Characterization,distribution, and significance ofMetallogenium in Lake Washington

During summer stratification,Metallogenium personatun was found exclusively in the hypolimnion of Lake Washington where the oxygen tension was below 8 ppm. Numbers of the organism decreased in the lake immediately following turnover in October. Significant concentrations ofMetallogenium microcolonies did not recur until spring, after the lake had stratified. During stratification the distribution of particulate manganese closely followed the distribution ofMetallogenium. EDAX analysis, confirmed by electron microprobe analyses of the encrustation, showed that the primary component was manganese. Iron and some trace elements were also precipitated on the organism but to a lesser degree. In addition, phosphate, the primary substance limiting phytoplankton growth in Lake Washington, was found in the encrustation, indicatingMetallogenium maybe important in limiting algal blooms in the lake. Attempts to growMetallogenium in the laboratory were unsuccessful. This inability, combined with the negative results of thin-sectioning and acridine orange staining ofMetallogenium microcolonies, suggests that the microcolonial structures seen in Lake Washington are not a living form of an organism.     

Production of Metallogenium-like particles by heterotrophic manganese-oxidizing bacteria collected from a lake

As a model of chemically stratified structure of environment typical to the chemocline of lakes, a semisolid gradient medium was prepared to cultivate heterotrophic manganese-oxidizing bacteria originally collected from a lake. The bacteria growing under the conditions described produced extracellularly Metallogenium-like particles similar to those which are often detected in the chemocline of lakes. This suggested that the naturally occurring Metallogenium-like particles originated in activities of such heterotrophic manganese-oxidizing bacteria. The manganese oxidation activity usually appeared only at the stationary phase of bacterial growth. The oxidation of Mn²⁺ and the formation of Metallogenium-like particles by the bacteria were observed at neutral or slightly acidic pH. not under alkaline conditions, which is a conspicuous difference from the inorganic oxidation of Mn²⁺ by O₂. Bacterial manganese oxidation was stimulated by bicarbonate (50 or 500 M). An experiment of addition of H₂O₂ to the incubation tubes isolated from atmosphere failed to confirm the availability of externally added H₂O₂ as the electron acceptor, suggesting that the bacterial manganese oxidation required the presence of O₂.     

Morphology,distribution and significance of the manganese-accumulating microorganism metallogenium in lakes

The manganese-accumulating microorganism Metallogenium is very common in the deep water and on the sediment surface in lakes of the Oslo district, southern Norway. Metallogenium accumulates manganese in its star-shaped coenobia; other trace metals are also greatly concentrated. The taxonomic position of the organism is uncertain. Sections of coenobia suggests that the encrusted parts are not enclosing living structures.In lake Nordbytjern, the occurrence of Metallogenium coincides with periods of turbulence in the lake. By sinking, the population accumulates close to the chemocline, becoming heavily encrusted. Plankton traps indicate that Metallogenium adds to the downward transport and accumulation of manganese and iron in the lake.     

Infection of procaryotic and eucaryotic microorganisms withMetallogenium

To elucidate the biological characteristics ofMetallogenium, a study was undertaken into the effect of infection of such organisms unable to oxidize manganese as fungi, yeasts, and bacteria with an ultrafiltrate of this organism on the subsequent behavior of the resulting binary cultures. The infection of microorganism cultures is accompanied by (a) acquisition by the binary cultures of a persistent capacity to oxidize manganese, (b) evolution of the characteristic structures ofMetallogenium (c) inhibition of the growth of the inoculated cultures; the inhibition manifests itself by fungi losing their capacity for spore formation and pigmentation, the upsetting of cell division processes, and lysis of the cells of the infected cultures all the way to death. When a heated ultrafiltrate ofMetallogenium was used to infect microorganism cultures, no signs of infection were detected.Metallogenium may be hosted by an extremely broad range of microorganisms that are in no way allied to one another. The experimental results suggest thatMetallogenium is an organism capable of parasitizing lower eucaryotic and procaryotic microorganisms. Analysis of 134 strains of fungi isolated from freshwater bodies is indicative of possible parasitism ofMetallogenium on microorganisms in their natural habitats.     

