Homologies in processing and sequence between the 23S ribosomal ribonucleic acids of Paracoccus denitrificans and Rhodopseudomonas sphaeroides

We have shown that mature 50S ribosomal subunits of Paracoccus denitrificans lack intact 23S rRNA, containing instead rRNAs of 0.56 (16S) and 0.37 (14S)x10⁶ molecular weight. Kinetic labelling studies showed these to be derived from a 1.02x10⁶ dalton precursor, which may itself derive from a larger and very transient 23S species. A similar pattern of rRNA processing has been previously described for Rhodopseudomonas sphaeroides, and we have compared, by Tl oligonucleotide catalog analysis, the smaller (14S) fragments of P. denitrificans and R. sphaeroides 23S rRNAs. These were shown to exhibit strong sequence homology, and comparisons of 14S-derived oligonucleotides to oligonucleotides from an in vitro-generated 13S fragment of Escherichia coli 23S rRNA suggest that P. denitrificans and R. sphaeroides 14S rRNAs arise from the 5-terminal portions of their respective 23S precursors. Results are considered to be consistent with the claim that P. denitrificans arose, by loss of photophosphorylation, from a member of the Rhodospirillaceae.Abbreviations E buffer 60 ml 2 M Tris base, 20 ml 3 M sodium acetate, 15 ml 0.2M disodium EDTA, 6 ml glacial acetic acid, 900 ml distilled water - HEPES N-2-hydroxymethyl piperazine-N-2-ethanesulfonic acid - TMK 5 mM Tris-Cl, 0.1 mM MgSO₄, 60 mM KCl. pH 7.3 - TM3 10 mM Tris-Cl, 1 mM MgCl₂, pH 7.3 - Tris tris (hydroxymethyl) aminomethane - SDS sodium dodecyl sulphate     

A Kdp-like,high-affinity,K+-translocating ATPase is expressed during growth of Rhodobacter sphaeroides in low potassium media

Cells of the purple non-sulphur bacterium Rhodobacter sphaeroides express a high-affinity K⁺ uptake system when grown in media with low K⁺ concentrations. Antibodies againts the catalytic KdpB protein or the whole KdpABC complex of Escherichia coli crossreact with a 70.0 kDa R. sphaeroides protein that was expressed only in cells grown in media with low K⁺ concentrations. In membranes derived from R. sphaeroides cells grown with low K⁺ concentrations (induced cells), a high ATPase activity could be detected when assayed in Tris-HCl pH 8.0 containing 1 mM MgSO₄. This ATPase activity increased upon addition of 1 mM KCl from 166 to 289 mol ATP hydrolysed x min^-1 x g protein^-1 (1.7-fold stimulation). The K⁺-stimulated ATPase activity was inhibited approximately 93% by 0.5 mM vanadate but hardly by N,N-dicyclohexylcarbo-diimide (DCCD). These results indicate that the inducible K⁺-ATPase in R. sphaeroides resembles the Kdp K⁺-translocating ATPase of Escherichia coli. This Kdp-like transport system is also expressed in R. capsulatus and Rhodospirillum rubrum during growth in media with low K⁺ concentrations suggesting a wide distribution of this transport system among phototrophic bacteria.Abbreviations electrical potential difference across the cytoplasmic membrane - pH pH difference across the cytoplasmic membrane - BSA bovine serum albumine - PAGE polyacrylamide gel electrophoresis - HEPES 4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid - PMSF phenyl-methyl-sulfonyl fluoride - DCCD N,N-dicyclohexylcarbodiimide - AIB 2--aminoisobutyric acid - TMG methyl--d-thiogalactopyranoside     

Proton translocation during denitrification in Rhodopseudomonas sphaeroides f. denitrificans

