Absence of gas vesicle protein in a mutant of Anabaena flos-aquae

Filaments without gas vacuoles arose spontaneously in the gas-vacuolate alga Anabaena flos-aquae. The non-vacuolate mutant was enriched by repeated sedimentation and subsequently cloned by microsyringe transfer. No revertants have been observed. In the gas-vacuolate wild-type alga the gas vesicle protein was clearly distinguished by gel electrophoresis as one of the ten most abundant protein species present in whole cell extracts. Electrophoresis indicated that the mutant had lost the ability to synthesize the gas vesicle protein. A second mutant partially defective in production of gas vacuoles and gas vesicle protein has been isolated.Abbreviations gv gas vesicle protein - pb phycobilin - TCA trichloracetic acid     

The occurrence of gas-vacuolate bacteria in lakes

In order to assess the importance of gas vacuoles in planktonic bacteria we carried out a survey of 35 lakes of different types. At least 39 morphologically distinct species of gas-vacuolate bacteria were encountered. All of the freshwater lakes, and one of two seawater-flooded quarries, which became thermally stratified in summer, contained gas-vacuolate bacteria in their anaerobic hypolimnia; however, with one exception, none was found in isothermally mixed lakes. This pattern of distribution supports the idea that gas vacuoles are important in providing buoyancy, a function which is relevant only in non-turbulent aquatic systems.     

Vertical distribution of the soil microbiota along a successional gradient in a glacier forefield

Spatial patterns of microbial communities have been extensively surveyed in well‐developed soils, but few studies investigated the vertical distribution of micro‐organisms in newly developed soils after glacier retreat. We used 454‐pyrosequencing to assess whether bacterial and fungal community structures differed between stages of soil development (SSD) characterized by an increasing vegetation cover from barren (vegetation cover: 0%/age: 10 years), sparsely vegetated (13%/60 years), transient (60%/80 years) to vegetated (95%/110 years) and depths (surface, 5 and 20 cm) along the Damma glacier forefield (Switzerland). The SSD significantly influenced the bacterial and fungal communities. Based on indicator species analyses, metabolically versatile bacteria (e.g. Geobacter) and psychrophilic yeasts (e.g. Mrakia) characterized the barren soils. Vegetated soils with higher C, N and root biomass consisted of bacteria able to degrade complex organic compounds (e.g. Candidatus Solibacter), lignocellulolytic Ascomycota (e.g. Geoglossum) and ectomycorrhizal Basidiomycota (e.g. Laccaria). Soil depth only influenced bacterial and fungal communities in barren and sparsely vegetated soils. These changes were partly due to more silt and higher soil moisture in the surface. In both soil ages, the surface was characterized by OTUs affiliated to Phormidium and Sphingobacteriales. In lower depths, however, bacterial and fungal communities differed between SSD. Lower depths of sparsely vegetated soils consisted of OTUs affiliated to Acidobacteria and Geoglossum, whereas depths of barren soils were characterized by OTUs related to Gemmatimonadetes. Overall, plant establishment drives the soil microbiota along the successional gradient but does not influence the vertical distribution of microbiota in recently deglaciated soils.     

In vivo photoinactivation of ribulose bisphosphate carboxylase in the gas-vacuolate cyanobacteriumMicrocystis aeruginosa

Irradiation of buoyant, gas-vacuolate cells of the cyanobacteriumMicrocystis aeruginosa by 5·10⁴ Wm^–2 of blue light for 1 h caused a 5% loss of extractable ribulose bisphosphate carboxylase activity compared to dark and red-light controls. Ribulose bisphosphate carboxylase activity was unaffected by blue light in similar experiments conducted with cells containing collapsed gas vacuoles.Abbreviations RuBP Ribulose 1,5-bis-phosphate carboxylase     

The identification of gas vacuoles and their abundance in the hypolimnetic bacteria of Arco Lake,Minnesota

Bright refractile granules in bacterial cells are identified as gas vacuoles if they disappear on application of a few atmospheres pressure. This paper describes a simple method for observing individual cells under the light microscope before and after application of pressure and the use of this method in making a comprehensive survey of gas-vacuolate organisms in a sample. In water samples from the hypolimnion of a stratified lake (Arco Lake) in Northern Minnesota, gas vacuoles were found in nearly 30 different bacteria, representing possibly 60% or more of those present. The pressure sensitivity of gas vacuoles in these organisms is illustrated by micrograph pairs. Gas vacuoles, which are otherwise uncommon in bacteria, are evidently of great selective value in the hypolimnia of stratified lakes, perhaps by regulating cell buoyancy.     

