Search

Free-living amoebae (FLA) are found in diverse environments, such as soils, rivers, and seas. Hence, they can be used as bioindicators to assess the water quality based solely on their presence. In this study, we determined the presence of FLA in river water by filtering water samples collected from various sites and culturing the resulting filtrates. FLA were detected in all the water samples with varying quality grades (Grades I-V). The significant increase in the size of the amoebae population with the deterioration in the water quality. Monoxenic cultures of the amoebae were performed, and genomic DNAs were isolated, among which 18S rDNAs were sequenced to identify the amoeba species. Of the 12 species identified, 10 belonged to the Acanthamoeba genus; of the remaining 2 species, one was identified as Vannella croatica and the other as a species of Vermamoeba. Acanthamoeba was detected in samples with Grades I to VI quality, whereas the Vermamoeba species was present only in Grade I water. V. croatica was found exclusively in water with Grade II quality. Following morphological observations, genomic DNA was sequenced using 16S rDNA to determine whether the species of Acanthamoeba harbored endosymbionts. Most of the isolated Acanthamoeba contained endosymbionts, among which 4 species of endogenous bacteria were identified and examined using transmission electron microscopy. This study provides evidence that the distribution of amoebae other than Acanthamoeba may be associated with water quality. However, further confirmation will be required based on accurate water quality ratings and assessments using a more diverse range of FLA. [ABSTRACT FROM AUTHOR]

Free-living amoebae (FLA) rarely cause human infections but can invoke fatal infections in the central nervous system (CNS). No consensus treatment has been established for FLA infections of the CNS, emphasizing the urgent need to discover or develop safe and effective drugs. Flavonoids, natural compounds from plants and plant-derived products, are known to have antiprotozoan activities against several pathogenic protozoa parasites. The anti-FLA activity of flavonoids has also been proposed, while their antiamoebic activity for FLA needs to be emperically determined. We herein evaluated the antiamoebic activities of 18 flavonoids against Naegleria fowleri and Acanthamoeba species which included A. castellanii and A. polyphaga. These flavonoids showed different profiles of antiamoebic activity against N. fowleri and Acanthamoeba species. Demethoxycurcumin, kaempferol, resveratrol, and silybin (A+B) showed in vitro antiamoebic activity against both N. fowleri and Acanthamoeba species. Apigenin, costunolide, (‒)-epicatechin, (‒)-epigallocatechin, rosmarinic acid, and (‒)-trans-caryophyllene showed selective antiamoebic activity for Acanthamoeba species. Luteolin was more effective for N. fowleri. However, afzelin, berberine, (±)-catechin, chelerythrine, genistein, (+)-pinostrobin, and quercetin did not exhibit antiamoebic activity against the amoeba species. They neither showed selective antiamoebic activity with significant cytotoxicity to C6 glial cells. Our results provide a basis for the anti-FLA activity of flavonoids, which can be applied to develope alternative or supplemental therapeutic agents for FLA infections of the CNS. [ABSTRACT FROM AUTHOR]

Peatlands cover 3% of the earth’s land surface but contain 30% of the world’s soil carbon pool. Microbial communities constitute a crucial detrital food web for nutrient and carbon cycling in peatlands. Heterotrophic protozoans are considered top predators in the microbial food web; however, they are not yet well understood. In this study, we investigated seasonal dynamics in the community and the trophic structure of testate amoebae in four peatlands. Testate amoebae density and biomass in August were significantly higher than those in May and October. The highest density, 6.7 × 10 4 individual g −1 dry moss, was recorded in August 2014. The highest biomass, 7.7 × 10 2  μg C g −1 dry moss, was recorded in August 2013. Redundancy analyses showed that water-table depth was the most important factor, explaining over one third of the variance in fauna communities in all sampled seasons. High trophic position taxa dominated testate amoebae communities. The Shannon diversity index and community size structure index declined from August to October in 2013 and from May to October in 2014. These seasonal patterns of testate amoebae indicated the seasonal variations of the peatlands’ microbial food web and are possibly related to the seasonal carbon dynamics in Northeast Chinese peatlands. [ABSTRACT FROM AUTHOR]

Legionella was monitored in reclaimed water systems and were detected by culture in 50% of 115 samples, while 80% of the samples were positive by quantitative polymerase chain reaction (qPCR). The lowest level of Legionella was in a system that practiced biological nutrient removal and maintained an average 0.3 mg/L free chlorine residual. The difference between qPCR and ethidium monoazide treated samples was used as an indicator of viability, and the greatest difference was in a chloraminated system, where the molecular method indicated a 9% viability. Ninety-six percent of the species were L. pneumophila, and 87% were identified as L. pneumophila serotype 1. Total amoebae (summed as cysts or trophozoites) were detected in 100% of samples from all six systems, and were mostly (50–95%) in the active trophozoite phase. In the chloraminated system, 87% of the mesophilic amoebae and 66% of the thermophilic amoebae were in the cyst phase. [ABSTRACT FROM AUTHOR]

The genus Kraken represents a distinct lineage of filose amoebae within the Cercozoa. Currently a single species, Kraken carinae , has been described. SSU rDNA phylogeny showed an affiliation to the Cercomonadida, branching with weak support at its base, close to Paracercomonas , Metabolomonas , and Brevimastigomonas . Light microscopical analyses showed several unique features of the genus Kraken , but ultrastructure data were lacking. In this study, K. carinae has been studied by electron microscopy, these data conjoined with a two-gene phylogeny were used to give more insight into the evolutionary relationship of the genus Kraken within Cercozoa. The data confirmed the absence of flagella, but also showed novel characteristics, such as the presence of extrusomes, osmiophilic bodies, and mitochondria with flat cristae. Surprising was the presence of single-tier scales which are carried by cell outgrowths, much of what is expected of the last common ancestor of the class Imbricatea. The phylogenetic analyses however confirmed previous results, indicating Kraken as a sister group to Paracercomonas in Sarcomonadea with an increased but still low support of 0.98 PP/63 BP. Based on the unique features of Kraken we establish the Krakenidae fam. nov. that we, due to contradictory results in morphology and phylogeny, assign incertae sedis, Monadofilosa. [ABSTRACT FROM AUTHOR]

