Complete assimilation of cysteine by a newly isolated non-sulfur purple bacterium resembling Rhodovulum sulfidophilum (Rhodobacter sulfidophilus)

A rod-shaped, motile, phototrophic bacterium, strain SiCys, was enriched and isolated from a marine microbial mat, with cysteine as sole substrate. During phototrophic anaerobic growth with cysteine, sulfide was produced as an intermediate, which was subsequently oxidized to sulfate. The molar growth yield with cysteine was 103 g mol^–1, in accordance with complete assimilation of electrons from the carbon and the sulfur moiety into cell material. Growth yields with alanine and serine were proportionally lower. Thiosulfate, sulfide, hydrogen, and several organic compounds were used as electron donors in the light, whereas cystine, sulfite, or elemental sulfur did not support phototrophic anaerobic growth. Aerobic growth in the dark was possible with fructose as substrate. Cultures of strain SiCys were yellowish-brown in color and contained bacteriochlorophyll a, spheroidene, spheroidenone, and OH-spheroidene as major photosynthetic pigments. Taking the morphology, photosynthetic pigments, aerobic growth in the dark, and utilization of sulfide for phototrophic growth into account, strain SiCys was assigned to the genus Rhodovulum (formerly Rhodobacter) and tentatively classified as a strain of R. sulfidophilum. In cell-free extracts in the presence of pyridoxal phosphate, cysteine was converted to pyruvate and sulfide, which is characteristic for cysteine desulfhydrase activity (l-cystathionine γ-lyase, EC 4.4.1.1). Received: 15 December 1995 / Accepted: 1 April 1996     

The protein patterns of intracytoplasmic membranes and reaction center particles isolated fromRhodopseudomonas capsulata

Intracytoplasmic membranes of wild type strain 37 b 4 and mutant strains A1a car^-bchl^-, A1a car^-bchl⁺ ofRhodopseudomonas capsulata were isolated. The membrane proteins were solubilized and separated by polyacrylamide gel electrophoresis (methods of Takayamaet al., 1964; Weber and Osborn, 1969). The band patterns were compared with each other. From the strain A1a car^-bchl⁺ reaction center particles were isolated by treatment of membrane with Triton X-100 followed by sucrose density gradient centrifugation. The reaction center particles were found to be enriched in reaction center bacteriochlorophyll. This pigment shows a reversible bleaching at 855 nm and a blue shift at 798 nm. The light harvesting bacteriochlorophyll portion of this fraction was 14–22% of the total bacteriochlorophyll content. The three main proteins of the reaction center particles amount to about 80% of the total protein of the particles. The molecular weights of the main proteins were estimated to be 32000, 27500 and 22500 daltons.     

The formation of bacteriochlorophyll · protein complexes of the photosynthetic apparatus of Rhodopseudomonas capsulata during early stages of development

