Die Variation bei den Statoblasten von Pectinatella magnifica

Ohne Zusammenfassung     

Airborne dispersal of antarctic terrestrial algae and cyanobacteria

The dispersal of algae and cyanobacteria at three Antarctic fellfield sites was investigated using microscopic and culture analysis of samples from active and passive air samplers Intersite variation in the mean number of large algal propagules (>5 μm diameter) sampled was dependent on the niche space available for algal growth and the degree to which soil was exposed to desiccating influences, these factors could be related to the degree of maturity of the sue The numbers of large algal propagules were lowest at sites from which permanent snow cover had recently disappeared and highest at sites with developed soil circles but poorly developed moss and lichen flora Mature sites with diverse and developed moss and lichen flora produced intermediate numbers of algal propagules Propagules of multicellular algae, cyanobacteria and large-celled unicellular algae were found in the air at the end of the growing season of the respective algal groups as the soil surface dried This was the case for Prasiola crispa, Pmnularia borealis , snow algae and filamentous chlorophytes and cyanobacteria Dispersal of unicellular chlorophytes was greatest during the summer period and at sites with developed secondary flora, but also occurred at other sites and in association with small thaw events during winter Cultures were obtained from samples collected whilst an air mass that had originated in South America, deposited material on Signy Island This suggests that algal propagules have the ability to survive long-distance transport and potentially provide mocula for colonization of Antarctica as regional warming continues to expose fresh habitats     

Extracellular fibril production by freshwater algae and cyanobacteria

In order to study the ability of freshwater algae and cyanobacteria to form extracellular fibrils, a screening test using ruthenium red (RR) staining was carried out on 28 species. Five of these were examined for growth and production of fibrillar material in culture media of different phosphate (P;) contents. RR-staining and uronic acid determinations at various stages of algal growth were complemented by electron microscopy of the cells and of fibrillar material released into the medium. The lower P_i concentrations enhanced growth of Micrasterias radiata, Eremosphaera sp., and Microcystis aeruginosa, and had little or no effect on growth of a Xanthidium sp. and Scenedesmus quadricauda. Extracellular uronic acid production, which was higher in low P_i medium in M. radiata, M. aeruginosa, and Xanthidium sp., could reach levels of 50 mg/liter or more. Algae with high proportions of RR-positive cells (M. radiata, Eremosphaera sp., Xanthidium sp., and M. aeruginosa) produced high levels of slime-like material and distinct fibrils that were often seen attached to the cell surface and only slowly released into the medium. No such material was found in cultures (or supernatants) of Sc. quadricauda, which also produced relatively low amounts of polyuronic acids. Specific types of filaments, often forming fascicles with rectangular arrays of globular particles were observed by negative staining electron microscopy of some algal cultures. RR-positive material was also observed in the cytoplasm and on the cell walls and surfaces of M. radiata and M. aeruginosa.Offprint requests to: D. J. Kushner.     

Accessory polypeptides in phycobilisomes of red algae and cyanobacteria

Phycobilisomes of red algae and cyanobacteria contain small amounts of nonpigmented polypeptides in addition to the major constituent biliprotein pigments. The localization of these polypeptides is analyzed by gel electrophoresis of phycobilisome fragments obtained by selective dissociation and subsequent separation. Five groups of biliprotein aggregates are determined, belonging to the 6, 11, 16, 18 and 23 S categories. Accessory nonpigmented high molecular weight proteins (80,000 MW) are exclusively bound to phycobilisome core fractions and thylakoids, thus apparently serving as links between the phycobilisomes and the photosynthetic units of the thylakoids. In contrast, smaller nonpigmented accessory polypeptides of 20,000 to 60,000 MW are preferably found in the peripheral biliprotein stacks. They may either form a compatible link between the phycobilisome core and periphery or bind and co-polymerize with hexameric biliproteins in the peripheral stacks to enhance or effect binding of the aggregates. Furthermore, they may determine the arrangement and composition of the phycobilisomes during development and chromatic adaptation.Abbreviations PE phycoerythrin - PEC phycoerythrocyanin - PC phycocyanin - APC allophycocyanin     

Biodegradation of dyes by some green algae and cyanobacteria

The ability of Chlorella vulgaris, Lyngbya lagerlerimi, Nostoc lincki, Oscillatoria rubescens, Elkatothrix viridis and Volvox aureus to decolorize and remove methyl red, orange II, G-Red (FN-3G), basic cationic, and basic fuchsin was investigated. These algae showed different efficiency for colour removal; varied from 4 to 95% according to the algal species, its growth state and the dye molecular structure. Basic cationic and basic fuchsin were the most susceptible dyes for decolorisation and removal by all algae being tested, and up to 82% of methyl red was also removed by N. lincki and O. rubescens. However, the algal activity to decolorize orange II and G-Red was markedly fluctuated and lower. C. vulgaris displayed activity to remove 43.7 and 59.12% while as V. aureus removed 5.02 and 3.25% of the added dyes respectively. The results also showed that treatment of either C. vulgaris or N. Linckia with G-Red or methyl red, respectively, induced the algal azo dye reductase enzyme by 72 and 71% at the same order.     