Although testate amoebae have attracted great interest of protistologists for more than a century, some groups, especially those with a hyaline, organic test (=theca) are still poorly known. One of those is the genus Lecythium Hertwig et Lesser, 1874. Only recently Lecythium spp. were characterized by morphological and molecular means, but data on the type species Lecythium hyalinum Hertwig et Lesser, 1874, was still lacking. In this study, we screened for L. hyalinum in freshwater samples of Germany and the Netherlands. Four different isolates of L. hyalinum and one novel species were cultured and characterized by light microscopy. Phylogenetic analyses based on the small ribosomal subunit (SSU) RNA gene show that the genus Lecythium forms two robust clades, one forming a sister group to the Rhizaspididae/Pseudodifflugiidae clade (Tectofilosida), the other branching within ‘Novel Clade 4’ (Tectofilosida). We untangle this polyphyly by establishing Fisculla gen. nov. and the Fiscullidae fam. nov. for the former of these two clades. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ecological studies of peatland testate amoebae are generally based on totals of 150 individuals per sample. However, the suitability of this standard has never been assessed for alkaline habitats such as spring fens. We explored the differences in testate amoeba diversity between Sphagnum and brown-moss microhabitats at a mire site with a highly diversified moss layer which reflects the small-scale heterogeneity in groundwater chemistry. Relationships between sampling efficiency and sample completeness were explored using individual-based species accumulation curves and the effort required to gain an extra species was assessed. Testate amoeba diversity differed substantially between microhabitats, with brown mosses hosting on average twice as many species and requiring greater shell totals to reach comparable sample analysis efficiency as for Sphagnum . Thus, for samples from alkaline conditions an increase in shell totals would be required and even an overall doubling up to 300 individuals might be considered for reliable community description. Our small-scale data are likely not robust enough to provide an ultimate solution for the optimization of shell totals. However, the results proved that testate amoebae communities from acidic and alkaline environments differ sharply in both species richness and composition and they might call for different methodological approaches. [ABSTRACT FROM AUTHOR]

The diversity of heterolobosean amoebae, important members of soil, marine and freshwater microeukaryote communities in the temperate zones, is greatly under-explored in high latitudes. To address this imbalance, we studied the diversity of this group of free-living amoebae in the Arctic and the Antarctic using culture dependent methods. Eighteen strain representatives of three heterolobosean genera, Allovahlkampfia Walochnik et Mulec, 2009 (1 strain), Vahlkampfia Chatton et Lalung-Bonnaier, 1912 (2) and Naegleria Alexeieff, 1912 (15) were isolated from 179 samples of wet soil and fresh water with sediments collected in 6 localities. The Allovahkampfia strain is the first representative of the genus from the Antarctic; 14 strains (7 from the Arctic, 7 from the Antarctic) of the highly represented genus Naegleria complete the ‘polar’ cluster of five Naegleria species previously known from the Arctic and Sub-Antarctic regions, whereas one strain enriches the ‘dobsoni’ cluster of Naegleria strains of diverse origin. Present isolations of Naegleria polaris De Jonckheere, 2006 from Svalbard, in the Arctic and Vega Island, in the Antarctic and N . neopolaris De Jonckheere, 2006 from Svalbard and Greenland in the Arctic, and James Ross Island, the Antarctic demonstrate their bipolar distribution, which in free-living amoebae has so far only been known for Vermistella Morand et Anderson, 2007. [ABSTRACT FROM AUTHOR]

Testate amoebae with self-secreted siliceous shell platelets (“idiosomes”) play an important role in terrestrial silicon (Si) cycles. In this context, Si-dependent culture growth dynamics of idiosomic testate amoebae are of interest. Clonal cultures of idiosomic testate amoebae were analyzed under three different Si concentrations: low (50 μmol L −1 ), moderate/site-specific (150 μmol L −1 ) and high Si supply (500 μmol L −1 ). Food ( Saccharomyces cerevisiae ) was provided in surplus. (i) Shell size of four different clones of idiosomic testate amoebae either decreased ( Trinema galeata , Euglypha filifera cf.), increased ( E. rotunda cf.), or did not change ( E. rotunda ) under the lowest Si concentration (50 μmol Si L −1 ). (ii) Culture growth of idiosomic Euglypha rotunda was dependent on Si concentration. The more Si available in the culture medium, the earlier the entry into exponential growth phase. (iii) Culture growth of idiosomic Euglypha rotunda was dependent on origin of inoculum. Amoebae previously cultured under a moderate Si concentration revealed highest sustainability in consecutive cultures. Amoebae derived from cultures with high Si concentrations showed rapid culture growth which finished early in consecutive cultures. (iv) Si (diluted in the culture medium) was absorbed by amoebae and fixed in the amoeba shells resulting in decreased Si concentrations. [ABSTRACT FROM AUTHOR]

Amoebae of the genus Korotnevella are covered with scales, the structure of which is believed to be species–specific and allows distinguishing species reliably at the morphological level. We studied members of this genus in order to assess the genetic structure of the local populations of amoebae. For the present study we isolated nine freshwater strains of Korotnevella , belonging to three species, from two locations in North-Western Russia. In order to obtain data on the population structure of these amoebae, we identified all isolates based on the light-microscopic morphology and scale structure and investigated both inter-strain and intra-strain polymorphism of Cox I and 18S rRNA genes. Results show that both genes provide congruent patterns of population structure. The Cox I gene appears to be more reliable DNA barcode while the 18S rRNA gene shows an interesting pattern of polymorphism, which may represent phylotypes of amoebae. Local population of amoebae in every studied species consists of a number of genetic lineages (phylotypes), some shared between the populations while others are unique to a local habitat. [ABSTRACT FROM AUTHOR]

