted chromatophores and proteoliposomes containing the P-870 reaction center and light-harvesting antenna complexes, DBMIB stimulates membrane potential generation in the light, probably restoring some of the quinone-dependent processes in the membrane. DBMIB inhibits the inorganic pyrophosphate- and ATP-in-duced membrane potential generation in chromatophores.     

Zur Morphologie und Entwicklungsgeschichte vonEunotia-Arten (Bacillariophyceae)

After allogamous pairingEunotia tenella produces in each partner cell one gamete containing the two chromatophores of the mother cell and one abortive protoplast without chromatophores. This distribution results from a differential cytokinesis which exhibits the same constant orientation in regard to the epi- resp. hypotheka as in other species ofEunotia. Moreover inEu. tenella andEu. spec. the significant right hand—left hand dissymmetry during the growth of the daughter chromatophores in vegetative cytokinesis is the same as in other species. Both phenomena are significant for the genus and unique. In connection with the diminution of cell size in vegetative divisions the bending of the valvae increases to a certain degree.

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Zur Morphologie und Entwicklungsgeschichte vonEunotia-Arten (Bacillariophyceae)

     

Bacteriochlorophyllgehalt und Proteinmuster der Thylakoide von Rhodospirillum rubrum während der Morphogenese des Photosynthese-Apparates

Zusammenfassung Der Zusammenhang zwischen dem spezifischen Bacteriochlorophyllgehalt der Zellen und der Thylakoidmorphogenese wird an Rhodospirillum rubrum untersucht. Bei der Induktion des Photosynthese-Apparates wird zunächst Bacteriochlorophyll synthetisiert, obgleich noch keine Thylakoide gebildet werden (1. Phase). Werden Thylakoide ausgebildet, so steigt der spezifische Bacteriochlorophyllgehalt der Thylakoide in Abhängigkeit vom spezifischen Bacteriochlorophyllgehalt der Zellen an, bis ein Wert von 12–13 g Bacteriochlorophyll je mg Zellprotein erreicht ist (2. Phase). Während der Wert für die Zellen darüber hinaus weiter erhöht werden kann, bleibt der Wert der Thylakoide konstant bei 100 g Bacteriochlorophyll je mg Thylakoid-Protein (3. Phase). Isolierte Thylakoide aus Zellen mit niedrigem Bacteriochlorophyllgehalt besitzen geringere Durchmesser als Thylakoide aus Zellen mit höheren Werten. Auch hinsichtlich der Zusammensetzung der Thylakoide in Abhängigkeit von den steigenden Bacteriochlorophyllgehalten bei induzierten Zellen konnten Unterschiede festgestellt werden. Ähnlich wie die spezifischen Bacteriochlorophyllgehalte der Thylakoide, nähern sich die verschiedenen Proteinbausteine der Thylakoide einem festen Verhältnis zueinander, das sich oberhalb von 10–14 g Bacteriochlorophyll je mg Zellprotein nicht mehr ändert. Mit Zunahme des Bacteriochlorophyllgehaltes der Zellen steigt der Gehalt an thylakoidspezifischen Proteinen in den Membranen an und der Anteil der für die Cytoplasmamembran spezifischen Komponenten nimmt ab.

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The bacteriochlorophyll content and protein composition of chromatophores (=thylakoids) of Rhodospirillum rubrum during morphogenesis of the photosynthetic apparatus

Summary The correlation between the specific bacteriochlorophyll content of whole cells and the morphogenesis of chromatophores was investigated in Rhodospirillum rubrum. During the first phase after induction of the photosynthetic apparatus bacteriochlorophyll is synthesized without formation of chromatophores. In a second phase chromatophores increases in a linear correlation to the specific bacterichlorophyll content of the cells. In a third phase, when the specific bacteriochlorophyll content of the cells has reached 12–13 g/mg protein, the specific bacteriochlorophyll content of the chromatophores remains constant (100 g/mg protein). Isolated chromatophores from the second phase have smaller diameters, than chromatophores from the third phase. The composition of the protein compounds of isolated chromatophores changes during the development of the chromatophores in a similar fashion as the specific bacteriochlorophyll content of chromatophores does change. With increasing bacteriochlorophyll content of the cells the chromatophore specific proteins in the membranes increase whereas proteins specific for the cytoplasmic membrane decrease until both reach a constant level.