The Importance of the Manganese-Oxidizing Microorganism Metallogenium personatum for the Retention of Manganese in the Wahnbach Reservoir

The retention of manganese in the water of the Wahnbach reservoir was determined in mass balance calculations. The retention properties for manganese drastically decreased after the phosphorus elimination plant was taken into service. Processes controlling the distribution and mobility of manganese in the reservoir were based on the results of tests conducted to evaluate the role of the microorganism Metallogenium personatum. A substantial retention of manganese in the Wahnbach reservoir was found to be dependent on the presence of this planktonic manganese-oxidizing bacterium. The test results clearly indicate the importance of Metallogenium spec. as catalyst in the removal and oxidation of dissolved Mn(II).     

Distribution of iron- and manganese-oxidizing bacteria in the bottom sediments of Lake Baikal

The specific features of the distribution, abundance, and taxonomic diversity of bacteria oxidizing iron and manganese in the bottom sediments sampled from different areas of Lake Baikal are studied. These bacteria are widespread in Baikal bottom sediments. Cultivated iron- and manganese-oxidizing microorganisms are ascribed to six genera: Metallogenium, Leptothrix, Siderocapsa, Naumaniella, Bacillus, and Pseudomonas. The surface layers of the ground and the border between oxidized and reduced sediments serve as ecological niches for iron- and manganese-oxidizing microorganisms. Redox conditions of the environment and the availability of dissolved forms of iron and manganese, as well as of organic matter, which are controlled by the conditions of sedimentation in the lake, are the main factors affecting the abundance and distribution of iron bacteria.     

Co-introduction of Dolicirroplectanum lacustre,a monogenean gill parasite of the invasive Nile perch Lates niloticus: intraspecific diversification and mitonuclear discordance in native versus introduced areas

The Nile perch (Lates niloticus) is a notorious invasive species. The introductions of Nile perch into several lakes and rivers in the Lake Victoria region led to the impoverishment of trophic food webs, particularly well documented in Lake Victoria. Additionally, its parasites were co-introduced, including Dolicirroplectanum lacustre (Monogenea, Diplectanidae). Dolicirroplectanum lacustre is the single monogenean gill parasite of latid fishes (Lates spp.) inhabiting several major African freshwater systems. We examined the intra-specific diversification of D. lacustre from Lates niloticus in Lake Albert, Uganda (native range) and Lake Victoria (introduced range) by assessing morphological and genetic differentiation, and microhabitat preference. We expected reduced morphological and genetic diversity for D. lacustre in Lake Victoria compared with Lake Albert, as a result of the historical introductions. We found that D. lacustre displayed high morphological variability within and between African freshwaters, with two morphotypes identified, as in former studies. The single shared morphotype between Lake Albert and Lake Victoria displayed similar levels of haplotype and nucleotide diversity between the lakes. Mitonuclear discordance within the morphotypes of D. lacustre indicates an incomplete reproductive barrier between the morphotypes. The diversification in the mitochondrial gene portion is directly linked with the morphotypes, while the nuclear gene portions indicate conspecificity. Based on our results, we reported reduced genetic and morphological diversity, potentially being a result of a founder effect in Lake Victoria.     

Multiple generalist morphs of Lake Trout: Avoiding constraints on the evolution of intraspecific divergence?

A generalist strategy, as an adaptation to environmental heterogeneity, is common in Arctic freshwater systems, often accompanied, however, by intraspecific divergence that promotes specialization in niche use. To better understand how resources may be partitioned in a northern system that supports intraspecific diversity of Lake Trout, trophic niches were compared among four shallow‐water morphotypes in Great Bear Lake (N65^° 56′ 39″, W120^° 50′ 59″). Bayesian mixing model analyses of stable isotopes of carbon and nitrogen were conducted on adult Lake Trout. Major niche overlap in resource use among four Lake Trout morphotypes was found within littoral and pelagic zones, which raises the question of how such polymorphism can be sustained among opportunistic generalist morphotypes. Covariances of our morphological datasets were tested against δ¹³C and δ¹⁵N values. Patterns among morphotypes were mainly observed for δ¹⁵N. This link between ecological and morphological differentiation suggested that selection pressure(s) operate at the trophic level (δ¹⁵N), independent of habitat, rather than along the habitat‐foraging opportunity axis (δ¹³C). The spatial and temporal variability of resources in Arctic lakes, such as Great Bear Lake, may have favored the presence of multiple generalists showing different degrees of omnivory along a weak benthic–pelagic gradient. Morphs 1–3 had more generalist feeding habits using both benthic and pelagic habitats than Morph 4, which was a top‐predator specialist in the pelagic habitat. Evidence for frequent cannibalism in Great Bear Lake was found across all four morphotypes and may also contribute to polymorphism. We suggest that the multiple generalist morphs described here from Great Bear Lake are a unique expression of diversity due to the presumed constraints on the evolution of generalists and contrast with the development of multiple specialists, the standard response to intraspecific divergence.     