Although the presence of test is the most fundamental synapomorphy of arcellinid lobose amoebae, the significance of tests in maintenance of the biological functions of these organisms is still largely unclear. This paper demonstrates the effect of the artificial test removal on the behaviour, ultrastructure and reproduction of the testate lobose amoebae belonging to the two species of the genus Arcella . The studied cells can survive after artificial removal of their test, and many specimens are capable of building a test de novo. We investigated this process and found that test-free cells of Arcella in culture remained alive for weeks; they are able to move and feed, but never undergo normal cell division accompanied by mitosis. Test-free cells can restore the test in three different ways: (1) building almost normal test; (2) building a very small single-chambered test; (3) building a test which consisted of several small chambers attached to each other. Although newly constructed tests are abnormal, cells restore shape, size and other characteristic features of the test in the next one or two generations of descendants. The results obtained suggest that the test may be critically important for completing a life cycle of an amoeba. [ABSTRACT FROM AUTHOR]

Mountainous peatlands of Western Sudetes are considered a unique habitat in Central Europe. The region contains one of the largest raised bog complexes in temperate Europe and is thus of great importance for biodiversity conservation. In this first high-resolution study from this region we use long-term ecological data to assess how these mountain wetland ecosystems responded to anthropogenic impacts and climate change. We used testate amoebae morphological traits, micro- and macroscopic charcoal, pollen and plant macrofossils to reconstruct the history of peatland development over 800 years, illustrating shifts in its development and fire dynamics. Five hydrological stages of peatland development were recognized. Testate amoebae morphological traits reflected several abrupt ecological changes linked to anthropogenic modifications of landscape openness. A shift towards mixotrophic taxa, linked to hydrological change or shrubs expansion and shading, preceded aperture position change, which was associated to dust input through surrounding deforestation and simultaneous water-table increase. Fire reconstruction revealed increasing burning together with intensifying human activity, including the expansion of a nearby settlement. This study confirms the potential of testate amoeba communities and the use of morpho-functional traits as indicators of ecological effects of land-use change over long-temporal scales. [ABSTRACT FROM AUTHOR]

We present the first detailed analysis of subfossil testate amoebae from a tropical peatland. Testate amoebae were analysed in a 4-m peat core from western Amazonia (Peru) and a transfer function developed from the site was applied to reconstruct changes in water table over the past ca. 8,000 years. Testate amoebae were in very low abundance in the core, especially in the lower 125 cm, due to a combination of poor preservation and obscuration by other organic matter. A modified preparation method enabled at least 50 testate amoebae to be counted in each core sample. The most abundant taxa preserved include Centropyxis aculeata , Hyalosphenia subflava , Phryganella acropodia and Trigonopyxis arcula . Centropyxis aculeata , an unambiguous wet indicator, is variably present and indicates several phases of near-surface water table. Our work shows that even degraded, low-abundance assemblages of testate amoebae can provide useful information regarding the long-term ecohydrological developmental history of tropical peatlands. [ABSTRACT FROM AUTHOR]

Cryptotephra (particles <125 μm) is a key record for monitoring past and current volcanic activity. However, its extraction from the host sediment and analysis is often long and difficult because of its small size. Finding a simple method to extract cryptotephra from environmental samples would therefore make its analysis much easier. We hypothesized that arcellinid testate amoebae may hold such a potential. These free-living shelled protists are among the earliest microorganisms to colonize volcanic tephra, and build their shell by agglutinating minerals from their environment. We analyzed by X-ray Spectrometry the mineral signature of tephra from the 2011 Puyehue-Cordon Caulle Volcanic Complex (Chile) eruption ash fallout and compared it to that of the shells of 51 individual testate amoebae (three individuals from each of 17 species) from 13 samples collected at different distances from the active vent. The mineral composition of particles within shells closely matched that of similar size class particles from their environment. The capacity of testate amoebae to randomly use mineral grains from their environment makes it possible to use their shells to assess the mineral composition of cryptotephra from soil, peat or sediment samples. Testate amoebae therefore represent the microbial world's version of Cinderella's helping pigeons. [ABSTRACT FROM AUTHOR]

Testate amoebae are a polyphyletic assemblage of at least three major, unrelated taxonomic groups of unicellular amoeboid eukaryotes exhibiting a test. The focus on testate amoebae in scientific research has greatly increased in the past 20 years: from an average of about 5 papers a year in the mid-1990s to the current rate of more than 50 papers published yearly. The application range of these organisms is rapidly expanding as well: from the traditional fields of environmental monitoring and paleoecology, to forensic sciences and ecotoxicology studies. These developments are nevertheless strongly dependent on reliable taxonomy and nomenclature. However, scientometric data reveal that despite an ever-increasing necessity for the use of names (the product of taxonomy), the corresponding effort has not been achieved for improving testate amoebae systematics. As a consequence, inaccurate taxonomy yields to misinterpretations in the diversity of the organisms and to potentially incorrect conclusions. These and related problems are discussed in this study, highlighting the outcome of poor taxonomic expertise in accurate classification and phylogeny of testate amoebae, and the consequences derived from it. Additionally, this study is aimed to discuss the current status of testate amoebae classification, and to present all nomenclature and taxonomic changes in higher and lower taxonomic levels of testate amoebae, as a result of recent molecular reconstructions. Finally, we conclude with a list of the needs and suggestions toward a unified and modernized taxonomy of testate amoebae. [ABSTRACT FROM AUTHOR]

The present paper describes two new species of lobose amoebae belonging to the family Paramoebidae within the order Dactylopodida: Pseudoparamoeba microlepis n. sp. and Korotnevella fousta n. sp. Among them, P. microlepis formally fits the diagnosis of the genus Korotnevella , because it has scales and lacks a parasome. At the same time its 18S rDNA gene sequence robustly groups with Pseudoparamoeba pagei and never branches among those of Korotnevella spp. Korotnevella fousta in 18S rDNA tree groups among other species of the genus Korotnevella . It has uniform scales with an elliptical basal plate and spine arising from its central part and surrounded by an “inverted skirt” structure. These findings show that the current differentiation between the genera Korotnevella and Pseudoparamoeba based on the presence of scales is not entirely valid. At the moment only molecular data can reliably differentiate these two genera. [ABSTRACT FROM AUTHOR]