The low-potential cytochrome c of cyanobacteria and algae.

A water-soluble, low-potential cytochrome c-550 is found in some cyanobacteria and eukaryotic algae and has regions of sequence similarity to cytochrome c6. This cytochrome appears to be involved in a fermentation that sustains the organisms during prolonged periods of dark, anaerobic conditions.     

Tolerance of soil algae and cyanobacteria to drought stress

Tolerance to drought stress in soil crust microorganisms is essential for exploiting suitable organisms for restoring soil. In this study, the responses to drought stress of two drought‐tolerant species, a green alga and a cyanobacterium, were compared with those of two non‐tolerant green algae. In response to drought stress, induced by treatment with polyethylene glycol, the intracellular proline levels increased and were associated with increases in malondialdehye, pigment contents, and enzyme activities such as superoxide dismutase (SOD) and peroxidase (POD). Our results suggest that tolerance to drought stress could be indicated by the intracellular levels of proline, SOD, and carotenoids. This study provides insights into the drought physiology of the photosynthetic microorganisms and suggests that Leptolyngbya boryana and Chlorella vulgaris are suitable pioneer organisms for soil restoration.     

Responses of aquatic algae and cyanobacteria to solar UV-B

Continuous depletion of the stratospheric ozone layer has resulted in an increase in solar ultraviolet-B (UV-B; 280–315 nm) radiation reaching the Earth's surface. The consequences for aquatic phototrophic organisms of this small change in the solar spectrum are currently uncertain. UV radiation has been shown to adversely affect a number of photochemical and photobiological processes in a wide variety of aquatic organisms, such as cyanobacteria, phytoplankton and macroalgae. However, a number of photosynthetic organisms counteract the damaging effects of UV-B by synthesizing UV protective compounds such as mycosporine-like amino acids (MAAs) and the cyanobacterial sheath pigment, scytonemin. The aim of this contribution is to discuss the responses of algae and cyanobacteria to solar UV-B radiation and the role of photoprotective compounds in mitigating UV-B damage.     

Viability of lyophilized cyanobacteria (blue-green algae).

Lyophilizatin of 13 cyanobacterial cultures belonging to seven genera was attempted in a variety of suspending substances. All organisms survived lyophilization when suspended in lamb serum. Some of the organisms could be successfully lyophilized in horse serum, beef serum, fetal bovine serum, or human ascites fluid. With the exception of Nostoc muscorium, none of the organisms survived lyophilization in skim milk medium, egg albumin medium, or Jansen salts medium.     

Blue-green algae (cyanobacteria): prospects and perspectives

Summary Photosynthetic, prokaryotic blue-green algae (cyanobacteria) occur in a wide range of natural habitats of diverse ionic composition and as such, represent an important source of biological material for biosolar energy conversion programs using saline water. The gasvacuolate, filamentous Spirulina is grown in seminatural culture in Lake Texcoco, Mexico, as a major source of single-cell protein for animal nutrition. Pilot-scale trials in other areas of the world have also demonstrated the suitability of blue-green algae, including Spirulina, for growth under brackish conditions. The carbohydrate accumulation profiles of blue-green algae differ in isolates from freshwater, marine and hypersaline habitats, with a trend towards sucrose or trehalose accumulation in stenohaline freshwater strains grown in media containing NaCl, while euryhaline and marine forms frequently accumulate glucosylglycerol. Many halotolerant isolates from hypersaline habitats accumulate glycinebetaine in response to osmotic stress. This knowledge may provide scope for future improvement in the N₂ fixation rates of blue-green algae in saline media, using betaine-accumulating N₂-fixing strains in preference to other, saltsensitive isolates.     