Pelodictyon phaeoclathratiforme sp. nov., a new brown-colored member of the Chlorobiaceae forming net-like colonies

A new strain of the green sulfur bacteria was isolated from the monimolimnion of Buchensee (near Radolfzell, Lake Constance region, FRG). Single cells were rod-shaped, nonmotile and contained gas vacuoles. Typical net-like colonies were formed by ternary fission of the cells. As photosynthetic pigments bacteriochlorophylls a, e, isorenieratene and -isorenieratene were present. Sulfide, sulfur and thiosulfate were used as electron donors during anaerobic phototrophic growth. Besides carbon dioxide, acetate and propionate could serve as carbon sources under mixotrophic conditions in the light. Like all other members of the green sulfur bacteria, the new bacterium is strictly anaerobic and obligately phototrophic. The possession of gas vacuoles and the formation of net-like colonies and the guanine plus cytosine content of the DNA (47.9 mol% G+C) are typical characteristics of the genus Pelodictyon. Because of its photosynthetic pigments which differ from those of Pelodictyon clathratiforme, strain BU 1 represents a new species, P. Phaeoclathratiforme sp. nov.     

The properties and buoyancy-providing role of gas vacuoles in Trichodesmium Ehrenberg

All three species of the marine blue-green alga Trichodesmium collected in the Sargasso and Caribbean seas were found to possess gas vacuoles. The constituent gas vesicles were much stronger than those found in any freshwater blue-green alga, the mean critical collapse pressures being 12 bars in T. erythraeum, 34 bars in T. contortum and 37 bars in T. thiebautii. This great strength is obviously an adaptation to the hydrostatic pressures at the depths to which these organisms occur in the ocean. In each case the gas vesicles are far too strong to be collapsed by rising cell turgor pressure, though gas-vacuolation could be slowly regulated by the differential growth of gas vesicles and cells. Since the vesicles are of a similar shape and size to those in other species, the vesicle wall material must be stronger. The majority of Trichodesmium colonies collected were positively buoyant, and in all cases tested the buoyancy was dependent on the presence of gas vacuoles. The buoyancy is important in increasing the residence time of these slowly growing algae in the euphotic zone and it is responsible for the surface water-blooms which they form.     

Thermal stability and phytoplankton distribution

Thermal stability is the potential of water columns to mix, and has long been known to fundamentally influence the vertical and temporal distribution of phytoplankton. Essentially this is because it indirectly controls the amount of light available to phytoplankton.Under stable conditions of strong temperature gradients algal species (or assemblages of associated species) distribute vertically because they have sufficient time to exploit the attenuated light field at their preferred depths. This encourages a species diversity which, in the Southern Hemisphere, is especially exemplified by the extremely stable conditions under the permanent ice of Antarctic lakes.In other lakes stability commonly encourages growth of blue-green algae by permitting their positive buoyancy to place them in optimal light conditions, and by inhibiting the resuspension of competing non-buoyant species. Analogous patterns occur with motile species (Dinophyceae, Cryptophyceae, etc.), and with non-motile forms whose physiological adaptations allow growth to large sub-surface peaks at preferred depths. These sub-surface maxima can be upwelled to the water surface, in a manner controlled by thermal stability and vertical shear, and horizontally transported to give large variations in horizontal distribution.At all latitudes diel stability cycles in surface waters can affect physiological properties important for growth, and in some circumstances can dominate the phytoplankton dynamics and distribution.Such short-term stability events merge with longer-term (e.g. annual) events with no conceptual distinction. A modern way to integrate this continuity is by scaling using spectral analysis of cyclicity. This allows biological variables (algal biomass, numbers, production) to be stochastically related to indices of stability (e.g. Brunt-Väisälä frequency).     

Gliding motility of Peloploca spp., and their distribution in the sediment and water column of a eutrophic lake

Observations indicating gliding motility in the gas-vacuolate, filamentous organism Peloploca were made using microcapillary tubes. Tubes containing semi-solid agar, incubated in sediment cores gave good enrichments of Peloploca spp. The organisms, which had the form of helical bundles of filaments, were seen to corkscrew through the agar at up to 2–3 m s^-1.The vertical distribution of Peloploca spp. in the sediment and water column of a eutrophic lake was examined periodically during summer stratification. The organisms were confined to anoxic conditions in the sediment prior to stratification. With increasing anoxia in the hypolimnion, the population shifted upwards in the sediment, and towards the end of stratification, in the most reducing conditions, appeared in the lower hypolimnion. Anaerobically incubated sediment cores also showed the movement of the Peloploca population from sediment into the overlying water.It is suggested that the gliding motility and helical morphology of Peloploca bundles enable them to migrate through sediment in response to oxygen and Eh gradients, in addition to their use of gas vacuoles to adjust their position in the water column. The taxonomic implications of gliding motility in Peloploca spp. are discussed.     