Testate amoebae have been frequently studied by protistologists, but still little information is available on some groups like the Chlamydophryidae. These amoebae are difficult to culture and therefore quantitative information on their morphology, phylogeny and ecology is scarce. We isolated and cultured a small testate amoeba from an agricultural field at Müncheberg near Berlin, Germany. Morphological analyses revealed it to be a new species of the genus Lecythium . We describe Lecythium terrestris sp. nov. and present its morphology, mycophagous and algivorous feeding habits and its ability to form cell aggregates by fusion. Using small-subunit ribosomal RNA gene phylogeny, we could confirm the phylogenetic position of the genus Lecythium among the Cercozoa where it groups closely to Pseudodifflugiidae (Tectofilosida). [ABSTRACT FROM AUTHOR]

Testate amoebae are an abundant group of microorganisms which make a significant contribution to the diversity of protist life. Most of the world's potential habitats for testate amoebae have been barely studied and when such places are investigated they frequently reveal novel communities and species. Here we consider the testate amoeba communities associated with boreal forest epiphytes (mosses and lichens); an environment which we argue has been under-researched. We present a dataset of 165 samples from four regions of western Russia and analyse these data in relation to micro-habitat position and selected environmental data. The testate amoebae of epiphytes are abundant but dominated by ubiquitous species. We show that there are trends toward a lower species richness and test concentration with greater elevation on the trunk and in lichens compared to mosses. There are considerable differences in community composition between sampling regions. Of all measured environmental variables only moisture content showed a significant relationship with testate amoeba community structure. Our data highlight how little is known about testate amoeba communities of this habitat and call for greater research efforts, particularly in less-studied regions and biomes. [ABSTRACT FROM AUTHOR]

The genus Korotnevella Goodkov, 1988 (Amoebozoa: Dactylopodida) comprises amoebae with a complex cell coat that include a layer of scales covering the entire cell surface. Until now no Korotnevella species were known to form cysts. Here we describe two new species of genus Korotnevella and provide a light- and electron-microscopic report of encystment in three species ( K. stella ( Schaeffer, 1926 ) Goodkov, 1988 , K. limbata n. sp. and K. heteracantha n. sp.) of this genus. Korotnevella limbata has two peculiar wide rims along the upper margin of basket scales forming two short spines at their junctions. The basket scales of K. heteracantha are very similar to those of K. bulla , but have a different spine length and a closed latticework basket with polygonal elements. All three studied species have similar cyst wall consisting of three layers. The outer layer contains scales of trophic stage; the middle one includes so called “cyst scales” with meshwork walls; and the inner one is composed of fibrillar material. Cyst structure of this sort appears to be unique for lobose amoebae and probably represents an autapomorphy for genus Korotnevella . [ABSTRACT FROM AUTHOR]

Bringing together more than 170 years of data, this study represents the first attempt to construct a species checklist and analyze the diversity and distribution of testate amoebae in Chile, a country that encompasses the southwestern region of South America, countless islands and part of the Antarctic. In Chile, known diversity includes 416 testate amoeba taxa (64 genera, 352 infrageneric taxa), 24 of which are here reported for the first time. Species−accumulation plots show that in Chile, the number of testate amoeba species reported has been continually increasing since the mid-19th century without leveling off. Testate amoebae have been recorded in 37 different habitats, though they are more diverse in peatlands and rainforest soils. Only 11% of species are widespread in continental Chile, while the remaining 89% of the species exhibit medium or short latitudinal distribution ranges. Also, species composition of insular Chile and the Chilean Antarctic territory is a depauperated subset of that found in continental Chile. Nearly, the 10% of the species reported here are endemic to Chile and many of them are distributed only within the so-called Chilean biodiversity hotspot (ca. 25° S-47° S). These findings are here thoroughly discussed in a biogeographical and evolutionary context. [ABSTRACT FROM AUTHOR]

This paper describes a new genus, Cunea n. g., of marine naked amoebae with two cryptic species, Cunea profundata and Cunea thuwala , isolated from distant localities in the ocean and different depths (Brazilian abyssal plain, Western Atlantic Ocean, depth >5 km and the Red Sea off the Saudi Arabian coast, depth ca. 58.7 m). Both species are very similar to each other in the set of light microscopic and ultrastructural characters and might be described as a single species, yet their genetic divergence based on 3 molecular markers (small-subunit ribosomal RNA, actin and cytochrome c oxidase subunit 1) corresponds to the level of variation typically observed between different morphospecies of Amoebozoa. In addition, the studied strains differ strongly in their temperature tolerance ranges, C . profundata isolated from the cold Atlantic deep-sea habitat being able to reproduce under lower temperatures than C . thuwala isolated from the warm Red Sea benthos. Molecular phylogenetic analysis based on SSU rRNA gene shows that the new genus robustly branches within the Dactylopodida, but forms an independent clade within this order that does not group with any of its known genera. [ABSTRACT FROM AUTHOR]

Amoebae able to form cytoplasmic networks or displaying a multiply branching morphology remain very poorly studied. We sequenced the small-subunit ribosomal RNA gene of 15 new amoeboid isolates, 14 of which are branching or network-forming amoebae (BNFA). Phylogenetic analyses showed that these isolates all group within the poorly-known and weakly-defined class Variosea (Amoebozoa). They are resolved into six lineages corresponding to distinct new morphotypes; we describe them as new genera Angulamoeba (type species Angulamoeba microcystivorans n. gen., n. sp.; and A. fungorum n. sp.), Arboramoeba (type species Arboramoeba reticulata n. gen., n. sp.), Darbyshirella (type species Darbyshirella terrestris n. gen., n. sp.), Dictyamoeba (type species Dictyamoeba vorax n. gen., n. sp.), Heliamoeba (type species Heliamoeba mirabilis n. gen., n. sp.), and Ischnamoeba (type species Ischnamoeba montana n. gen., n. sp.). We also isolated and sequenced four additional variosean strains, one belonging to Flamella , one related to Telaepolella tubasferens , and two members of the cavosteliid protosteloid lineage. We identified a further 104 putative variosean environmental clone sequences in GenBank, comprising up to 14 lineages that may prove to represent additional novel morphotypes. We show that BNFA are phylogenetically widespread in Variosea and morphologically very variable, both within and between lineages. [ABSTRACT FROM AUTHOR]