Microscopic green algae and cyanobacteria in high-frequency intermittent light

The effects of fluctuations in the irradiance onScenedesmus quadricauda, Chlorella vulgaris andSynechococcus elongatus were studied in dilute cultures using arrays of red light emitting diodes. The growth rate and the rate of photoinhibition were compared using intermittent and equivalent continuous light regimes in small-size (30 ml) bioreactors. The CO₂ dependent photosynthetic oxygen evolution rates in the intermittent and continuous light regimes were compared for different light/dark ratios and different mean irradiances. The kinetics of the electron transfer reactions were investigated using a double-modulation fluorometer. The rates of photosynthetic oxygen evolution normalized to equal mean irradiance were lower or equal in the intermittent light compared to the maximum rate found in the equivalent optimal continuous light regime. In contrast, the growth rates in the intermittent light can be higher than the growth rate in the equivalent continuous light. Photoinhibition is presented as an example of a physiological process affecting the growth rate that occurs at different rates in the intermittent and equivalent continuous lights. The difference in the dynamics of the redox state of the plastoquinone pool is proposed to be responsible for the low photoinhibition rates observed in the intermittent light.     

Fluorescence characteristics of cyanobacteria (blue-green algae)

The fluorescence characteristics of the cyanobacteria Synechocystisaquatilis Sauv., Microcystis firma (Breb. et Lenorm.) Schmidleand Synechococcus leopoliensis (Racib.) Kom. and the green algaScenedesmus quadricauda (Turp.) Breb. were examined. In thethree cyanobacteria, phycocyanin is the main accessory pigment.Phycoerythrin is not present in our investigated strains ofcyanobacteria. The highest excitation of the chlorophyll a (Chla) fluorescence of cyanobacteria resulted from light with wavelengthsof 620–630 nm. A definite ‘Kautsky’ effectis also evident at this wavelength. However, excitation withblue light (420–520 nm) produced only very slight fluorescence.The Kautsky effect is not evident at these wavelengths, evenat high photon flux densities. For Scenedesmus, fluorescencecharacteristics typical of green algae were found. The fluorescenceexcitation of cyanobacteria at 620 nm corresponds to a photosynthesispeak in the action spectrum measured in terms of O₂ production.The results underline the necessity of fluorescence measurementsat several wavelengths whenever mixed populations are involved.Such measurements also present possibilities for more accurateestimation of biomass and potential photosynthetic productionin mixed populations.     

The respiratory chain of blue-green algae (cyanobacteria)

Electron transport components on the way from reduced substrates to the terminal respiratory oxidase(s) are discussed in relation to analogous and/or homologous enzymes and electron carriers in the generally much better known bacteria, mitochondria and chloroplasts. The kinetic behaviour of the components, their localization within the cell and their evolutionary position are given special attention. Pertinent results from molecular genetics are also mentioned. The unprecedented role of cyanobacteria for our biosphere and our whole planet earth appears to deserve a more extended introductory chapter.     

Coevolution of metal availability and nitrogen assimilation in cyanobacteria and algae

Marine primary producers adapted over eons to the changing chemistry of the oceans. Because a number of metalloenzymes are necessary for N assimilation, changes in the availability of transition metals posed a particular challenge to the supply of this critical nutrient that regulates marine biomass and productivity. Integrating recently developed geochemical, biochemical, and genetic evidence, we infer that the use of metals in N assimilation – particularly Fe and Mo – can be understood in terms of the history of metal availability through time. Anoxic, Fe-rich Archean oceans were conducive to the evolution of Fe-using enzymes that assimilate abiogenic     and     The N demands of an expanding biosphere were satisfied by the evolution of biological N₂ fixation, possibly utilizing only Fe. Trace O₂ in late Archean environments, and the eventual 'Great Oxidation Event' c . 2.3 Ga, mobilized metals such as Mo, enabling the evolution of Mo (or V)-based N₂ fixation and the Mo-dependent enzymes for     assimilation and denitrification by prokaryotes. However, the subsequent onset of deep-sea euxinia, an increasingly-accepted idea, may have kept ocean Mo inventories low and depressed Fe, limiting the rate of N₂ fixation and the supply of fixed N. Eukaryotic ecosystems may have been particularly disadvantaged by N scarcity and the high Mo requirement of eukaryotic     assimilation. Thorough ocean oxygenation in the Neoproterozoic led to Mo-rich oceans, possibly contributing to the proliferation of eukaryotes and thus the Cambrian explosion of metazoan life. These ideas can be tested by more intensive study of the metal requirements in N assimilation and the biological strategies for metal uptake, regulation, and storage.     