Cells of Rhodopseudomonas capsulata cultivated at an oxygen partial pressure of 400 mmHg in the dark contained 0.1 nmol or less total bacteriochlorophyll per mg membrane protein. The bacteriochlorophyll was found in the reaction center (10 pmol bacteriochlorophyll/mg membrane protein) and in the light harvesting bacteriochlorophyll I but not in the light harvesting bacteriochlorophyll II. Formation of the photosynthetic apparatus in those cells was induced by incubation at a very low oxygen tension in the dark. Reaction center bacteriochlorophyll and light harvesting bacteriochlorophyll increased three fold after 60 min of incubation at 1–2 mmHg (pO₂). Light harvesting bacteriochlorophyll II increased strongly after 60 min and became dominating after 90 min of incubation. The total bacteriochlorophyll content doubled every 30 min, but synthesis of reaction center bacteriochlorophyll proceeded at much lower rates. Consequently the size of the photosynthetic unit (total bacteriochlorophyll/reaction center bacteriochlorophyll) increased from 15 to 52 during 150 min of incubation. The proteins of the photosynthetic apparatus were synthesized concomitantly with bacteriochlorophyll.Cells which were incubated at 0.5 mmHg (pO₂) do not grow but form the photosynthetic apparatus. During the first hours of incubation light harvesting bacteriochlorophyll I and reaction center bacteriochlorophyll were the dominant bacteriochlorophyll species, but light harvesting bacteriochlorophyll II was synthesized only in small amounts. Total bacteriochlorophyll and reaction center bacteriochlorophyll increased from 30 min up until 210 min of incubation more than 10 fold. The final concentrations of total bacteriochlorophyll and reaction center bacteriochlorophyll were 8.6 nmol and 0.26 nmol per mg membrane protein, respectively. The three protein components of the reaction centers (mol. wts. 28 000, 24 000 and 21 000) and the protein of the light harvesting I complex (mol. wt. 12 000) were incorporated simultaneously. The protein of band 1 (mol. wt. 14 000) which was present in the isolated light harvesting complex II, was synthesized only in very small amounts. The proteins of bands 3 and 4 (mol. wt. 10 000 and 8000) however, which were shown to be associated with light harvesting bacteriochlorophyll II, were synthesized in noticeable amounts as was light harvesting bacteriochlorophyll II. In addition a protein with an apparent molecular weight of 45 000 showed a strong incorporation of ¹⁴C-labeled amino acids. This protein comigrates with one protein which was found to be associated with a green pigment excreted during incubation at 0.5 Torr into the medium. The in vivo-absorption maxima of this pigment complex were 660, 590, 540, 417 and 400 nm. The succinate oxidase and the NADH oxidase seemed to be incorporated into the newly formed intracytoplasmic membrane only in very small amounts. Thus, reaction center and light harvesting bacteriochlorophyll and their associated proteins were simultaneously synthesized, whereas light harvesting complex II is the variable part of the photosynthetic apparatus.     

A new purple sulfur bacterium from stratified freshwater lakes,Amoebobacter purpureus sp. nov.

Six strains of a new purple sulfur bacterium were isolated from the chemocline of four different freshwater lakes. Single cells were spherical to oval, nonmotile and contained gas vacuoles in the central part of the cytoplasm. All strains contained bacteriochlorophyll a and okenone as the major carotenoid. The intracytoplasmic membrane system was of vesicular type. All strains resembled each other in growth conditions and utilization of simple organic carbon sources. The strains were able to grow microaerophilic in the dark, used hydrogen sulfide, elemental sulfur or thiosulfate as electron donor, and lacked assimilatory sulfate reduction. On the basis of all characteristics the new bacterium represents a new species of the genus Amoebobacter, A. purpureus sp. nov.     

Isolation and Characterization of a Pseudomonas putida Strain able to Grow with Trimethyl-1,2-dihydroxy-propyl-ammonium as Sole Source of Carbon, Energy and Nitrogen

Trimethyl-1,2-dihydroxypropyl-ammonium (TM) originates from the hydrolysis of the parent esterquat surfactant, which is widely used as softener in fabric care. Based on test procedures mimicking complex biological systems, TM is supposed to degrade completely when reaching the environment. However, no organisms able to degrade TM were isolated nor has the degradation pathway been elucidated so far. We isolated a Gram-negative rod able to grow with TM as sole source of carbon, energy and nitrogen. The strain reached a maximum specific growth rate of 0.4 h^–1 when growing with TM as the sole source of carbon, energy and nitrogen. TM was degraded to completion and surplus nitrogen was excreted as ammonium into the growth medium. A high percentage of the carbon in TM (68% in continuous culture and 60% in batch culture) was combusted to CO₂ resulting in a low yield of 0.54 mg cell dry weight per mg carbon during continuous cultivation and 0.73 mg cell dry weight per mg carbon in batch cultures. Choline, a natural structurally related compound, served as a growth substrate, whereas a couple of similar other quaternary aminoalcohols also used in softeners did not. The isolated bacterium was identified by 16S-rDNA sequencing as a strain of Pseudomonas putida with a difference of only one base pair to P. putida DSM 291^T. Despite their high identity, the reference strain P. putida DSM 291^T was not able to grow with TM and the two strains differed even in shape when growing on the same medium. This is the first microbial isolate able to degrade a quaternary ammonium softener head group to completion. Previously described strains growing on quaternary ammonium surfactants (decyltrimethylammonium, hexadecyltrimethylammonium and didecyldimethylammonium) either excreted metabolites or a consortium of bacteria was required for complete degradation.     