Proton translocation during the reduction of NO ₃ ^- , NO ₂ ^- , N₂O and O₂, with endogenous substrates, in washed cells of Rhodopseudomonas sphaeroides f. denitrificans was investigated by an oxidant pulse method. On adding NO ₂ ^- to washed cells, anaerobically in the dark, an alkalinization occurred in the reaction mixture followed by acidification. When NO ₃ ^- , N₂O or O₂ was added to cells in the dark or with these compounds and NO ₂ ^- in light an acidification only was observed. Proton translocation was inhibited by carbonyl cyanide-m-chlorophenyl hydrazone.Valinomycin treated cells produced acid in response to the addition of either NO ₃ ^- , NO ₂ ^- , N₂O or O₂. The proton extrusion stoichiometry ( ratios) in illuminated cells were as follows: NO ₃ ^- 0.5N₂, 4.82; NO ₂ ^- 0.5N₂, 5.43; N₂ON₂, 6.20; and O₂H₂O, 6.43. In the dark the comparable values were 3.99, 4.10, 4.17 and 3.95. Thus, illuminated cells produced higher values than those in the dark, indicating a close link between photosynthesis and denitrification in the generation of proton gradients across the bacterial cell membranes.When reduced benzyl viologen was the electron donor in the presence of 1 mM N-ethylmaleimide and 0.5 mM 2-n-heptyl-4-hydroxyquinoline-N-oxide in the dark, the addition of either NO ₃ ^- , NO ₂ ^- or N₂O to washed cells resulted in a rapid alkalinization of the reaction mixture. The stoichiometries for proton consumption, ratios without a permeant ion were NO ₃ ^- NO ₂ ^- ,-1.95; NO ₂ ^- 0.5 N₂O,-3.03 and N₂ON₂,-2.02. The data indicate that these reductions occur on the periplasmic side of the cytoplasmic membrane.Abbreviations BVH reduced benzyl viologen - CCCP carbonyl cyanide m-chlorophenyl hydrazone - DIECA N, N-diethyl-dithiocarbamate - HOQNO 2-n-heptyl-4-hydroxyquinoline-N-oxide - NEM N-ethylmaleimide     

Augmentation of H2 photoproduction in Rhodopseudomonas palustris by N-heterocyclic aromatic compounds

Increases of 23- (5.6 mmol acetylene reduced mg dry wt^–1) and 16- (4 mmol acetylene reduced mg dry wt^–1) fold in nitrogenase activity and 12- (671 l H₂ mg dry wt^–1 h^–1) and 6- (349 l mg dry wt^–1 h^–1) fold in H₂ photoproduction in Rhodopseudomonas palustris JA1 over 24 h were achieved with pyrazine 2-carboxylate (3 mM) and 3-picoline (3 mM), respectively, and were higher than earlier reports of enhancement (1.5 to 5- fold) in biological H₂ production using various alternative methods.     

Active transport of proline into washed cells of Rhodopseudomonas sphaeroides f. sp. denitrificans grown with nitrate

Washed cells of Rhodopseudomonas sphaeroides f. sp. denitrificans, prepared from cultures grown anaerobically in light with NO ₃ ^- as the terminal acceptor, readily incorporated [¹⁴C]-proline both in light and in the dark. The proline uptake was coupled to the reduction of either NO ₃ ^- , NO ₂ ^- , N₂O or O₂. Light stimulated the accumulation of proline in these cells. The addition of NO ₃ ^- to washed cells in light decreased the K _m for proline from 40 M to 5.7 M. Proline transport was inhibited by antimycin A, 2-n-heptyl-4-hydroxyquinoline-N-oxide both in light and in the dark with nitrate indicating that electron transfer from both denitrification and photosynthesis are involved in this uptake. Inhibition by carbonyl cyanide-m-chlorophenyl hydrazone and 2.4-dinitrophenol indicate that proline transport is energy dependent. The H⁺/proline stoichiometry increased from 1 to 2.5 when the external pH was increased from 6.0 to 8.0. Under these conditions pro increased but p decreased markedly above pH 7.0.Abbreviations TPP⁺ Tetraphenylphosphonium bromide - EDTA ethylenediamine-tetra-acetic acid - CCCP carbonyl cyanide-m-chlorophenyl hydrazone - DNP 2,4-dinitrophenol - HOQNO 2-n-heptyl-4-hydroxyquinoline-N-oxide - DBMIB dibromo-methyl-isopropyl-p-benzoquinone - DCCD N,N-dicyclohexylcarbodiimide     