Legionella pneumophila is known as the causative agent of Legionnaires' disease and free-living amoebae (FLA) can serve as vehicles for legionellae. The aim of this study was to screen industrial waters for the occurrence of FLA and their co-occurrence with legionellae. A total of 201 water samples, including 129 cooling waters and 72 process waters, and 30 cooling lubricants were included in the study. Treated waters were screened periodically, pre and post treatment. Altogether, 72.6% of the water samples were positive for FLA, acanthamoebae being most prevalent (in 23.9% of the samples) followed by Vermamoeba vermiformis (19.4%). Only one cooling lubricant was positive (Acanthamoeba genotype T4). Legionella spp. were detected in 34.8% of the water samples and in 15% in high concentrations (>1000CFU/100ml). Altogether, 81.4% of the Legionella-positive samples were positive for FLA by standard methods. By applying a highly sensitive nested PCR to a representative set of random samples it was revealed that Legionella spp. always co-occurred with Acanthamoeba spp. Although the addition of disinfectants did influence amoebal density and diversity, treated waters showed no difference concerning FLA in the interphases of disinfection. It appears that FLA can re-colonize treated waters within a short period of time. [ABSTRACT FROM AUTHOR]

Arcellacea (testate lobose amoebae) are important lacustrine environmental indicators that have been used in paleoclimatic reconstructions, assessing the effectiveness of mine tailings pond reclamation projects and for studying the effects of land use change in rural, industrial and urban settings. Recognition of ecophenotypically significant infra-specific ‘strains’ within arcellacean assemblages has the potential to enhance the utility of the group in characterizing contemporary and paleoenvironments. We present a novel approach which employs statistical tools to investigate the environmental and taxonomic significance of proposed strains. We test this approach on two identified strains: Difflugia protaeiformis Lamarck strain ‘acuminata’ (DPA), characterized by fine grained agglutination, and Difflugia protaeiformis Lamarck strain ‘claviformis’ (DPC), characterized by coarse grained agglutination. Redundancy analysis indicated that both organisms are associated with similar environmental variables. No relationship was observed between substrate particle size and abundance of DPC, indicating that DPC has a size preference for xenosomes during test construction. Thus DPC should not be designated as a distinct strain but rather form a species complex with DPA. This study elucidates the need to justify the designation of strains based on their autecology in addition to morphological stability. [ABSTRACT FROM AUTHOR]

Abstract: Difflugia is a morphologically diverse genus of testate amoebae, which are common components of freshwater ecosystems. We observed a new morphotype similar to Difflugia tuberspinifera but without spine in four Xiamen reservoirs, Fujian Province, southeast China. We investigated its morphology and biometry using light and scanning electron microscopy. The linear discriminant analysis and principal component analysis of biometric characters revealed that the spiny and spineless forms of D. tuberspinifera differed only in the presence or absence of spine. Shell height, shell diameter, aperture diameter and collar height did not differ significantly between the two morphotypes. The number of conical spines varies from 0 to 8. However, the distribution of spine numbers showed two main modes at 0 (spineless form 45.1% of individuals) and 4–6 (38.9%), suggesting the possible existence of two genetically distinct lineages. Spines may have ecological and evolutionary significance. Our results suggested that the spiny and spineless morphotypes of D. tuberspinifera represent either a single variable taxon with different ecotypes or sibling species. Further morphological studies on clonal variations and molecular approaches are needed to clarify if the spineless morph represents an independent species or not. [Copyright &y& Elsevier]

Abstract: Two new species of the recently described genus Stenamoeba, named S. berchidia and S. sardiniensis were isolated from a single soil sample on Sardinia, Italy. Both share morphological features characteristic to Stenamoeba and form in phylogenetic analyses together with other Stenamoeba spp. a highly supported clade within the family Thecamoebidae. The ultrastructural investigation of Stenamoeba sardiniensis revealed the presence of cytoplasmic microtubule-organizing centers (MTOCs), located close to one of several dictyosomes found inside the cell. This is the first report of cytoplasmic MTOCs among Thecamoebidae. The presence of MTOCs is now shown in five of nine orders comprising the class Discosea and potentially could be a phylogenetic marker in this group. We re-isolated Stenamoeba limacina from German soils. This strain shows a similar morphology and an almost complete SSU rDNA sequence identity with the type strain of S. limacina originating from gills of fishes, collected in Czech Republic. [Copyright &y& Elsevier]