Spatial and temporal distribution of Caulobacter spp. in two mesotrophic lakes

The seasonal distribution of Caulobacter spp. has been determined in the water column of two mesotrophic lakes using most probable number (MPN) viable counting techniques from April, 1972 to March, 1973. Concentrations in Lake Washington, a monomictic lake, peaked at 1000–3300 per ml in the epilimnion during the late spring and summer and reached lows in October of less than 2 per ml prior to fall turnover. The reason for the decrease in viable numbers is not known. Caulobacter spp. began to increase gradually in December, during the winter mixing period well before the spring bloom. Concentrations in Hall Lake, a small kettle lake, were somewhat higher than in Lake Washington, ranging from 0.27 per ml in October to over 5000 per ml during May. In contrast to Lake Washington, the highest populations were found in the metalimnion and upper hypolimnion of Hall Lake. Caulobacter spp. were also found in the anaerobic depths of the hypolimnion. However, these did not grow anaerobically, suggesting that they had settled into the hypolimnion and survived in the cold anaerobic zone. The populations of Caulobacter spp. reached maximum numbers at the approximate times and depths at which algal biomass would be expected to be greatest.     

Formation of Metallogenium-like structures by a manganese-oxiding fungus

Structures resembling Metallogenium spp. were observed in agar and in liquid cultures of a Mn-oxidizing basidiomycetous fungus only when Mn²⁺ was oxidized. Fungal viability was necessary for formation of the structures; Mn²⁺ concentration and the presence or absence of agar in the medium were important factors determining their morphology. Slide cultures revealed no identifiable cells in any stage of development. Fluorescent dyes that stained nucleic acids and polysaccharides in the fungal hyphae did not stain the Metallogenium-like structures. Likewise, Rhodamine 123, a fluorescent probe for membrane potential, stained fungal mitochondria, but did not stain the structures. Thin sections through the structures showed no biological membranes or other cellular features. Only the characteristic ultrastructure of biological Mn oxides were observed in serial thin sections. In agar, unfixed structures disappeared permanently during reduction of Mn oxides with hydroxylamine. Glutaraldehyde fixation stabilized these structures. Fixed structures lost most of their original phase density during reduction with hydroxylamine, but continuous microscopic observations showed that their phase density could be restored by staining with Coomassie blue. Structures that formed in liquid medium did not require stabilization with glutaraldehyde during reduction of Mn oxides. They, too, lost their original phase density during reduction with hydroxylamine; phase density could be restored by staining with cationic colloidal iron or Coomassie blue. The results suggest that the Metallogenium-like structures were formed as a result of Mn oxidation associated with exopolymers produced by the fungus.Non-standard abbreviations HEPES (N-hydroxyethylpiperazine-N-2-ethane sulfonic acid) - DAPI (4,6-diamidino-2-phenylindole) - PIPES (piperazine-N,N-bis[2-ethane sulfonic acid])     

Raphidiopsis mediterranea Skuja represents non-heterocytous life-cycle stages of Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju in Lake Kastoria (Greece), its type locality: Evidence by morphological and phylogenetic analysis