Ammonium uptake in Rhodopseudomonas capsulata

Investigations of the uptake of ammonium (NH ₄ ⁺ ) by Rhodopseudomonas capsulata B100 supported the presence of an NH ₄ ⁺ transport system. Experimentally NH ₄ ⁺ was determined by electrode or indophenol assay and saturation kinetics were observed with two apparent K _m's of 1.7 M and 11.1 M (pH 6.8, 30°) and a V _max at saturation of 50–60 nmol/min·mg protein. The optimum pH and temperature were 7.0 and 33° C, respectively. The Q₁₀ quotient was calculated to be 1.9 at 100 M NH ₄ ⁺ , indicating enzymatic involvement. In contrast to the wild type, B100, excretion of NH ₄ ⁺ , not uptake, was observed in a glutamine auxotroph, R. capsulata G29, which is derepressed for nitrogenase and lacks glutamine synthetase activity. G29R1, a revertant of G29, also took up NH ₄ ⁺ at the same rate as wild type and had fully restored glutamine synthetase activity. Partially restored derivatives, G29R5 and G29R6, grew more slowly than wild type on NH ₄ ⁺ as the nitrogen source, remained derepressed for nitrogenase in the presence of NH ₄ ⁺ , and displayed rates of NH ₄ ⁺ uptake in proportion to their glutamine synthetase activity. Ammonium uptake and glutamine synthetase activity were also restored in R. capsulata G29 exconjugants which had received the plasmid pPS25, containing the R. capsulata glutamine synthetase structural gene. These data suggest that NH ₄ ⁺ transport is tightly coupled to assimilation.Abbreviations used CHES cyclohexylaminoethanesulfonic acid - GS glutamine synthetase - SDS sodium dodecylsulfate     

The close phylogenetic relationship of Nitrobacter and Rhodopseudomonas palustris

The phylogenetic position of Nitrobacter winogradskyi and two other nitrite-oxidizing bacteria was elucidated comparing oligonucleotides of the 16S ribosomal RNA. Nitrobacter winogradskyi and the Nitrobacter isolate Yukatan are genetically nearly identical; Nitrobacter isolate X14 is more distantly related. Phylogenetically, Nitrobacter is a member of a group of purple non-sulfur bacteria that is defined by various species of Rhodopseudomonas, Rhodomicrobium vannielii, Rhodospirillum rubum and their non-phototrophic relatives. Nitrobacter shares a high sequence similarity to Rhodopseudomonas palustris. These findings are in accord with several common taxonomic characteristics, and in addition support the conversion hypothesis for the origin of this group of chemolithotrophic bacteria.     

The enzymatic system thiosulfate: Cytochrome c oxidoreductase from photolithoautotrophically grown Rhodopseudomonas palustris

Rhodopseudomonas palustris cells, characterized by a lamellar type intracytoplasmic chromatophore membrane system after phototrophic growth, yielded a crude supernatant cell-free fraction (S-144) after ultracentrifugation which retained the contents of both the cell compartments. After thiosulfate-dependent growth, a protein system was isolated from S-144 which catalyzed the thiosulfate-linked reduction of an endogenous c-type cytochrome. — The colorless oxidoreductase protein, after purification to homogeneity, revealed a molecular weight of 93,000 and, after SDS treatment, a particle weight of 48,000. It was focused at an average pI of 5.45. Apparent K _m values for several substrates were in the M range. The electron acceptor for thiosulfate oxidation was found to be a cytochrome c from S-144. The homogeneous acceptor protein, at liquid nitrogen temperature, exhibited absorption maxima at 549.0, 518.5 and 418.0 nm, and shoulders at 525.5, 512.0 and 508.0 nm. Its molecular weight was found to be 17,000 (gel filtration) and 16,000 (SDS gel electrophoresis). It was characterized by a pI of 10.0. Its midpoint redox potential of E _m,7.0=+228 mV was determined by redox titrations and the value of +205 mV by spectrophotometric calculations.Abbreviations BSA bovine serum albumin - HiPIP high potential nonheme iron protein - IEF isoclectric focusing - SDS dodecylsulfate, sodium salt - Temed N,N,N,N-tetramethylethylenediamine     