Occurrence of cytochrome c-554 in a facultative methylotroph,Protaminobacter ruber strain NR-1, during bacteriochlorophyll formation

A facultative methylotroph, Protaminobacter ruber was grown under two different conditions (aerobically grown under light, and aerobically in the dark after a light period). Bacteriochlorophyll was synthesized inducibly in the cells which were initially grown in the ligt and then grown in the dark, while bacteriochlorophyll was not found in the cells cultured under continuous light. Cytochrome c-554 was solely synthesized parallel to bacteriochlorophyll after switching from light to dark conditions. Both cytochrome c-554 and bacteriochlorophyll levels in the membrane preparation reached to a plateau in 24 h after switching from light and dark conditions. This cytochrome was membrane-bound and its M _r was 45,000 by sodium dodecylsulfate polyacrylamide gel electrophoresis. The midpoint potential was 358 mV at pH 7. Other major membrane-bound cytochromes and two soluble cytochromes were present in both types of cells and their content did not change irrespective of growth conditions.Abbreviations SDS-PAGE sodium dodecylsulfate polyacrylamide gel electrophoresis - Bchl bacteriochlorophyll     

Secretion of the overproduced periplasmic PhoA protein into the medium and accumulation of its precursor in phoA-transformed Escherichia coli strains: involvement of outer membrane vesicles

Various Escherichia coli strains were transformed by multicopy plasmids pHI-1, pHI-7 and pPHOI carrying the entire regulatory and structural phoA sequences. All transformants with the intact pho regulatory system displayed PhoA oversynthesis and secretion into the medium. They also accumulated the alkaline phosphatase precursor localized in the outer membrane fraction. The dynamics of enzyme synthesis and secretion as well as cell cytomorphology during secretion were studied in strain E. coli K12 802 carrying pHI-7 plasmid. PhoA protein was shown to be selectively released into the medium in vesicles budding from outer membrane.The authors are with the institute of Biochemistry and Physiology of Microorganisms, USSR Academy of Sciences, 142292 Puschino, Moscow Region, USSR.     

The early formation of the photosynthetic apparatus in Rhodospirillum rubrum

The time dependent assembly of the photosynthetic apparatus was studied in Rhodospirillum rubrum after transfer of cells growing aerobically in the dark to low aeration. While bacteriochlorophyll (Bchl) cellular levels increase continuously levels of soluble cytochrome c ₂do not change significantly. Absorption spectra of membranes isolated at different times after transfer reveal that incorporation of carotenoids lags behind incorporation of Bchl. However, a carotenoid fraction exhibiting spectral properties of spirilloxanthin isomers was isolated apart from membranes. This carotenoid fraction even was present in homogenates from Bchl-free, aerobically grown cells. Incorporation of U-¹⁴C-proteinhydrolyzate into membrane proteins showed that proteins are mainly formed which are specific for photosynthetic membranes. Although the proportion of reaction center (RC) Bchl per light harvesting (LH) Bchl does not change the proportions of membrane proteins present in RC and LH preparations change initially. But later on the proportions of the different proteins also reach constant values. Concerning proteins characteristic for cytoplasmic membranes a differential incorporation of label can be observed. The data indicate that the photosynthetic apparatus in Rhodospirillum rubrum is assembled through a sequential mechanism.Abbreviations Bchl bacteriochlorophyll - LH light harvesting - RC reaction center - R. Rhodospirillum - R. Rhodopseudomonas     

Characterization of a new platelet-forming purple sulfur bacterium,Amoebobacter pedioformis sp. nov.

