The capsule and slime polysaccharides of the wild type and a phage resistant mutant ofRhodopseudomonas capsulata St. Louis

A rhamnose, galactose and pyruvic acid containing polysaccharide (capsule) together with the peptidoglycan was isolated fromRhodopseudomonas capsulata St. Louis as the insoluble sediment after sodium dodecyl sulfate extraction of cell envelope fractions. Treatment with pronase E separated the soluble polysaccharide from the insoluble peptidoglycan. After lysozyme-digestion, both the capsule polysaccharide and peptidoglycan were soluble.The capsule was also accumulated in the combined interphase/phenol-phase of hot phenol-water extracts of whole cells. Again, the capsule and peptidoglycan were sedimented together as long as no pronase E-treatment was performed. With the phage-resistant mutant (R. capsulata St. Louis RC1^-), no capsule polysaccharide was obtained in the combined interphase/phenol phase.An acidic polysaccharide (slime) different from the capsule in composition and serology was obtained by Cetavlon fractionation of hot phenol/water extracts of cells of both the wild-type and the mutant cells. It was shown to consist mainly of rhamnose, glucosamine and galacturonic acid.The use of O/K-antisera and of capsule polysaccharideantisera allowed a separate visualization of the capsule and slime layers.This paper is dedicated to Professor Hans G. Schoegel on the occasion of his 60th birthday     

Different polysaccharides in the external layers (capsule and slime) of the cell envelope of Rhodopseudomonas capsulata Sp11

Two different acidic polysaccharides (I and II) were detected in the external cell envelope layers (slime and capsule) of Rhodopseudomonas capsulata Sp11. Polysaccharide I contains rhamnose, fucose, glucosamine and an unknown acidic sugar, it represents the slime material of the strain. Polysaccharide II contains rhamnose, galactose, 3-amino-3,6-dideoxygalactose, an unknown amino sugar and galacturonic acid, it represents very likely the capsule of R. capsulata Sp11. Polysaccharide I has a serological specificity different from that of polysaccharide II as shown by immunoprecipitation using antisera against living cells. Polysaccharide II, but not polysaccharide I, reacts in antiserum against heat-treated cells (100 degrees C, 2.5 h). Whole cells are agglutinated in the antisera against living but not in those against heat-treated cells.     

DNA-DNA hybridization of Rhodopseudomonas capsulata,Rhodopseudomonas sphaeroides and Rhodopseudomonas sulfidophila strains

The genetic relatedness of 21 Rhodopseudomonas strains has been studied by means of DNA-DNA hybridization. All strains included in the study belonged to the subgroup of the genus Rhodopseudomonas which is characterized by a short-rod to coccus morphology, a vesicular intracytoplasmic membrane system and carotenoids of the spheroidene group. Mol percentages guanine + cytosine ranged from 64 to 73, most strains having values between 68 and 72. With few exceptions, the hybridization data obtained were in agreement with the subdivision in three (or possibly four) species on the basis of classical taxonomy. Strain SCJ, formerly considered to be a somewhat atypical R. capsulata strain, is most probably a R. sphaeroides strain and two out of seven strains that were received as R. sulfidophila did not fit in this species on the basis of the hybridization data. The results also showed that two undesignated strains that were previously thought to be related to R. capsulata (Hansen et al. 1975) cannot be assigned to this species and may be representatives of another species. The seven strains that required approximately 2.5% NaCl in the medium and that had been designated R. sulfidophila were found to synthesize far higher levels of bacteriochlorophyll during fully aerobic growth in the dark than the purple bacteria studied thus far.Abbreviations GC guanosine + cytosine - SSC standard saline citrate buffer     

Turnover of cell surface-bound capsular polysaccharide in Staphylococcus aureus

The capsular polysaccharide (CPS) of Staphylococcus aureus strain Smith was labelled by growth of bacteria in the presence of radioactive N-acetylglucosamine and was separated from labelled cell wall components by affinity chromatography on wheat germ agglutinin following dissolution of the cells by lysostaphin. The products were partially characterised chemically and immunochemically. Similar labelled components were found in the culture fluid during growth. In a pulse-chase experiment, cell-bound CPS was released continuously into the culture fluid at the same rate as cell wall turnover and there was no evidence of direct excretion of CPS.     