Sulfate activation in Rhodobacter sulfidophilus and other species of the Rhodospirillaceae

Rhodobacter sulfidophilus, R. capsulatus, R. sphaeroides, Rhodospirillum rubrum, Rhodopseudomonas palustris, R. viridis and Rhodocyclus gelatinosus were found to be able to synthesize adenylylsulfate and 3-phosphoadenylylsulfate from sulfate and ATP. The presence of ATP sulfurylase was proven for the soluble protein fractions of all these species. ADP sulfurylase was not found. ATP sulfurylase was purified from R. sulfidophilus. Its molecular weight was 290,000. The enzyme is stabilized by magnesium ions and elevated salinities. The optimal pH was 8.0, activity was found between pH 6.8 and 9.4. The enzyme is inactivated at temperatures above 40°C. Kinetic studies resulted in K _m(ATP)=0.26 mM, K _m(sulfate)=0.33 mM; K _i(AMP)-2.1 mM, K _i(ADP)=1.15 mM; K _i(APS)=0.8 M; K _i(sulfite)=0.4. mM; K _i(sulfide)=0.66mM.Uncommon abbreviations APS adenylylsulfate - PAPS 3-phosphoadenylylsulfate - PEP phosphoenolpyruvate Dedicated to Professor Gerhart Drews on the occasion of his 60th birthday     

A comparison of electron transport and photophosphorylation systems of Rhodopseudomonas capsulata and Rhodospirillum rubrum

The photophosphorylation systems of Rhodopseudomonas capsulata and Rhodospirillum rubrum chromatophores have been compared in respect to the effects of artificial electron carries [N-methyl-phenazonium methosulfate (PMS) and diaminodurene], reducing agents (ascorbate in particular), and various quinones in the absence and presence of the electron transport inhibitors antimycin A and dibromothymoquinone (DBMIB). In addition, the effects of both inhibitors on photosynthetic electron transport through cytochromes b and c has been followed. From the results obtained, it appears that in both organisms: a) ubiquinone functions as an electron carrier between the cytochromes, and b) both antimycin A and DBMIB inhibit cyclic electron flow in the segment ... cytochrome bubiquinone»cytochrome c ..., but at different sites. The systems apparently differ mainly in respect to the nature of the electron flow by-pass shunt that is evoked in the presence of PMS; thus, in R. rubrum, PMS catalyzes a shunt that by-passes both cytochrome b and ubiquinone, whereas in Rps. capsulata the PMS shunt seems to circumvent only ubiquinone.Abbreviations BChl bacteriochlorophyll - DAD diaminodurene=2,3,5,6-tetramethyl-p-phenylenediamine - DBMIB dibromothymoquinone=2,5-dibromo-6-isopropyl-3-methylbenzoquinone - HOQNO heptylhydroxyquinoline-N-oxide - PMS N-methylphenazonium methosulfate     

Differences in the control of bacteriochlorophyll formation by light and oxygen

Control of bacteriochlorophyll formation was studied with continuous cultures of Rhodospirillum rubrum, Rhodopseudomonas sphaeroides, and Rhodopseudomonas capsulata. Oxygen controlled specific bacteriochlorophyll contents of the three species in a hyperbolical fashion irrespective of the presence of light. In Rps. sphaeroides, this applied to oxygen concentrations above 16% air saturation of the medium while at lower oxygen concentrations control followed a kinetics with negative cooperativity. Cell protein formation of R. rubrum and Rsp. sphaeroides was independent of oxygen concentrations while protein formation of Rps. capsulata increased at lower concentrations. Light controlled bacteriochlorphyll contents of R. rubrum and Rps. sphaeroides in a sigmoidal fashion. When growing at a constant low oxygen concentration cell protein formation increased with light energy flux in Rps. sphaeroides but remained unaffected in R. rubrum. Protein formation of R. rubrum increased with light energy flux only under anaerobic conditions. Two factor analyses were performed with R. rubrum and Rps. sphaeroides to study the combined effects of light and oxygen on bacteriochlorophyll formation. The results showed that both factors act independent of each other.Abbreviations ALA 5-aminolevulinic acid - R Rhodospirillum - Rsp. Rhodopseudomonas     