Ecophysiological properties of photosynthetic bacteria from the Black Sea chemocline zone

In May 1998, during the fifty-first voyage on board the research vessel Professor Vodyanitskii, a comparative study was conducted of the species diversity of green and purple sulfur bacteria in the water column of the chemocline zone at deep-sea stations and on the bottom surface of the Black Sea shallow regions. At three deep-sea stations, the accumulation of photosynthetic bacteria in the chemocline zone at a depth of 85–115 m was revealed on the basis of the distribution of potential values of carbon dioxide light fixation. The location of the site of potential carbon dioxide light fixation suggests that the photosynthesis may be determined by the activity of the brown Chlorobium sp., earlier revealed at these depths. Enrichment cultures of brown sulfur bacteria were obtained from samples taken at the deep-sea stations. By morphology, these bacteria, assigned to Chlorobium sp., appear as nonmotile straight or slightly curved rods 0.3–0.5 × 0.7–1.2 µm in size; sometimes, they form short chains. Ultrathin sections show photosynthetic antenna-like structures, chlorosomes, typical of Chlorobiaceae. The cultures depended on the presence of NaCl (20 g/l) for growth, which corresponds to the mineralization of Black Sea water. The bacteria could grow photoautotrophically, utilizing sulfide, but the Black Sea strains grew much more slowly than the known species of brown sulfur bacteria isolated from saline or freshwater meromictic lakes. The best growth of the strains studied in this work occurred in media containing ethanol (0.5 g) or sodium acetate (1 g/l) and low amounts of sulfide (0.4 mM), which is consistent with the conditions of syntrophic growth with sulfidogens. The data obtained allow us to conclude that the cultures of brown sulfur bacteria are especially adapted to developing at large depths under conditions of electron donor deficiency owing to syntrophic development with sulfate reducers. The species composition of the photosynthetic bacteria developing in the bottom sediments of shallow stations differed substantially from that observed at deep-sea stations. Pure cultures of the green Chlorobium sp. BS 1C and BS 2C (chlorobactin as the carotenoid), purple sulfur bacteria Chromatium sp. BS 1Ch (containing spirilloxanthine series pigments), and Thiocapsa marina BS 2Tc (containing the carotenoid okenone) were obtained from samples of sediments at shallow-water stations. Brown sulfur bacteria were absent in the sediment samples obtained from the Black Sea shallow-water stations 1 and 2.__________Translated from Mikrobiologiya, Vol. 74, No. 2, 2005, pp. 239–247.Original Russian Text Copyright © 2005 by Gorlenko, Mikheev, Rusanov, Pimenov, Ivanov.     

Physiological effects of the presence and absence of gas vacuoles in the blue-green alga,Microcystis aeruginosa Kuetz. emend. Elenkin

Physiological evidence was obtained for a light shielding role for gas vacuoles inMicrocystis aeruginosa Kuetz. emend. Elenkin, by comparing photosynthetic oxygen evolution, growth behaviour and pigment composition of cells with intact or collapsed gas vacuoles. The oxygen evolution rates were strongly dependent on cell concentration, a maximum rate for cells with intact gas vacuoles occurring at about 1.4×10⁹ cells/ml and for cells with collapsed gas vacuoles at about 2.5×10⁹ cells/ml. By using light saturation curves for oxygen evolution, it was estimated that at low light intensities up to 30% of the photosynthetically useable light was shielded at a cell concentration of 6×10⁸ cells/ml. Collapsing the gas vacuoles twice daily did not alter the initial growth rate of the cultures, but enabled them to reach a higher final cell density. Collapsing of gas vacuoles during growth for about four generations resulted in a lower level of all acetone soluble pigments with a greater relative reduction in carotenoids than in chlorophyll a. Collapse of the gas vacuoles does not alter the cell volume. Various optical interactions which could account for light shielding are discussed.     

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.     

Pure culture growth of ectomycorrhizal fungi on inorganic nitrogen sources

Four ectomycorrhizal fungi were tested for their ability to grow (i.e., mycelial mat radial extension and fungal biomass) on nutrient media either supplemented with ammonium-nitrogen or nitrate-nitrogen or in the absence of an inorganic nitrogen source.Pisolithus tinctorius, Cenococcum geophilum andThelephora terrestris exhibited greater growth on ammonium-nitrogen.Suillus granulatus grew better on the nitrate-nitrogen nutrient medium. Regardless of inorganic nitrogen form preference (i.e., ammonium-nitrogen or nitrate-nitrogen), all 4 species showed some growth on each of the 3 nutrient media. Growth rate maxima varied by fungal species as well as by inorganic nitrogen source. Maximum growth rate forT. terrestris exceeded rates exhibited by the other 3 fungi by 2–5 times.     