The dominant purple sulfur bacterium of a reddish-colored waste water pond near Taichung, Taiwan, was isolated in pure culture, strain CML2. Individual cells were nearly spherical, nonmotile, and contained in their peripheral parts was vacuoles that appeared like elongated, curved tubes. Four to sixteen cells formed platelet-like aggregates reminiscent of Thiopedia rosea. The intracellular photosynthetic membrane system of the cells was of vesicular type; the photosynthetic pigments consisted of bacteriochlorophyll a and spirilloxanthin as the major carotenoid. The color of cell suspensions was pink to rosered. Under anaerobic conditions photolithoautotrophic growth occurred with sulfide, elemental sulfur or thiosulfate; sulfur globules were stored as an intermediary oxidation product. In the presence of sulfide, acetate, lactate and pyruvate were photoassimilated; strain CML2 lacked assimilatory sulfate reduction. Fastest photoautotrophic growth (11 h doubling time) was obtained at pH 7.5, 35°C and a light intensity of about 1000 lux (tungsten lamp). Chemolithoautotrophic growth in the dark was possible under reduced oxygen partial pressure with reduced sulfur compounds as respiratory substrates. The DNA base composition of strain CML2 was 65.5 mol% G+C. Strain CML2 is described as type strain of a new species, Amoebobacter pedioformis sp. nov., in the family Chromatiaceae.     

<Emphasis Type="Italic">Chromocurvus halotolerans</Emphasis> gen. nov., sp. nov., a gammaproteobacterial obligately aerobic anoxygenic phototroph,isolated from a Canadian hypersaline spring

A strain EG19^T of aerobic bacteria able to form pleomorphic cells was isolated from a brine spring runoff stream in the west central region of the province of Manitoba, Canada. The pale pinkish purple strain contained bacteriochlorophyll a incorporated into light-harvesting I and reaction center complexes. Its inability to grow under anaerobic illuminated conditions prompted designation as a member of the functional group known as aerobic anoxygenic phototrophic bacteria. Phylogenetic analysis of the 16S rRNA gene sequence revealed that it belonged to the Gammaproteobacteria, forming a distinct branch of phototrophs distantly related to most described aerobic anoxygenic phototrophs, quite marginally related (95.6%) both to the only other described gammaproteobacterial aerobic phototroph, Congregibacter litoralis, and also to nonphototrophs in the genus Haliea (95.1–96.1%). Physiological tests demonstrated tolerance profiles to salinity (0–18% NaCl), pH (7–12), and temperature (7–40°C) consistent with survival in a shallow hypersaline stream on the exposed, vegetation-depleted salt playa of its native East German Creek. Phylogenetic data and phenotypic properties such as pigment composition, morphology, and physiology support the proposal of the novel genus and species Chromocurvus halotolerans gen. nov., sp. nov., with EG19^T (=DSM 23344^T, =VKM B-2659^T) as the type strain.     

Bacteriochlorophyll, Fatty-Acid, and Protein Synthesis in Relation to Thylakoid Formation in Mutant Strains of Rhodospirillum rubrum

Mutant strains of Rhodospirillum rubrum are isolated which are blocked in different stages of pigment synthesis. In these strains the morphogenesis of thylakoids and the pigment production are investigated. Concerning bacteriochlorophyll synthesis two groups of mutants are separable. The members of the first group synthesize bacteriochlorophyll. Some of these mutants excrete bacteriopheophytin. The strains of the second group are not able to synthesize bacteriochlorophyll. Members of both groups excrete bacteriochlorophyll precursors into the cultural medium. These pigments were identified by their spectral properties as Mg-2,4-divinyl-pheoporphyrin a(5)-monomethylester, pheophorbide a, and 2-devinyl-2-hydroxyethyl-pheophorbide a. Thylakoids are only formed by those strains which are able to synthesize bacteriochlorophyll. However, small amounts of bacteriochlorophyll can be produced without a concomitant thylakoid synthesis. The fatty-acid pattern in some mutants is modified quantitatively. However, the results do not indicate any correlation between disturbance of thylakoid morphogenesis and a deviation of fatty-acid composition. Fatty acids seem to have no special functions in thylakoid morphogenesis. The membranes of the mutants were isolated, split into protein subunits, and these were separated by disc electrophoresis. A characteristic protein pattern, first of all a high content of fraction E, is correlated with the ability to form thylakoids. In addition, all mutants which synthesize bacteriochlorophyll contain a fast-migrating membrane protein (zone G). The results suggest that the whole bacteriochlorophyll-protein complex is necessary for thylakoid formation.     