A tracked approach for automated NMR assignments in proteins (TATAPRO)

A novel automated approach for the sequence specific NMR assignments of ¹H^N, ¹³C, ¹³C, ¹³C/¹H and ¹⁵N spins in proteins, using triple resonance experimental data, is presented. The algorithm, TATAPRO (Tracked AuTomated Assignments in Proteins) utilizes the protein primary sequence and peak lists from a set of triple resonance spectra which correlate ¹H^N and ¹⁵N chemical shifts with those of ¹³C, ¹³C and ¹³C/¹H. The information derived from such correlations is used to create a `master_list' consisting of all possible sets of ¹H^N _i, ¹⁵N_i, ¹³C _i, ¹³C _i, ¹³C_i/¹H _i, ¹³C _i–1, ¹³C _i–1 and ¹³C_i–1/ ¹H _i–1 chemical shifts. On the basis of an extensive statistical analysis of ¹³C and ¹³C chemical shift data of proteins derived from the BioMagResBank (BMRB), it is shown that the 20 amino acid residues can be grouped into eight distinct categories, each of which is assigned a unique two-digit code. Such a code is used to tag individual sets of chemical shifts in the master_list and also to translate the protein primary sequence into an array called pps_array. The program then uses the master_list to search for neighbouring partners of a given amino acid residue along the polypeptide chain and sequentially assigns a maximum possible stretch of residues on either side. While doing so, each assigned residue is tracked in an array called assig_array, with the two-digit code assigned earlier. The assig_array is then mapped onto the pps_array for sequence specific resonance assignment. The program has been tested using experimental data on a calcium binding protein from Entamoeba histolytica (Eh-CaBP, 15 kDa) having substantial internal sequence homology and using published data on four other proteins in the molecular weight range of 18–42 kDa. In all the cases, nearly complete sequence specific resonance assignments (> 95%) are obtained. Furthermore, the reliability of the program has been tested by deleting sets of chemical shifts randomly from the master_list created for the test proteins.     

Purification and structural properties of adenylylated and deadenylylated glutamine synthetase from Rhodopseudomonas sphaeroides

Glutamine synthetase (GS) of Rhodopseudomonas sphaeroides is regulated by adenylylation and deadenylylation. The extent of adenylylation/deadenylylation of the enzyme in cell free extracts was influenced by inorganic phosphate (P _i), -ketoglutarate, ATP and other nucleotides. While P _i and -ketoglutarate stimulated deadenylylation, ATP and other nucleotides enhanced adenylylation of the GS. By using proper combinations of the effectors and incubation conditions, any desired adenylylation state of GS could be adjusted in vitro. The enzyme was purified to electrophoretic homogenity by three steps including affinity chromatography on 5-AMP-Sepharose. Adenylylated and deadenylylated enzyme showed different UV-spectra and isoelectric points. The native enzyme had a molecular weight of 600,000, deadenylylated subunits of 50,000±1,000. Electron microscopic investigations revealed a dodecameric arrangement of subunits in two hexameric planes.     