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Verwendete Abkürzungen BChl. Bacteriochlorophyll     

Observations on the ultrastructure and distribution of chromatophores in the skin of chelonians

Alibardi, L. 2011. Observations on the ultrastructure and distribution of chromatophores in the skin of chelonians. —Acta Zoologica (Stockholm) 00 :1–11. The cytology and distribution of chromatophores responsible for skin pigmentation in chelonians is analyzed. Epidermal melanocytes are involved in the formation of dark spots or stripes in growing shelled and non‐shelled skin. Melanocytes rest in the basal layer of the epidermis and transfer melanosomes into keratinocytes during epidermal growth. Dermal melanophores and other chromatophores instead remain in the dermis and form the gray background of the skin. When dermal melanophores condense, they give origin to the dense spots or stripes in areas where no epidermal melanocytes are present. In the latter case, the epidermis and the corneous layer are transparent and reveal the dermal distribution of melanophores and other chromatophores underneath. As a result of this basic process of distribution of pigment cells, the dark areas visible in scales can have a double origin (epidermal and dermal) or a single origin (epidermal or dermal). Xanthophores, lipophores, and a cell containing both pterinosomes and lipid droplets are sparse in the loose dermis while iridophores are rarely seen in the skin of chelonians analyzed in the present study. Xanthophores and lipophores contribute to form the pale, yellow or oranges hues present among the dark areas of the skin in turtles.     

Fish chromatophores as cytosensors in a microscale device: detection of environmental toxins and bacterial pathogens

Fish chromatophores from Betta splendens are used as the cytosensor element in the development of a portable microscale device capable of detecting certain environmental toxins and bacterial pathogens by monitoring changes in pigment granule distribution. The adaptation of chromatophores to a microscale environment has required the development of enabling technologies to produce miniaturized culture chambers, to integrate microfluidics for sample delivery, to miniaturize image capture, and to design new statistical methods for image analyses. Betta splendens chromatophores were selected as the cytosensor element because of their moderate size, their toleration of close contact, and most importantly, for their responses to a broad range of chemicals and pathogenic bacteria. A miniaturized culture chamber has been designed that supports chromatophore viability for as long as 3 months, and that can be easily transported without damage to the cells. New statistical methods for image analyses have been developed that increase sensitivity and also decrease the time required for detection of significant changes in pigment granule distribution. Betta chromatophores have been tested for their responses to selected pathogenic bacteria and chemical agents. We discuss in detail the aggregation of pigment granules seen when chromatophores are incubated with Bacillus cereus, a common cause of food poisoning. Also described are the more subtle responses of chromatophores to a class of environmental chemical toxins, polynuclear aromatic hydrocarbons. We show that the chromatophores are able to detect the presence of certain polynuclear aromatic hydrocarbons at concentrations lower than the Environment Protection Agency (EPA) 550.1 standards.     

Influence of light on long-term ADP phosphorylation

ADP phosphorylation coupled to cyclic electron transport was studied over a long period using immobilized chromatophores from Rhodopseudomonas capsulata. Photophosphorylation of ADP as a function of time was continuously measured under different conditions of continuous illumination and concentration of oxygen. Using a red cutoff filter, it was possible to sustain ADP phosphorylation at a maximal rate for more than 10 days, whereas inactivation had always been observed after 5 days when white light was used. The influence of light nature on inactivation was demonstrated using photopigment absorption spectra.     

A new sexually dichromatic miniature Hyphessobrycon (Teleostei: Characiformes: Characidae) from the Rio Formiga,upper Rio Juruena basin,Mato Grosso,Brazil, with a review of sexual dichromatism in Characiformes

Hyphessobrycon myrmex sp. nov., is described from the Rio Formiga, upper Rio Juruena, upper Rio Tapajós basin, Mato Grosso, Brazil. The new species can be distinguished from congeners by having the lower half of the body deeply pigmented with dark chromatophores, chromatophores concentrated above the anal fin and forming a broad, diffuse, dark midlateral stripe and by having a dense concentration of dark chromatophores along unbranched dorsal‐fin rays and distal portions of the two or three subsequent branched rays. In life, H. myrmex exhibits a conspicuous sexual dichromatism, with adult males red to orange and females and immatures pale yellow. A list containing 108 sexually dichromatic taxa in six families of Characiformes is provided and the distribution of this poorly known type of dimorphism across the Characiformes is discussed.     