The siaA gene involved in capsule polysaccharide biosynthesis of Neisseria meningitidis B codes for N-acylglucosamine-6-phosphate 2-epimerase activity

The capsule polysaccharide of Neisseria meningitidis serogroup B is composed of a homopolymer of alpha-2-->8 linked N-acetyl-neuraminic acid (sialic acid). The enzymes required for sialic acid biosynthesis and polymerization are encoded in region A of the capsule gene complex. We here describe the enzymatic activity of the siaA gene product as determined by biochemical analysis. siaA was overexpressed in Escherichia coli and the SiaA protein was purified to homogeneity. Enzymatic assays revealed that SiaA did not accept N-acetyl-glucosamine as substrate, but only N-acetyl-glucosamine-6-phosphate (EC 5.1.3.9). SiaA catalyzes the isomerization of N-acetyl-glucosamine-6-phosphate to form N-acetyl-mannosamine-6-phosphate. This reaction represents the first step in capsule biosynthesis of N. meningitidis B.     

Diazotrophic growth of Rhodopseudomonas acidophila and Rhodopseudomonas capsulata under microaerobic conditions in the dark

Diazotrophy of Rhodopseudomonas acidophila and Rhodopseudomonas capsulata was not obligatorily linked to photosynthesis. In the dark R. acidophila grew with dinitrogen as sole nitrogen source at a dissolved oxygen tension of 15 Torr (= 2.0 kPa); the doubling time was 8 h. Acetylene reduction by whole cells was more sensitive to oxygen in the light than in the dark. 16.5 mg N₂ were fixed per g lactic acid consumed. R. capsulata synthesized nitrogenase and fixed dinitrogen in the dark at a dissolved oxygen tension of less than one Torr (= 0.13 kPa). The doubling time of this bacterium was 16 h and 10.5 mg N₂ were fixed per g lactic acid consumed.Abbreviation kPa kilopascal     

Composition,secretion kinetics and radioactive labelling of the extracellular slime polysaccharide secreted during spherulation ofPhysarum polycephalum

The myxomycetePhysarum polycephalum synthesizes copious amounts of slime when differentiating into the hard walled resting stage. The chemical composition of slime obtained after introduction of spherulation in a nutrient and a non-nutrient salt-medium has been analysed and compared. The composition of slime is almost identical after the two different induction methods. This slime could be labelled with radioactived-[U-¹⁴C]glucose,³²PO₄ ^3–,³⁵SO₄ ^2– and⁷⁵SeO₄ ^2–. The kinetics of slime secretion after both induction methods has been followed using different criteria. The sulfate analog⁷⁵SeO₄ ^2– seems to be incorporated into the slime, partially replacing sulfate groups of the sulfated polysaccharide. Furthermore,d-[U-¹⁴C]glucose was used to labe the spherule walls. Determination of an alkali resistent polysaccharide component serves as a new method to follow wall formation.     

The activity of two forms of nitrogenase from Rhodopseudomonas capsulata in the presence of different electron donors

Abstract The active form of Rhodopseudomonas capsulata nitrogenase is active in vitro when dithionite or ferredoxins from this bacterium are used as electron donors. The presence of the activating nitrogenase enzyme and Mn²⁺ ions is needed for functioning of the inactive form of Rh. capsulata nitrogenase in vitro with the use of dithionite as an electron donor. The use of Rh. capsulata ferredoxins as electron donors in vitro makes the inactive form of nitrogenase fully active as is the case in vivo.     