Depth-related radiolarian assemblage in the water-column and surface sediments of the Japan Sea

Plankton tows and surface sediments from the Japan Sea, a marginal sea of the northwestern Pacific, were examined to study the depth distribution of modern radiolarians. The depth distribution patterns between the living assemblage in the water-column and the thanatocoenose in surface sediments are similar to each other, indicating that the depth-related assemblage in sediments is closely related to the living depths of major species. Four clear restrictions of many species to discrete depth zones are recognized in the water-column, from the surface down to 2000 m: (1) upper subsurface-water species, which are abundant from 40 to 120 m (Larcopyle butschlii juvenile form, Spirocyrtis subscalaris, Spongodiscus resurgens and Lipmanella virchowii); (2) lower subsurface-water species, which are abundant from 40 to 300 m (Larcopyle butschlii adult form, Ceratocyrtis histricosa and Spongotrochus glacialis); (3) intermediate-water species, which have population maxima from 160 to 300 m (Ceratospyris borealis); and (4) deep-water species, which have maxima between 1000 and 2000 m (Cycladophora davisiana and Actinomma boreale). Only a few specimens of A. boreale were found in the water-column ranging from 1000 to 2000 m depth, although this is a dominant species in surface sediments from depths below 2000 m of which the dominance increases with water depth. A. boreale may live mainly in the bottom water. Cycladophora davisiana and A. boreale, which characterize the Japan Sea deep assemblage, are naturally shallow or intermediate dwellers in other oceans. On the other hand, the typical deep-dwellers (e.g. Cornutella profunda, Cyrtopera languncula and Peripyramis circumtexta) of other oceans have not been found in the Japan Sea. Such a peculiar deep assemblage is a result of the deep circulation system in the Japan Sea and the shallow depths of the sills around it.     

Kinetics of the assembly of gas vacuoles in the blue-green alga Microcystis aeruginosa Kuetz. emend. Elekin.

Summary In exponentially growing cultures of the blue-green alga Microcystis aeruginosa the number of gas vacuoles per cell decreases and reaches a value of 4.5×10³ at 1.2×10⁷ cells per ml. The assembly of gas vacuoles with respect to number and length was followed after the organelles were caused to collapse by a pulse of ultrasound. The change in the number N of gas vacuoles per cell is N=224.8×t ^0.757, 0<t<24 h. After 24 h 50% of the value of non-sonicated cultures is reached. The changes in the length L of the organelles is expressed by L=87.06 ×t ^0.4084, 0<t<24 h. After 24 h 85% of the control value is reached.Abbreviations used EDTA ethylene diamine tetraacetate - BSA bovine serum albumine - P probability - N number of gas vacuoles - L length of gas vacuoles in nm - t time in hours     

Counting of gas vacuoles by electron microscopy in lysates and purified fractions ofmicrocystis aeruginosa

Summary A microdroplet spray method is described to determine quantitatively the number of gas vacuoles in purified fractions and in total lysates of the blue-green alga,Microcystis aeruginosa.It is found that 6.45×10¹² gas vacuoles of 370 nm length make up one mg of protein. This supports the idea that the entire organelle is made up by a single layer of protein only. The gas vacuole number per cell varies with the stage of growth between 3,700 and 11,000.     

The role of water level and salinity in the regulation of Juncus gerardi populations in former ricefields in southern France

Abstract. In the Rhône delta (southern France) Juncus gerardi is a dominant, strongly aggregating species in artificially flooded former rice fields. In order to explain this pattern, the effects of water depth, salinity and their interaction were measured on (1) seed germination and seedling development and (2) vegetative growth of J. gerardi in a controlled-environment experiment. The germination pattern of J. gerardi was affected by salinity. Low salinity (2 g/l NaCl) delayed germination while moderate salinity (12 g/l NaCl) reduced germination rate. In contrast, the germination of J. gerardi was not affected in the range of water depths tested (i.e. 0–10cm). Salinity negatively affected the development of below-ground parts, shoots and inflorescences. This negative effect of salinity on the vegetative growth of J. gerardi was amplified when combined with flooding. Flooding with fresh water (0–20 cm depth) did not limit biomass production during the experiment. However, a decrease in the ratio of below-ground/above-ground dry weight at deeper water depths suggests a limitation of the vegetative propagation of J. gerardi under prolonged flooding conditions. This hypothesis is supported by the negative correlation between the cover of J. gerardi and water depth found in an abandoned rice field. The limitation on seedling recruitment imposed by salinity and the depression of vegetative growth of J. gerardi due to a combination of salinity and water depth could explain the aggregate distribution of J. gerardi in former rice fields.     

Vertical movements through subsurface stream sediments by benthic macroinvertebrates during experimental drying are influenced by sediment characteristics and species traits

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Lifting the cloak of invisibility: the effects of changing optical conditions on pelagic crypsis

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Sporulation and further nutritional characteristics of Desulfotomaculum acetoxidans

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