Photooxidase activity of isolated chromatophores and intact cells of phototrophic bacteria

Illumination causes an uptake of oxygen by isolated chromatophores of purple and green bacteria incubated with electron donors. Photooxidase activity of Rhodospirillum rubrum, Chromatium minutissimum, Rhodopseudomonas sphaeroides and Thiocapsa roseopersicina chromatophores is sensitive, and photooxidase activity of Ectothiorhodospira shaposhnikovii and Chlorobium limicola f. thiosulfatophilum is resistant to o-phenanthroline. O₂ uptake by illuminated chromatophores of R. rubrum and C. limicola is stimulated upon the increase of pH of incubation mixture from 5 to 9. Photooxidase activity is also manifested in the intact bacterial cells and not merely in the isolated chromatophores. O₂ uptake by the illuminated R. rubrum cells treated with CN^- is stimulated by 2-heptyl-4-hydroxyquinoline-N-oxide and a protonophorous uncoupler. The interaction of the photosynthetic and respiratory systems of the electron transfer in the bacterial cells and the probable causes of the strong anaerobic way of life of the green sulfur bacteria are discussed.HQNO 2-heptyl-4-hydroxyquinoline-N-oxide - TMPD N,N,-N,N-tetramethyl-p-phenylenediamine     

ATP is required for K+ active transport in the archaebacterium Haloferax volcanii

The Archaebacterium Haloferax volcanii concentrates K⁺ up to 3.6 M. This creates a very large K⁺ ion gradient of between 500- to 1,000-fold across the cell membrane. H. volcanii cells can be partially depleted of their internal K⁺ but the residual K⁺ concentration cannot be lowered below 1.5 M. In these conditions, the cells retain the ability to take up potassium from the medium and to restore a high internal K⁺ concentration (3 to 3.2 M) via an energy dependent, active transport mechanism with a K _m of between 1 to 2 mM. The driving force for K⁺ transport has been explored. Internal K⁺ concentration is not in equilibrium with m suggesting that K⁺ transport cannot be accounted for by a passive uniport process. A requirement for ATP has been found. Indeed, the depletion of the ATP pool by arsenate or the inhibition of ATP synthesis by N,N-dicyclohexylcarbodiimide inhibits by 100% K⁺ transport even though membrane potential m is maintained under these conditions. By contrast, the necessity of a m for K⁺ accumulation has not yet been clearly demonstrated. K⁺ transport in H. volcanii can be compared with K⁺ transport via the Trk system in Escherichia coli.Abbreviations CCCP Carbonylcyanide m-chlorophenyl-hydrazone - DCCD N,N-dicyclohexylcarbodiimide - MES 2-[N-morpholino] ethane sulfonic acid - MOPS 3-[N-morpholino] propane sulfonic acid - TRIS Tris (hydroxymethyl) aminomethane - TPP tetraphenyl phosphonium     

A novel substrate for yeast alcohol dehydrogenase – p-nitroso-N,N-dimethylaniline

Yeast alcohol dehydrogenase (EC 1.1.1.1) catalyzes the novel reduction of p-nitro-so-N,N-dimethylaniline with NADH as a cofactor. Apparent kinetic constants for this enzymatic reaction are: V ₂=2.1 s^–1, K _Q=456 M, K _iQ=119 M, and K _P=1.47 mM, at pH 8.9, 25 °C. This reaction is especially useful for the quantitative determination of NAD⁺ and NADH by enzymatic cycling.     

A thioredoxin-activated fructose-1,6-bisphosphatase from the cyanobacterium Synechococcus 6301

Fructose-1,6-bisphosphatase was isolated from the cyanobacterium Synechococcus 6301 by acid precipitation, ammonium-sulfate fractionation, and Sephadex gel chromatography. The purified enzyme needed thiols and MgCl₂ for activity. The following K_m-values were obtained: a) for fructose-1,6-bisphosphate: 1.7 mM; b) for MgCl₂: 12.5 mM; c) for dithiocrythritol: 0,56 mM; d) for glutathione: 14 mM; e) for mercaptoethanol: 22 mM; f) for cysteine: 50 mM. Thioredoxin B isolated from this organism will activate this fructose-1,6-bisphosphatase. The K_m of thioredoxin B for this fructose-1,6-bisphosphatase was determined to be 1.7 M, endicotiy that thioredoxin might activate the fructose-1,6-bisphosphatase in Synechococcus in vivo.     