Golgi apparatus and slime secretion in plants: the early implications and recent models of membrane traffic

Summary The function of the Golgi apparatus in the secretion of plant slimes is reviewed. It is shown how the research on slime secretion has increased the knowledge on the structure and dynamics of dictyosomes. Current models on intradictyosomal membrane traffic-anterograde progression of complete cisternae or anterograde movement of lateral vesicles with stationary cisternae-are discussed in the light of old and new results on slime secreting plant cells.Dedicated to Hilton H. Mollenhauer on the occasion of his retirement     

The regulation of ferredoxin-dependent nitrogenase activity in Rhodospirillum rubrum and Rhodopseudomonas capsulata

Abstract The regulatory properties of Rhodospirillum rubrum nitrogenase reduced by either the endogenous electron donor (ferredoxin) or an artificial donor (dithionite) were examined. The nitrogenase obtained from glutamate-grown cells required activating enzyme for maximum activity with either reductant. The activating enzyme requirement of ferredoxin-dependent nitrogenase activity implies a physiological significance of the activating enzyme in R. rubrum. Rhodopseudomonas capsulata nitrogenase also required activating enzyme when dithionite was the reductant, but there appeared to be no activating enzyme requirement with ferredoxin as the reductant. Because the catalytic activity of the enzyme was very low under these conditions, the physiological significance of activating enzyme in this organism remains in question.     

Conservation and variation of ribosomal proteins in several species of the cellular slime molds Dictyostelium and Polysphondylium

Genus- and species-specific composition of ribosomal proteins was investigated in four species of the genus Dictyostelium (D. discoideum, D. purpureum, D. murcoroides and D. giganteum) and two species of the genus Polysphondylium (P. pallidum and P. violaceum). Ribosomal proteins were resolved by a high-resolution, two-dimensional gel method. In general, the numbers and distributions for the majority of ribosomal proteins were similar within the species of each genus, although some differences were detected. More differences were observed between Dictyostelium and Polysphondylium than among the individual species within each genus. Stage-specific ribosomal proteins previously demonstrated in D. discoideum were found to be developmentally regulated in other Dictyostelium species, and in both Polysphondylium species. The study shows that ribosomal proteins may be a potentially useful new biochemical parameter for the molecular taxonomy of the cellular slime molds.     

Urea: An intermediate of aerobic and anaerobic purine degradation in Rhodopseudomonas capsulata

Abstract A mutant strain ( pur ^-) defective in utilization of purines was isolated from Rhodopseudomonas capsulata . In the mutant, the loss of purine utilization correlated with urease deficiency. In contrast to the wild-type strain, the mutant catalyzed release of urea from purines. The nitrogen of the purine ring was completely liberated as urea indicating that the latter compound is an intermediate of the purine degradation pathway in Rps. capsulata . The degradation pattern was identical under aerobic and anaerobic conditions.     

The effect of dibromothymoquinone on respiratory and photosynthetic electron transport in Rhodopseudomonas capsulata chromatophores

Dibromothymoquinone has been shown to inhibit light-induced cytochrome b reduction, and oxidation of succinate and NADH by chromatophores of Rhodopseudomonas capsulata. The half-inhibitory concentration of light-induced reactions and NADH oxidation is 2.5 M, but of succinate oxidation is 16 M. Hexane extraction inhibited oxidation of NADH and succinate equally. The results are interpreted to suggest that ubiquinone is concerned in all three processes described, but that the pools associated with NADH and succinate oxidation are not equally accessible to dibromothymoquinone.Abbreviations DBMIB Dibromothymoquinone - NADH Reduced nicotinamide adenine dinucleotide - Bchl Bacteriochlorophyll     

UV-B对两种藻光合色素和多糖含量的影响

本文研究了微绿球藻(Nanochloropsis sp.)和海洋原甲藻(Prorocentrum micans)在不同辐射强度的UV-B照射下的光合色素和多糖含量的变化,结果表明微绿球藻比原甲藻有更强的抗紫外辐射能力.它的叶绿素a含量在UV照射下保持相对稳定,而原甲藻的叶绿素a含量明显下降.同时发现微绿球藻中的类胡萝卜素含量有十分显著的上升,由于类胡萝卜素具有保护功能,因此它很可能保护了叶绿素a免遭破坏,从而在微绿球藻的抗紫外辐射中起到重要作用.另外,紫外处理也促进了微绿球藻中多糖含量的升高,这也有利于提高它的抗UV能力,多糖可能作为一种保护机制,对保护藻类防止UV伤害方面有一定功能.原甲藻则因为这些机能较弱,对UV的抗性较低.     