The taxonomical relationship of Cylindrospermopsis raciborskii and Raphidiopsis mediterranea was studied by morphological and 16S rRNA gene diversity analyses of natural populations from Lake Kastoria, Greece. Samples were obtained during a bloom (23,830 trichomes mL⁻¹) in August 2003. A high diversity of apical cell, trichome, heterocyte and akinete morphology, trichome fragmentation and reproduction was observed. Trichomes were grouped into three dominant morphotypes: the typical and the non-heterocytous morphotype of C. raciborskii and the typical morphotype of R. mediterranea. A morphometric comparison of the dominant morphotypes showed significant differences in mean values of cell and trichome sizes despite the high overlap in the range of the respective size values. Additionally, two new morphotypes representing developmental stages of the species are described while a new mode of reproduction involving a structurally distinct reproductive cell is described for the first time in planktic Nostocales. A putative life-cycle, common for C. raciborskii and R. mediterranea is proposed revealing that trichome reproduction of R. mediterranea gives rise both to R. mediterranea and C. raciborskii non-heterocytous morphotypes. The phylogenetic analysis of partial 16S rRNA gene (ca. 920 bp) of the co-existing Cylindrospermopsis and Raphidiopsis morphotypes revealed only one phylotype which showed 99.54% similarity to R. mediterranea HB2 (China) and 99.19% similarity to C. raciborskii form 1 (Australia). We propose that all morphotypes comprised stages of the life cycle of C. raciborkii whereas R. mediterranea from Lake Kastoria (its type locality) represents non-heterocytous stages of Cylindrospermopsis complex life cycle.     

The manganese cycle in Lac Léman,Switzerland: the role ofMetallogenium

The manganese pathways in Lac Léman have been investigated on the basis of chemical analyses undertaken on water, suspended solids, bottom sediments and interstitial water samples. The various modes of occurrence of Mn have been determined by means of visual examination using SEM and TEM (scanning and transmission electron microscopy), by microanalysis (EDAX) of various sediment fractions, by chemical analysis of the dissolved phase, and by chemical speciation and XRD of bottom sediments. Fluxes to and from the sediment have also been computed. The time-depth variations of Mn in the water column are characterized by (a) a very steep gradient of Mn sol. from the sediment interstitial water (15 mg l⁻¹) to the overlying water, 2 m above the bottom(500 μg l⁻¹), (b) an accumulation of Mn part. between 280 m and the interface at 310 m, consisting of mineralized colonies ofMetallogenium. The abundance ofMetallogenium colonies is inversely related to O₂ concentration; the optimal value for the bacterium Mn fixation is around 1 mg l⁻¹. Because of the quasi-anoxic state of the bottom sediments and overlying water, Mn diffuses from a ‘source layer’, 2–5 cm below the interface (a) upwards across the interface, before being taken up byMetallogenium, and (b) downwards to a ‘sink layer’, in which large amounts of Mn-carbonate precipitate. Particulate Mn sedimentation rates measured in traps show that downwards Mn flux due toMetallogenium settling approximately balances the upwards soluble flux due to diffusion. Quantitatively, the process of Mn cycling in Lac Léman is, therefore, limited to the lowermost part of the hypolimnion. Although Zn and Cd seem to follow the same cycle as Mn, Fe behaves in a different manner; it was not taken up byMetallogenium at the time of our study.     

Manganese Oxidation by Spores and Spore Coats of a Marine Bacillus Species

Bacillus sp. strain SG-1 is a marine bacterial species isolated from a near-shore manganese sediment sample. Its mature dormant spores promote the oxidation of Mn²⁺ to MnO₂. By quantifying the amounts of immobilized and oxidized manganese, it was established that bound manganese was almost instantaneously oxidized. When the final oxidation of manganese by the spores was partly inhibited by NaN₃ or anaerobiosis, an equivalent decrease in manganese immobilization was observed. After formation of a certain amount of MnO₂ by the spores, the oxidation rate decreased. A maximal encrustment was observed after which no further oxidation occurred. The oxidizing activity could be recovered by reduction of the MnO₂ with hydroxylamine. Once the spores were encrusted, they could bind significant amounts of manganese, even when no oxidation occurred. Purified spore coat preparations oxidized manganese at the same rate as intact spores. During the oxidation of manganese in spore coat preparations, molecular oxygen was consumed and protons were liberated. The data indicate that a spore coat component promoted the oxidation of Mn²⁺ in a biologically catalyzed process, after adsorption of the ion to incipiently formed MnO₂. Eventually, when large amounts of MnO₂ were allowed to accumulate, the active sites were masked and further oxidation was prevented.     