Examination of the putative Ca<Superscript>2+</Superscript>-binding site in the light-harvesting complex 1 of thermophilic purple sulfur bacterium <Emphasis Type="Italic">Thermochromatium</Emphasis><Emphasis Type="Italic">tepidum</Emphasis>

The core light-harvesting complex (LH1) of purple sulfur photosynthetic bacterium Thermochromatium tepidum exhibits an unusual absorption maximum at 915 nm for the Q _y transition, and is highly stable when copurified with reaction center (RC) in a LH1–RC complex form. In previous studies, we demonstrated that the calcium ions are involved in both the large red shift and the enhanced thermal stability, and possible Ca²⁺-binding sites were proposed. In this study, we further examine the putative binding sites in the LH1 polypeptides using purified chromatophores. Incubation of the chromatophores in the presence of EDTA revealed no substantial change in the absorption maximum of LH1 Q _y transition, whereas further addition of detergents to the chromatophores-EDTA solution resulted in a blue-shift for the LH1 Q _y peak with the final position at 892 nm. The change of the LH1 Q _y peak to shorter wavelengths was relatively slow compared to that of the purified LH1–RC complex. The blue-shifted LH1 Q _y transition in chromatophores can be restored to its original position by addition of Ca²⁺ ions. The results suggest that the Ca²⁺-binding site is exposed on the inner surface of chromatophores, corresponding to the C-terminal region of LH1. An Asp-rich fragment in the LH1 α-polypeptide is considered to form a crucial part of the binding network. The slow response of LH1 Q _y transition upon exposure to EDTA is discussed in terms of the membrane environment in the chromatophores.     

The role of enoyl-CoA hydratase in the metabolism of isoleucine byPseudomonas putida

Chromatium vinosum, strain D, exhibits two extreme modifications of near infra-red absorption spectra when growing heterotrophically at temperatures either above or below 36.5° C. Chromatophores isolated from cells grown either at 33° C (33° C chromatophores) or 39° C (39° C chromatophores) were analyzed for structural and functional parameters. For this the following chromatophore subunits were solubilized and characterized; (i) a fraction absorbing maximally at 800 nm with shoulders at 820 and 850 nm when derived from 33° C chromatophores or absorbing at 800 nm and 850 nm when derived from 39° C chromatophores; (ii) reaction center-light harvesting bacteriochlorophyll complexes with identical spectra and ratios of reaction center to light harvesting bacteriochlorophyll (1:45); (iii) complexes containing cytochromes, (IV) reaction center bacteriochlorophyll complexes. Irrespective of their origins the fractions exhibited qualitatively identical protein patterns as analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis.Protein patterns of 33° C and 39° C chromatophores revealed an identical ratio of proteins of reaction centers to proteins of cytochrome preparations. But the ratio of proteins of reaction centers to proteins of light harvesting moieties was 1.9 times higher in 39° C chromatophores than in 33° C chromatophores. Correspondingly, the ratio of reaction center per total bacteriochlorophyll was 1.7 times higher in 39° C chromatophores (1:110) then in 33° C chromatophores (1:190). Activities of photophosphorylation were 0.73 and 0.56 moles of ATP per moles of total bacteriochlorophyll per min for 33° C and 39° C chromatophores, respectively. Activities of sulfide oxidation in the light by whole cells were 2.37 and 1.96 moles of sulfide per mole of total bacteriochlorophyll per min for 33° C and 39° C cells. Accordingly, on a reaction center basis activities are significantly lower after growth of the organisms at 39° C than at 33° C. The data indicate that spectral changes in Chromatium vinosum represent changes in the ratio of reaction center to light harvesting bacteriochlorophyll accompanied by a variation of the absorption spectra of the latter bacteriochlorophyll moiety. Concomitantly, activities coupled to the photochemical apparatus were subjected to variations.Abbreviations Bchl Bacteriochlorophyll - LDAO lauryl dimethylamine oxide - SDS sodium dodecyl sulfate