Achene morphology and slime structure in some taxa of Artemisia L. and Neopallasia L. (Asteraceae)

We have examined slime cell distribution on the surface of the achenes of some Artemisia and Neopallasia taxa, as well as slime composition, envelope formation during the hydration, and slime relation to different morphological features and environmental factors. The results of the studies show a characteristic pattern of slime cells distribution, which could differ between taxa. The slime in the taxa studied belongs to the cellulose type and consists of two components i.e., pectins and cellulose. Although all fruits contain slime cells, not all of them show the slime envelope formation. Plants occurring in dry habitats (such as A. barrelieri) or annual species (such as A. annua) are characterised by a large amount of slime and a fast process of slime envelope formation. Slime production has not been observed in some polyploid populations (A. campestris and A. campestris ssp. sericea) and in two species occurring in relatively fertile habitats (A. verlotiorum, A. vulgaris). A reason for this may be either the immaturity of polyploid fruits leading to the production of a scarce, not detectable slime amount or, alternatively, the occurrence of not functional slime cells. Slime facilitates and stimulates the germination, as well as the adherence of the fruits to the ground or to animals (for dispersal). The slime could play important role in the distribution and colonisation of new habitats in many Artemisia taxa.     

Reconstitution of b-type cytochrome oxidase from Rhodopseudomonas capsulata in liposomes and turnover studies of proton translocation

Purified b-type cytochrome oxidase from Rhodopseudomonas capsulata was incorporated into phospholipid vesicles to measure proton extrusion with pulses of ferrocytochrome c for one oxidase turnover. In accordance with the pH shift of its midpoint potential, the purified oxidase showed a proton extrusion of 0.24 $\text{H}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}$ with uptake of 1 $\text{H}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}$ from the liposomes for the reduction of oxygen to water. This proton translocation could only be observed in the presence of valinomycin +K⁺ and was not inhibited by DCCD. Oxidase preparations from the first purification step, which contain other protein compounds especially a membrane-bound cytochrome c but not the ubiquinol-cytochrome c₂-oxidoreductase showed a pumping activity of 0.9 $\text{H}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}$, which was inhibited by DCCD for nearly 75%. Inhibition of the electron transfer was not observed, which could be explained by a ‘molecular slipping’ of proton extrusion and electron transfer. Proton extrusion from two oxidase-turnovers was only 80% of that from one turnover. The proton pumping of the b-type oxidase strongly depended on the enzyme/phospholipid ratio.     

Structural characterization of Streptococcus pneumoniae serotype 9A capsule polysaccharide reveals role of glycosyl 6-O-acetyltransferase wcjE in serotype 9V capsule biosynthesis and immunogenicity

The putative capsule O-acetyltransferase gene wcjE is highly conserved across various Streptococcus pneumoniae serotypes, but the role of the gene in capsule biosynthesis and bacterial fitness remains largely unclear. Isolates expressing pneumococcal serotype 9A arise from precursors expressing wcjE-associated serotype 9V through loss-of-function mutation to wcjE. To define the biosynthetic role of 9V wcjE, we characterized the structure and serological properties of serotype 9V and 9A capsule polysaccharide (PS). NMR data revealed that both 9V and 9A PS are composed of an identical pentasaccharide repeat unit, as reported previously. However, in sharp contrast to previous studies on 9A PS being devoid of any O-acetylation, we identified O-acetylation of α-glucuronic acid and α-glucose in 9A PS. In addition, 9V PS also contained -CH(2) O-acetylation of β-N-acetylmannosamine, a modification that disappeared following in vitro recombinatorial deletion of wcjE. We also show that serotyping sera and monoclonal antibodies specific for 9V and 9A bound capsule PS in an O-acetate-dependent manner. Furthermore, IgG and to a lesser extent IgM from human donors immunized with serotype 9V PS displayed stronger binding to 9V compared with 9A PS. We conclude that serotype 9V wcjE mediates 6-O-acetylation of β-N-acetylmannosamine. This PS modification can be selectively targeted by antibodies in immunized individuals, identifying a potential selective advantage for wcjE inactivation and serotype 9A emergence.