Spatial distribution and morphologic diversity of virioplankton in Lake Donghu, China

The spatial distribution and morphological diversity of virioplankton were determined in Lake Donghu which contains three trophic regions: hypertrophic, eutrophic and mesotrophic region. Virioplankton abundance measured by transmission electron microscope (TEM) ranged from 7.7 × 10⁸ to 3.0 × 10⁹ ml^–1, being among the highest observed in any natural aquatic system examined so far. The spatial distribution of virioplankton was correlated significantly with chlorophyll a concentration (r = 0.847; P < 0.01) at the sampling sites in Lake Donghu. 76 morphotypes were observed. Most morphotypes have tails, belonging to Siphoviridae, Myoviridae and Podoviridae. The majority of tailed phages in the lake were Myoviridae. Morphotypes which were rarely reported, such as prolate-headed virus-like particles, lemon-shaped virus-like particle, and viruses resembling Tectiviridae and Corticoviridae were all observed in the lake. It is concluded that the high viral abundance might be associated with high density of phytoplankton including algae and cyanobacteria. There was high viral diversity in this eutrophic shallow lake. In addition, cyanophage represented an important fraction of the virioplankton community in Lake Donghu.     

Identification of the maternal source of young‐of‐the‐year Arctic charr in Lake Hazen,Canada

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Variations in Abundance,Genome Size,Morphology, and Functional Role of the Virioplankton in Lakes Annecy and Bourget over a 1-Year Period

We sampled the surface waters (2–50 m) of two deep peri-alpine lakes over a 1-year period in order to examine (1) the abundance, vertical distribution, genome size, and morphology structures of the virioplankton; (2) the virus-mediated bacterial mortality; and (3) the specific genome size range of double-stranded DNA (dsDNA) phytoplankton viruses. Virus-like particle (VLP) concentrations varied between 4.16?×?10⁷ (January) and 2.08?×?10⁸ part mL^?1 (May) in Lake Bourget and between 2.7?×?10⁷ (June) and 8.39?×?10⁷ part mL^?1 (November) in Lake Annecy. Our flow cytometry analysis revealed at least three viral groups (referred to as virus-like particles 1, 2, and 3) that exhibited distinctive dynamics suggestive of different host types. Phage-induced bacterial mortality varied between 6.1 % (June) and 33.2 % (October) in Lake Bourget and between 7.4 % (June) and 52.6 % (November) in Lake Annecy, suggesting that viral lysis may be a key cause of mortality of the bacterioplankton. Virioplankton genome size ranged from 27 to 486 kb in Lake Bourget, while it reached 620 kb in Lake Annecy for which larger genome sizes were recorded. Our analysis of pulsed field gel electrophoresis bands using different PCR primers targeting both cyanophages and algal viruses showed that (1) dsDNA viruses infecting phytoplankton may range from 65 to 486 kb, and (2) both cyanophage and algal “diversity” were higher in Lake Annecy. Lakes Annecy and Bourget also differed regarding the proportions of both viral families (with the dominance of myoviruses vs. podoviruses) and infected bacterial morphotypes (short rods vs. elongated rods), in each of these lakes, respectively. Overall, our results reveal that (1) viruses displayed distinct temporal and vertical distribution, dynamics, community structure in terms of genome size and morphology, and viral activity in the two lakes; (2) the Myoviridae seemed to be the main cause of bacterial mortality in both lakes and this group seemed to be related to VLP2; and (3) phytoplankton viruses may have a broader range of genome size than previously thought. This study adds to growing evidence that viruses are diverse and play a significant role in freshwater microbial dynamics and more globally lake functioning. It highlights the importance of further considering this biological compartment for a better understanding of plankton ecology in peri-alpine lakes.     

Silver Nanoparticles for the Adsorption of Manganese from Biological Samples

In this study, silver nanoparticles were prepared and used for separation and preconcentration of manganese from biological samples. The technical feasibility of silver nanoparticles for manganese removal was investigated under batch studies. The effects of different parameters such as pH of solution, time (t), amounts of PAN (E), and silver nanoparticles (N) on the adsorption of manganese by silver nanoparticle were investigated using factorial design and response surface methodology based on Box–Behnken design. Thermodynamic parameters indicate the adsorption process to be exothermic. The limit of detection of the proposed method followed by inductively coupled plasma was found to be 0.08?µg L^?1. The method was applied to determine of manganese in biological samples.     