Endosymbiosis is a central and much studied process in the evolution of eukaryotes. While plastid evolution in eukaryotic algae has been extensively studied, much less is known about the evolution of mixotrophy in amoeboid protists, which has been found in three of the five super groups of Eukaryotes. We identified the green endosymbionts in four obligate mixotrophic testate amoeba species belonging to three major eukaryotic clades, Hyalosphenia papilio and Heleopera sphagni (Amoebozoa: Arcellinida), Placocista spinosa (Rhizaria: Euglyphida), and Archerella flavum (Stramenopiles: Labyrinthulomycetes) based on rbcL (ribulose-1,5-diphosphate carboxylase/oxygenase large subunit) gene sequences. We further investigated whether there were different phylotypes of algal endosymbionts within single H. papilio cells and the degree of host-symbiont specificity by amplifying two genes: COI (mitochondrial cytochrome oxydase subunit 1) from the testate amoeba host, and rbcL from the endosymbiont. Results show that all studied endosymbionts belong to genus Chlorella sensu stricto, closely related to Paramecium bursaria Chlorella symbionts, some lichen symbionts and also several free-living algae. Most rbcL gene sequences derived from symbionts from all testate amoeba species were almost identical (at most 3 silent nucleotides difference out of 780bp) and were assigned to a new Trebouxiophyceae taxon we named TACS (Testate Amoeba Chlorella Symbionts). This “one alga fits all mixotrophic testate amoeba” pattern suggests that photosynthetic symbionts have pre-adaptations to endosymbiosis and colonise diverse hosts from a free-living stage. [Copyright &y& Elsevier]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Legionella oakridgensis is able to cause Legionnaires’ disease, but is less virulent compared to L. pneumophila strains and very rarely associated with human disease. L. oakridgensis is the only species of the family legionellae which is able to grow on media without additional cysteine. In contrast to earlier publications, we found that L. oakridgensis is able to multiply in amoebae. We sequenced the genome of L. oakridgensis type strain OR-10 (ATCC 33761). The genome is smaller than the other yet sequenced Legionella genomes and has a higher G+C-content of 40.9%. L. oakridgensis lacks a flagellum and it also lacks all genes of the flagellar regulon except of the alternative sigma-28 factor FliA and the anti-sigma-28 factor FlgM. Genes encoding structural components of type I, type II, type IV Lvh and type IV Dot/Icm, Sec- and Tat-secretion systems could be identified. Only a limited set of Dot/Icm effector proteins have been recognized within the genome sequence of L. oakridgensis. Like in L. pneumophila strains, various proteins with eukaryotic motifs and eukaryote-like proteins were detected. We could demonstrate that the Dot/Icm system is essential for intracellular replication of L. oakridgensis. Furthermore, we identified new putative virulence factors of Legionella. [Copyright &y& Elsevier]

Euglyphid testate amoebae are a highly conspicuous group of Cercozoa whose systematics is based mainly on the shape and ultrastructure of the shell. However, only a couple of species have been studied with molecular methods. As a consequence, there are still some genera whose classification remains uncertain. Amongst those are Sphenoderia and Trachelocorythion, two genera with diverging ecological requirements that share a collar composed of small scales around the aperture. We demonstrate here with a molecular and morphological approach that they are closely related, and propose a new family, Sphenoderiidae fam. nov. to group these species. Some species share almost similar morphology in spite of being genetically distantly related (Sphenoderia minuta and S. pseudominuta sp. nov.), underlining the importance of combining ultrastructural and morphological data when describing new species of protists. In addition, we describe here Sphenoderia valdiviana sp. nov., a new species isolated from Southern Chile temperate rainforests. [Copyright &y& Elsevier]

In freshwater ecosystems a vast diversity of elusive protists exists that specifically feed on microalgae. Due to difficulties in isolation and long-term maintenance, most of these are still poorly known. In this study stable, bacteria-free cultures of several limnetic, algivorous amoeboflagellates were investigated by light microscopy and molecular phylogenetic analyses. All strains represent naked, biflagellate cells, either occurring as rigid flagellates or as surface-attached amoebae. They perforate cell walls of certain Zygnematophyceae and Chlorophyceae (Viridiplantae) and phagocytose algal cell contents. Time-lapse microscopy revealed the feeding behaviour, locomotional processes and life histories of the amoeboflagellates. Clear differences in cell morphology and food range specificity led to the description of two new, monotypic genera Orciraptor and Viridiraptor, which occupy similar, but distinct ecological niches in aquatic ecosystems as ‘necrophytophagous’ and ‘parasitoid’ protists, respectively. Molecular phylogenetic analyses based on 18S rDNA sequence data demonstrated that Orciraptor and Viridiraptor belonged to ‘clade X’ within the order Glissomonadida (Cercozoa, Rhizaria). In conclusion, we established the phenotypic identity of a clade, which until now was exclusively known from environmental sequences, and erect the new family Viridiraptoridae for ‘clade X’. Its algivorous members are compared with other glissomonads and nomenclatural, methodological and ecological aspects of these novel ‘raptorial’ amoeboflagellates are discussed. [Copyright &y& Elsevier]

Abstract: Breviata anathema is an anaerobic amoeboid flagellate that does not branch within any established ‘supergroup’. Molecular phylogenies suggest affinities to Amoebozoa, Opisthokonta, or apusomonads. Here we describe its flagellar apparatus ultrastructure. Breviata has two basal bodies. The flagellated anterior basal body (AB) is associated with a fan of ∼18 microtubules and a short singlet microtubular root. Three microtubular roots associate with the posterior basal body. One, the right root (RR), is initially a triplet that splits into two parts. The other two are singlets: the left root (LR), and the middle root (MR), which arises on the posterior side of the basal body. The MR, LR and smaller part of RR support the left ventral side of the cell, while the larger part of RR runs down the right. Outer dynein arms were not observed on the flagellar axoneme. The mitochondrion-like organelle sometimes contains some tubular cristae. The posterior flagellar apparatus resembles that of several eukaryotic lineages, particularly apusomonads, ancyromonads, excavates, and myxogastrid amoebozoans. This comparison suggests that the complex flagellar apparatus of myxogastrids is actually plesiomorphic within Amoebozoa. The widely distributed splitting right root and posterior singlet (MR in Breviata) may be plesiomorphies in many eukaryotic lineages, and thus could be features of the last eukaryotic common ancestor. [Copyright &y& Elsevier]