Characterization and Properties of a Protochlorophyllide Ester in Leaves of Dark Grown Barley with Geranylgeraniol as Esterifying Alcohol

The protochlorophyllide ester isolated from dark grown barley leaves was shown to contain geranylgeraniol as esterifying alcohol. No phytylester was found. The qualitative analyses were performed with combined gas chromatography-mass spec-trometry. Chromatographic separation and spectrofluorometric determination of the protochlorophyll and chlorophyll pigments before and after irradiation of the dark grown leaves with light flashes at 2°C showed that part of the protochlorophyllide ester was photoconverted to chlorophyll a.     

Selective enrichment and characterization of Roseospirillum parvum, gen. nov. and sp. nov., a new purple nonsulfur bacterium with unusual light absorption properties

A new type of phototrophic purple bacterium, strain 930I, was isolated from a microbial mat covering intertidal sandy sediments of Great Sippewissett Salt Marsh (Woods Hole, Mass., USA). The bacterium could only be enriched at a wavelength of 932 (± 10) nm. Cells were vibrioid- to spirilloid-shaped and motile by means of bipolar monotrichous flagellation. The intracytoplasmic membranes were of the lamellar type. Photosynthetic pigments comprised bacteriochlorophyll a and the carotenoids spirilloxanthin and lycopenal. The isolated strain exhibited an unusual, long-wavelength absorption maximum at 911 nm. Sulfide or thiosulfate served as electron donor for anoxygenic phototrophic growth. During growth on sulfide, elemental sulfur globules formed outside the cells. Elemental sulfur could not be further oxidized to sulfate. In the presence of sulfide plus bicarbonate, fructose, acetate, propionate, butyrate, valerate, 2-oxoglutarate, pyruvate, lactate, malate, succinate, fumarate, malonate, casamino acids, yeast extract, L(+)-alanine, and L(+)-glutamate were assimilated. Sulfide, thiosulfate, or elemental sulfur served as a reduced sulfur source for photosynthetic growth. Maximum growth rates were obtained at pH 7.9, 30 °C, 50 μmol quanta m^–2 s^–1 of daylight fluorescent tubes, and a salinity of 1–2% NaCl. The strain grew microaerophilically in the dark at a partial pressure of 1 kPa O₂. The DNA base composition was 71.2 mol% G + C. Sequence comparison of 16S rRNA genes indicated that the isolate is a member of the α-Proteobacteria and is most closely related to Rhodobium orientis at a similarity level of 93.5%. Because of the large phylogenetic distance to known phototrophic species of the α-Proteobacteria and of its unique absorption spectrum, strain 930I is described as a new genus and species, Roseospirillum parvum gen. nov. and sp. nov. Received: 29 December 1998 / Accepted: 17 March 1999     

Biochemical Properties of A Thermophilic Alkalophile

A thermophilic alkalophile (IC strain) which can grow well in an alkaline medium at over 55°C was isolated from soil samples, and identified as Bacillus licheniformis; its growth on a neutral medium was, however, very poor. This strain was able to grow at 37°C as well as at 55°C, but the specific growth rate at 55°C was about twice as high as that at 37°C under alkaliné conditions.

The intracellular pH remained below 9.5 when Na⁺ was present in the medium. Na ⁺ stimulated the alanine uptake by cells or membrane vesicles, but was not required ATP synthesis.

Intracellular enzymes were stable on heat treatment up to 60°C. The residual activity of enolase after heating at 60°C for 10 min was about 80%. Cytochrome oxidase in membrane vesicles was completely stable up to 58°C for 30 min. These enzymes were also resistant to SDS treatment, more than 50% of their activities remaining at 5% SDS.     