Evolution and origin of sympatric shallow-water morphotypes of Lake Trout,Salvelinus namaycush,in Canada's Great Bear Lake

Range expansion in north-temperate fishes subsequent to the retreat of the Wisconsinan glaciers has resulted in the rapid colonization of previously unexploited, heterogeneous habitats and, in many situations, secondary contact among conspecific lineages that were once previously isolated. Such ecological opportunity coupled with reduced competition likely promoted morphological and genetic differentiation within and among post-glacial fish populations. Discrete morphological forms existing in sympatry, for example, have now been described in many species, yet few studies have directly assessed the association between morphological and genetic variation. Morphotypes of Lake Trout, Salvelinus namaycush, are found in several large-lake systems including Great Bear Lake (GBL), Northwest Territories, Canada, where several shallow-water forms are known. Here, we assess microsatellite and mitochondrial DNA variation among four morphotypes of Lake Trout from the five distinct arms of GBL, and also from locations outside of this system to evaluate several hypotheses concerning the evolution of morphological variation in this species. Our data indicate that morphotypes of Lake Trout from GBL are genetically differentiated from one another, yet the morphotypes are still genetically more similar to one another compared with populations from outside of this system. Furthermore, our data suggest that Lake Trout colonized GBL following dispersal from a single glacial refugium (the Mississippian) and support an intra-lake model of divergence. Overall, our study provides insights into the origins of morphological and genetic variation in post-glacial populations of fishes and provides benchmarks important for monitoring Lake Trout biodiversity in a region thought to be disproportionately susceptible to impacts from climate change.     

Taxonomy and phenotypic relationships of the Anastrepha fraterculus complex in the Mesoamerican and Pacific Neotropical dominions (Diptera,Tephritidae)

Previous morphometric studies based on linear measurements of female structures of the aculeus, mesonotum, and wing revealed the existence of seven morphotypes within the Anastrepha fraterculus cryptic species complex along the Neotropical Region. The current research followed linear and geometric morphometric approaches in 40 population samples of the nominal species Anastrepha fraterculus (Wiedemann) spread throughout the Meso-American and Pacific Neotropical dominions (including Mexico, Central America, Venezuela, Colombia, Ecuador, and Peru). The goals were to explore the phenotypic relationships of the morphotypes in these biogeographical areas; evaluate the reliability of procedures used for delimitation of morphotypes; and describe their current distribution. Findings determined that morphotypes previously recognized via the linear morphometrics were also supported by geometric morphometrics of the wing shape. In addition, we found an eighth morphotype inhabiting the highlands of Ecuador and Peru. Morphotypes are related into three natural phenotypic groups nominated as Mesoamerican-Caribbean lineage, Andean lineage, and Brazilian lineage. The hypothesis that lineages are not directly related to each other is discussed, supported by their large morphological divergence and endemicity in these three well-defined biogeographic areas. In addition, this hypothesis of the non-monophyly of the Anastrepha fraterculus complex is also supported by evidence from other authors based on molecular studies and the strong reproductive isolation between morphs from different lineages.     

Kinetics of Manganese Oxidation by Cell-Free Extracts of Bacteria Isolated from Manganese Concretions from Soil

A study of the kinetics of Mn²⁺ oxidation catalyzed by cell extracts of two bacterial isolates (E₁, Pseudomonas III [new isolate] and E₄, Citrobacter freundii) isolated from the core of manganese concretions from Greek soils is presented. The reaction velocity of Mn²⁺ oxidation was determined from the rate of consumption of Mn²⁺. The oxidation of Mn²⁺ was followed by measuring changes in Mn²⁺ concentration by activation analysis and by atomic absorption spectrophotometry. The reaction velocity was directly proportional to cell extract concentration when the reaction time was 1 h. At longer reaction times, the relationship deviated from linearity because substrate concentration became limiting. The rate of Mn²⁺ oxidation increased with the Mn²⁺ concentration. Analysis of the results by application of the integrated Michaelis equation for determining Michaelis constants and maximal velocities either in the presence (K_m = 3.33 μmol/ml and V_max = 1.25 μmol/ml·h) or in the absence of maleate buffer (K_m = 2.52 μmol/ml and V_max = 2.04 μmol/ml·h) indicated a strong affinity between the oxidizing system and manganese. All results in this study are consistent with an enzymatic manganese-oxidizing system and give an indication of the mechanism of biological Mn²⁺ oxidation in soil which differs from that in the marine environment.