Abstract: The occurrence of ∑HCHs, ∑DDTs, protozoa abundance and their community structure in surface soils of orchards, vegetable lands, and barren lands in northern west outskirts of Beijing were detected in order to investigate the protozoa responses to low dose organic chlorinated Pesticides (OCPs) after long-term field-based exposure. Significant differences in total concentrations of HCHs and DDTs were found among the three general groups ranking in decreasing order of concentration from orchard>vegetable lands >barren lands. Ciliate was the rare group in surface soils of all the sampling groups. The abundance of flagellate, ciliate, and amoebae in vegetable soils were significantly higher than those in orchard soils. The abundance of all the taxa of protozoa was strongly negative correlated with the residue level of ∑HCHs and ∑DDTs (P<0.05) in agricultural soils. However, no negative correlation between the residue levels of OCPs and protozoa abundance was shown in both the orchard and the barren soils. This field study demonstrated a considerable long-term impact of the OCPs residue on the abundance of protozoa in soils, and that the abundance of soil protozoa was much more influenced by land use type in association with different soil properties. [Copyright &y& Elsevier]

The archamoebae form a small clade of anaerobic/microaerophilic flagellates or amoebae, comprising the pelobionts (mastigamoebids and pelomyxids) and the entamoebae. It is a member of the eukaryotic supergroup Amoebozoa. We examined 22 strains of 13 species of Mastigamoeba, Pelomyxa and Rhizomastix by light-microscopy and determined their SSU rRNA gene sequences. The SSU rRNA gene sequences of Pelomyxa palustris and Mastigella commutans in GenBank are shown to belong to P. stagnalis and Mastigamoeba punctachora, respectively. Five new species of free-living archamoebae are described: Mastigamoeba abducta, M. errans, M. guttula, M. lenta, and Rhizomastix libera spp. nov. A species of Mastigamoeba possibly living endosymbiotically in Pelomyxa was identified. Rhizomastix libera, the first known free-living member of that genus, is shown to be an archamoeba. R. libera possesses an ultrastructure unique within archamoebae: a rhizostyle formed from a modified microtubular cone and a flagellum with vanes. While many nominal species of pelobionts are extremely hard to distinguish by light microscopy, transient pseudopodial characters are worthy of further investigation as taxonomic markers. [Copyright &y& Elsevier]

Tubulinea is a phylogenetically stable higher-level taxon within Amoebozoa, morphologically characterized by monoaxially streaming and cylindrical pseudopods. Contemporary phylogenetic reconstructions have largely relied on SSU rDNA, and to a lesser extent, on actin genes to reveal the relationships among these organisms. Additionally, the test (shell) forming Arcellinida, one of the most species-rich amoebozoan groups, is nested within Tubulinea and suffers from substantial under-sampling of taxa. Here, we increase taxonomic and gene sampling within the Tubulinea, characterizing molecular data for 22 taxa and six genes (SSU rDNA, actin, α- and β-tubulin, elongation factor 2 and the 14-3-3 regulatory protein). We perform concatenated phylogenetic analyses using these genes as well as approximately unbiased tests to assess evolutionary relationships within the Tubulinea. We confirm the monophyly of Tubulinea and four of the six included lineages (Echinamoeboidea, Leptomyxida, Amoebida and Poseidonida). Arcellinida and Hartmanellidae, the remaining lineages, are not monophyletic in our reconstructions, although statistical testing does not allow rejection of either group. We further investigate more fine-grained morphological evolution of previously defined groups, concluding that relationships within Arcellinida are more consistent with general test and aperture shape than with test composition. We also discuss the implications of this phylogeny for interpretations of the Precambrian fossil record of testate amoebae. [Copyright &y& Elsevier]

Abstract: Shifts in community composition of soil protozoa in response to climate change may substantially influence microbial activity and thereby decomposition processes. However, effects of climate and vegetation on soil protozoa remain poorly understood. We studied the distribution of soil testate amoebae in herbaceous and shrubby vegetation along an altitudinal gradient (from below the treeline at 500m to the mid-alpine region at 900m a.s.l.) in subarctic tundra. To explain patterns in abundance, species diversity and assemblage composition of testate amoebae, a data set of microclimate and soil chemical characteristics was collected. Both elevation and vegetation influenced the assemblage composition of testate amoebae. The variation was regulated by interactive effects of summer soil moisture, winter soil temperature, soil pH and nitrate ion concentrations. Besides, soil moisture regulated non-linear patterns in species richness across the gradient. This is the first study showing the effects of winter soil temperatures on species composition of soil protozoa. The effects could be explained by specific adaptations of testate amoebae such as frost-resistant cysts allowing them to survive low winter temperatures. We conclude that the microclimate and soil chemical characteristics are the main drivers of changes in protozoan assemblage composition in response to elevation and vegetation. [Copyright &y& Elsevier]

Abstract: Species identification by means of morphology is often problematic in protists. Nebela tincta–collaris–bohemica (Arcellinida) is a species complex of small to medium-sized (ca.100μm) testate amoebae common in peat bogs and forest soils. The taxonomic validity of characters used to define species within this group is debated and causes confusion in studies of biogeography, and applications in palaeoecology. We examined the relationship between morphological and genetic diversity within this species complex by combined analyses of light microscopy imaging and Cytochrome Oxidase Subunit 1(COI) sequences obtained from the same individual amoeba cells. Our goals were (1) to clarify the taxonomy and the phylogenetic relationships within this group, and (2) to evaluate if individual genotypes corresponded to specific morphotypes and the extent of phenotypic plasticity. We show here that small variations in test morphology that have been often overlooked by traditional taxonomy correspond to distinct haplotypes. We therefore revise the taxonomy of the group. We redefine Nebela tincta (Leidy) Kosakyan et Lara and N. collaris (Ehrenberg 1848) Kosakyan et Gomaa, change N. tincta var. rotunda Penard to N. rotunda (Penard 1890), describe three new species: N. guttata n. sp. Kosakyan et Lara, N. pechorensis n. sp. Kosakyan et Mitchell, and N. aliciae n. sp. Mitchell et Lara. [Copyright &y& Elsevier]