Biosynthesis in isolatedAcetabularia chloroplasts II. Plastid pigments

Summary The plastid pigments — chlorophylls and carotenoids — of the alga,Acetabularia, have been chromatographically separated and identified. These pigments were found to become radio-active during incubations of an isolated chloroplast fraction with¹⁴CO₂. Specific activity calculations indicate that appreciable amounts of synthesis were occurringin vitro. The phytol and porphyrin moieties of chlorophyll a were both radioactive; thus the pigments were being formed completely from recent photosynthetic products. A comparison of the incorporation of¹⁴CO₂ into plastid pigmentsin vivo andin vitro suggests that the isolated chloroplasts form the pigments at their normalin vivo rates.     

Cloning of phoM, a gene involved in regulation of the synthesis of phosphate limitation inducible proteins in Escherichia coli K12

Summary Like the synthesis of alkaline phosphatase, the synthesis of outer membrane PhoE protein is shown to be dependent on the phoM gene product in phoR mutants of E. coli K12. This phoM gene has been cloned into the multicopy vector pACYC184 using selection for alkaline phosphatase constitutive synthesis in a phoR background. The gene was localized on the hybrid plasmids by analysis of deletion plasmids constructed in vitro and of mutant plasmids generated by insertions.Interestingly, two of the selected hybrid plasmids contained the entire phoA-phoB-phoR region of the chromosome, as a multiple copy state of these genes results in the constitutive synthesis of alkaline phosphatase. The presence of multiple copies of the phoM gene hardly influences the level of expression of alkaline phosphatase and PhoE protein in a pho ⁺ strain, but significantly increases the levels of these proteins in aphoR mutant strain.     

Periodicity in cell division and physiological behavior of ditylum brightwellii,a marine planktonic diatom,during growth in light-dark cycles

Summary Cells of Ditylum brightwellii, a large marine centric diatom, were partially synchronized by employing an appropriate light-dark cycle. At 20°C this consisted of 8 hrs of illumination at an intensity of 0.05 cal/cm² min. A single 2.8 l culture was studied over a 20 day period by diluting the culture daily to a standard cell concentration. The sequence of events in cell development was as follows: daughter cells were formed late in the light period, in the dark they elongated and the numerous chromatophores began dividing. A minimum cell buoyancy was observed in the dark concurrent with cell elongation. Increase in cell phosphorus took place in the dark period. The photosynthetic rate of cells removed during the dark period decreased to a minimum. In the following light period photosynthetic rate increased to a maximum, photosynthetic pigments, cell carbon, nitrogen, and carbohydrate increased and cell division again took place. Cell silica content increased concomitant with cell division. Details of cell morphology during cell division, based upon light microscopy, are reported.Contribution of the Scripps Institution of Oceanography.     

A 4-vinylprotochlorophyllide complex accumulated by “phofil” mutant of Rhodopseudomonas spheroides. An authentic intermediate in the development of the photosynthetic apparatus

A photosynthetically competent mutant strain of Rhodopseudomonas spheroides was isolated. In addition to bacteriochlorophyll, this organism produced particle-bound precursor 4-vinylprotochlorophyllide. The spectral characteristics of the pigment complex(es) accumulated in the culture medium were very variable. The spectral form occurring within the bacteria was characterized from fluorescence data. Its particle weight, 130 000, was determined by Sephadex G200 filtration. The main components of the complex were protein, lipid and pigment (6.8 : 6 : 1, w/w). As indicated by qualitative analysis, the lipid components were characteristic constituents of the photosynthetic membrane.Kinetics of pigments synthesis showed that the total pigment synthesis was not affected by the mutation; bacteriochlorophyll content was always lower in the mutant than in the parent strain. The repigmentation process was followed by fluorescence emission. The results indicated that the mutation affected membrane component synthesis required for the bacteriochlorophyll(ide) incorporation.The pigment complex was concluded to be an authentic intermediate in photosynthetic apparatus morphogenesis. The reasons for its excretion are discussed.     