Nitrifying bacterial growth inhibition in the presence of algae and cyanobacteria

Nitrifying bacteria, cyanobacteria, and algae are important microorganisms in open pond wastewater treatment systems. Nitrification involving the sequential oxidation of ammonia to nitrite and nitrate, mainly due to autotrophic nitrifying bacteria, is essential to biological nitrogen removal in wastewater and global nitrogen cycling. A continuous flow autotrophic bioreactor was initially designed for nitrifying bacterial growth only. In the presence of cyanobacteria and algae, we monitored both the microbial activity by measuring specific oxygen production rate (SOPR) for microalgae and cyanobacteria and specific oxygen uptake rate (SOUR) for nitrifying bacteria. The growth of cyanobacteria and algae inhibited the maximum nitrification rate by a factor of 4 although the ammonium nitrogen fed to the reactor was almost completely removed. Terminal restriction fragment length polymorphism (T‐RFLP) analysis indicated that the community structures of nitrifying bacteria remained unchanged, containing the dominant Nitrosospira, Nitrospira, and Nitrobacter species. PCR amplification coupled with cloning and sequencing analysis resulted in identifying Chlorella emersonii and an uncultured cyanobacterium as the dominant species in the autotrophic bioreactor. Notwithstanding their fast growth rate and their toxicity to nitrifiers, microalgae and cyanobacteria were more easily lost in effluent than nitrifying bacteria because of their poor settling characteristics. The microorganisms were able to grow together in the bioreactor with constant individual biomass fractions because of the uncoupled solids retention times for algae/cyanobacteria and nitrifiers. The results indicate that compared to conventional wastewater treatment systems, longer solids retention times (e.g., by a factor of 4) should be considered in phototrophic bioreactors for complete nitrification and nitrogen removal. Biotechnol. Bioeng. 2010;107: 1004–1011. © 2010 Wiley Periodicals, Inc.     

Structure and biosynthesis of toxins from blue-green algae (cyanobacteria)

Microcystis andNodularia species produce cyclic hepta- and pentapeptides, microcystins and nodularin, respectively, both containing the same unusual C₂₀ amino acid, abbreviated Adda. Biosynthesis of nodularin fromNodularia and especially of Adda employs a pathway similar to that employed byMicrocystis for producting microcystins. Nearly 30 new microcystins have been isolated in our laboratory from cyanobacteria species and their structures assigned, largely employing tandem FAB mass spectrometry (FABMS/CID/MS). Acyclic peptides, some of them presumed precursors of nodularin and microcystins, have now been isolated and characterized. The numerous analogs identified or synthesized allow the identification of important parameters in a structure-activity relationship study.     

Distribution of sym-homosperimidine in eubacteria, cyanobacteria, algae and ferns

Abstract Polyamines were analyzed in 12 of N₂-fixing aerobic eubacteria and other eubacteria, cyanobacteria, algae and ferns. sym -Homospermidine (homospermidine) was found to be widely distributed as a major polyamine in various N₂-fixing eubacteria which belong to Azospirillum, Agromonas, Beijerinckia, Bradyrhizobium, Rhizobium and Xathnbacter . 3 species of Azotobater contained spermidine but not homospermidine, though they are N₂-fixing eubactera. Homospermidine is also distributed in some eubacteria, i.e., the photosynthetic Rhodopseudomanas rutila and the sulfur-oxidizing Thiobacillus denitrificans , a cyanobacterium, Synechococcus sp., and in the cyanobacterium-symbiotic ferns, Azolla imbircatta and Azolla japonica .     

Oxygen-dependent proton efflux in cyanobacteria (blue-green algae).

The oxygen-dependent proton efflux (in the dark) of intact cells of Anabaena variabilis and four other cyanobacteria (blue-green algae) was investigated. In contrast to bacteria and isolated mitochondria, an H+/e ratio (= protons translocated per electron transported) of only 0.23 to 0.35 and a P/e ratio of 0.8 to 1.5 were observed, indicative of respiratory electron transport being localized essentially on the thylakoids, not on the cytoplasmic membrane. Oxygen-induced acidification of the medium was sensitive to cyanide and the uncoupler carbonyl cyanide m-chlorophenylhydrazone. Inhibitors such as 2,6-dinitrophenol and vanadate exhibited a significant decrease in the H+/e ratio. After the oxygen pulse, electron transport started immediately, but proton efflux lagged 40 to 60 s behind, a period also needed before maximum ATP pool levels were attained. We suggest that proton efflux in A. variabilis is due to a proton-translocating ATP hydrolase (ATP-consuming ATPase) rather than to respiratory electron transport located on the cytoplasmic membrane.