Sulfate assimilation in Rhodopseudomonas globiformis

Rhodopseudomonas globiformis is able to grow on sulfate as sole source of sulfur, but only at concentrations below 1 mM. Good growth was observed with thiosulfate, cysteine or methionine as sulfur sources. Tetrathionate supported slow growth. Sulfide and sulfite were growth inhibitory. Growth inhibition by higher sulfate concentrations was overcome by the addition of O-acetylserine, which is known as derepressor of sulfate-assimilating enzymes, and by reduced glutathione. All enzymes of the sulfate assimilation pathway. ATP-sulfurylase, adenylylphosphate-sulfotransferase, thiosulfonate reductase and O-acetylserine sulfhydrylase are present in R. globiformis. Sulfate was taken up by the cells and the sulfur incorporated into the amino acids cysteine, methionine and homocysteine. It is concluded, that the failure of R. globiformis to grow on higher concentrations of sulfate is caused by disregulation of the sulfate assimilation pathway. Some preliminary evidence for this view is given in comparing the activities of some of the involved enzymes after growth on different sulfur sources and by examining the effect of O-acetylserine on these activities.Abbreviations DTE dl-dithioerythritol - APS adenosine 5-phosphosulfate, adenylyl sulfate - PAPS 3-phosphoadenosine 5-phosphosulfate, 3-phosphoadenylylsulfate     

Morphologie und Wirtskreis eines neu isolierten Rhodopseudomonas palustris-Phagen

Zusammenfassung Aus Teichwasser in der Nähe Freiburgs wurde ein Bacteriophage angereichert, der Rhodopseudomonas palustris, Stamm 1 e 5 befällt. Dieser, als Rp 1 bezeichnete Phage kann in anaeroben Lichtkulturen von Rps. palustris bis zu einem Titer von 10⁹ vermehrt werden. Der Infektionscyclus findet auch in aerober Dunkelkultur statt. Von 17 untersuchten Rps. palustris-Stämmen wird nur der Stamm 1 e 5 befallen und bei ihm die Entwicklung von Plaques beobachtet. Das Capsid des Phagen ist icosaedrisch. Die Capsomeren erscheinen pentagonal. Das Capsid hat einen Durchmesser von 380–390 . Die Festheftung des Phagen an der Oberfläche der Wirtszelle oder an den Thylakoiden erfolgt mit einer röhrenförmigen Struktur, die 200 lang und 55–60 dick ist.

---

Morphology and host range of a new isolated Rhodopseudomonas palustris-phage

Summary A Phage active against Rhodopseudomonas palustris was isolated from freshwater ponds near Freiburg. The Phage is called Rp 1. Rp 1 could be propagated to titres of 10⁹ plaque-forming units/ml in anaerobic light cultures. It is also synthesized in aerobic dark cultures of Rps. palustris strain 1 e 5. The host range of this phage is very narrow. Only one of seventeen strains of Rps. palustris is able to propagate the phage. The other tested Athiorhodaceae do not give rise to plaque development. The Rp 1 virus consists of an icosahedral head (380–390 in diameter) and a tail like structure. After degradation of the capsid pentagonal capsomeres become visible. The phages are attached by a hollow tube (length 200 , diameter 55–60 ) to the host cell. In negative stained preparations of phages many Rp 1 are seen attached to the thylakoid of the bacteria.

     

Purification and characterization of aspartate aminotransferase from developing embryos of the camel tick Hyalomma dromedarii

Aspartate transaminase (AST) activity in the camel tick Hyalomma dromedarii was followed throughout embryogenesis. During purification of AST to homogeneity, ion exchange chromatography lead to four separate forms (termed I, II, III and IV). AST II with the highest specific activity was pure after chromatography on Sephacryl S-300. The molecular mass of AST II was 52KDa for the native enzyme, composed of one subunit of 50KDa. AST II had a Km value of 0.67mM for -ketoglutarate and 15.1mM for aspartate. AST II had a pH optimum of 7.5 with heat stability up to 50°C for 15min. The enzyme was activated by MnCl₂, and inhibited by CaCl₂, MgCl₂, NiCl₂, and ZnCl₂.