Impact of light/dark regimen on growth rate,biomass formation and bacteriochlorophyll synthesis in Erythromicrobium hydrolyticum

The impact of illumination on specific growth rate, biomass formation, and synthesis of photopigment was studied in Erythromicrobium hydrolyticum, an obligately aerobic heterotrophic bacterium having the ability to synthesize bacteriochlorophyll a. In dark-grown continuous cultures the concentration of protein increased with increasing dilution rate, the concentration of bacteriochlorophyll a showed the opposite effect. At a dilution rate of 0.08 h^-1 (68% of _max in the dark) and S_R-acetate of 11.8 mM, the concentration of BChla of illuminated cultures in steady-state was 11–22 nM, compared to 230–241 nM in cultures incubated in darkness. No significant differences were observed in the concentration of protein. A shift from darkness to light conditions resulted in increased specific growth rates resulting in increased biomass formation, thus showing that light enhances growth by serving as an additional energy source. This phenomenon, however, was temporary because bacteriochlorophyll synthesis is inhibited by light. In contrast to incubation in continuous light or dark, incubation under light/dark regimen resulted in permanently enhanced biomass formation. In the dark periods, bacteriochlorophyll was synthesized at elevated rates (compared to constant darkness), thus compensating the inhibitory effect of light in the preceding period. It thus appears that the organism is well-adpated to life in environments with alternating light/dark conditions. The ecological relevance of the observations is discussed.Non-standard abbreviations BChla bacteriochlorophyll a - D dilution rate - spceific growth rate - K_s saturation constant - S_R concentration of limiting in inflowing medium of chemostat     

Die Ausscheidung von partikelgebundenen Bacteriochlorophyllvorstufen durch die Mutante F9 von Rhodospirillum rubrum

Zusammenfassung Eine bacteriochlorophyllfreie Mutante von Rhodospirillum rubrum wird beschrieben. Diese Mutante scheidet die Bacteriochlorophyllvorstufen Phaeophorbid a und 2-Devinyl-2--Hydroxyäthyl-Phaeophorbid a unter semiaeroben Bedingungen in das Kulturmedium aus. Beide Pigmente sind mit einem Trägermolekül zu einem Komplex verbunden. Die Analyse des Komplexes ergab folgende Zusammensetzung: 49% Protein, 30% Pigment, 11% Lipide, 3% Zucker, sowie eine geringe Menge Phosphor (0,2%). Die Aminosäurezusammensetzung des Proteinanteils wird angegeben. Die Fettsäuren werden gaschromatographisch bestimmt. Die Zuckerkomponente ist anders zusammengesetzt als das Lipopolysaccharid aus Rhodospirillum rubrum. Das Molekulargewicht der kleinsten Proteinuntereinheit beträgt 16500, das Molekulargewicht des Pigmentkomplexes ergibt sich daraus mit 34000. Typische Thylakoide werden in der Mutante nicht ausgebildet. Die Notwendigkeit einer ungestört ablaufenden Bacteriochlorophyllsynthese für die normale Thylakoidmorphogenese wird diskutiert.

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The production of particle bound bacteriochlorophyll precursors by the mutant F9 of Rhodospirillum rubrum

Summary A mutant strain of Rhodospirillum rubrum is described which does not form bacteriochlorophyll. This mutant strain excretes the bacteriochlorophyll precursors pheophorbide a and 2-devinyl-2-hydroxyethylpheophorbide a into the cultural medium, when it is cultured under low aeration in the dark. The pigments were identified spectroscopically. Both of the pigments are bound to a macromolecular compound. The complete macromolecule was shown to be composed of 49% protein, 30% pigments, 11% lipid, 3% sugar, and a trace of phosphorus (0.2%). The amino acid composition of the protein as well as the fatty acid pattern of the lipid are presented. The percent portions of fatty acids in whole cells are quite different from that of the pigment complex. The composition of the sugar moiety was demonstrated to be different from that of the lipopolysaccharide of Rhodospirillum rubrum. The molecular weight of the smallest subunit of the protein is 16,500. This suggests a molecular weight of 34,000 for the total pigment complex. Typical thylakoids were not observed in cells of the mutant strain. The necessity of an unblocked bacteriochlorophyll synthesis for the normal thylakoid morphogenesis is discussed.