Investigation of soil amoebae in 11 cooling towers allowed us to isolate a major unknown small-sized amoeba population (SZA). However, SZA did not appear to be specific to cooling tower ecosystems since they are also a major amoeba population found in muds isolated from different points of a water treatment plant. The SSU-rDNA sequences from SZA strains did not match any known database sequences, suggesting that SZA constitutes a new amoeba taxon. We isolated and further described one of the SZA that we named Micriamoeba tesseris. The phylogenetic analyses showed that Micriamoeba tesseris belongs to the Amebozoa and branched together with genus Echinamoeba + Vermamoeba vermiformis. Phylogenetic analyses within the Micriamoeba group distinguished different subgroups of Micriamoeba strains according to their origin, i.e. cooling tower or mud. Although Micriamoeba are able to feed on viable E. coli cells, they do not uptake virulent Legionella pneumophila strains, thus enabling them to avoid infection by Legionella. Consequently, Micriamoeba is not directly involved in L. pneumophila multiplication. However, an indirect role of Micriamoeba in Legionella risk is discussed. [ABSTRACT FROM AUTHOR]

Testate amoebae represent a crucial component of soil microfauna and have been studied extensively in ombrotrophic peatlands. However, little is known about their ecology in moorlands which are important habitats in terms of biodiversity and carbon storage potential. Moorlands are under threat from a range of factors such as drainage, burning, over grazing, pollution and climate change. In this study we investigate testate amoebae communities within three zones of a UK moorland characterised by contrasting fire histories, and use these data to examine the potential of testate amoebae as environmental bioindicators in moorlands. Although several factors control testate amoebae communities in moorlands, it is clear that there are marked differences in testate amoebae communities between the zones which primarily relate to hydrological status, influenced by fire regime. The taxon Hyalosphenia subflava is a clear indicator of severe disturbance as it was found to be abundant in mosses which colonised a hydrophobic peat surface following a severe wild-fire event. Testate amoebae have much potential for ecosystem monitoring of moorlands which can inform sustainable land management practices. [ABSTRACT FROM AUTHOR]

We isolated and cultivated 31 strains of free-living heterolobosean flagellates and amoebae from freshwater, brackish, and marine sediments with low concentrations of oxygen. Phylogenetic analysis of small subunit (SSU) rDNA showed that the strains constitute a single clade, the Psalteriomonadidae. According to combined light-microscopic morphology plus molecular phylogeny, our isolates belong to seven species and five genera, from which three species and two genera are new. In addition, previously described anaerobic species Percolomonas descissus and Vahlkampfia anaerobica are transferred to the Psalteriomonadidae. We identified a flagellate stage of Monopylocystis visvesvarai which was reported to produce only amoebae. Two environmental sequences previously obtained from acidic environments belong to the Psalteriomonadidae as well, suggesting a broad ecological importance of the Psalteriomonadidae. The ultrastructure of two psalteriomonadid species was also studied. Unifying features of the Psalteriomonadidae are acristate mitochondrial derivates, flagellates with a ventral groove and four flagella, and a harp-like structure in the mastigont. A new overall classification of the Psalteriomonadidae is proposed. Our data show that the Psalteriomonadidae are much more diverse than previously thought and constitute the main anaerobic lineage within the Heterolobosea. [ABSTRACT FROM AUTHOR]

Population dynamics and feeding habits of the testate amoebae Nebela tincta and Hyalosphenia papilio were studied along a short “fen” to “bog” gradient in a Sphagnum-dominated mire (Jura, France). Samples were collected in living “top segments” (0-3cm) and early declining “bottom segments” (3-6cm) of Sphagnum fallax peat. Observations of digestive vacuole content and stable isotope analyses (13C and 15N) were used to establish the feeding behavior of both testate amoeba species. Owing to their vertical distribution, the feeding habit of H. papilio was described from top segments, and that of N. tincta from bottom segments. Among identified food sources, those most frequently ingested by N. tincta were spores and mycelia of fungi (55%), microalgae (25%) and cyanobacteria (8.5%). For H. papilio, the most frequently ingested prey were ciliates (55%) and microalgae (35%). Nonmetric Multidimensional Scaling analysis clearly demonstrated that the two species did not have the same feeding habit along the “fen-bog” gradient, and furthermore that a significant spatial split exists in the feeding behavior of H. papilio. Additionally, isotope analyses suggested that H. papilio and N. tincta did not have the same trophic position in the microbial food web, probably resulting from their different feeding strategies. [Copyright &y& Elsevier]

We used Cytochrome Oxidase Subunit 1 (COI) to assess the phylogenetic relationships and taxonomy of Nebela sensu stricto and similar taxa (Nebela group, Arcellinida) in order to clarify the taxonomic validity of morphological characters. The COI data not only successfully separated all studied morphospecies but also revealed the existence of several potential cryptic species. The taxonomic implications of the results are: (1) Genus Nebela is paraphyletic and will need to be split into at least two monophyletic assemblages when taxon sampling is further expanded. (2) Genus Quadrulella, one of the few arcellinid genera building its shell from self-secreted siliceous elements, and the mixotrophic Hyalosphenia papilio branch within the Nebela group in agreement with the general morphology of their shell and the presence of an organic rim around the aperture (synapomorphy for Hyalospheniidae). We thus synonymise Hyalospheniidae and Nebelidae. Hyalospheniidae takes precedence and now includes Hyalosphenia, Quadrulella (previously in the Lesquereusiidae) and all Nebelidae with the exception of Argynnia and Physochila. Leptochlamys is Arcellinida incertae sedis. We describe a new genus Padaungiella Lara et Todorov and a new species Nebela meisterfeldi n. sp. Heger et Mitchell and revise the taxonomic position (and rank) of several taxa. These results show that the traditional morphology-based taxonomy underestimates the diversity within the Nebela group, and that phylogenetic relationships are best inferred from shell shape rather than from the material used to build the shell. [Copyright &y& Elsevier]

Sphagnum-dwelling testate amoebae are widely used in paleoclimate reconstructions as a proxy for climate-induced changes in bogs. However, the sensitivity of proxies to seasonal climate components is an important issue when interpreting proxy records. Here, we studied the effects of summer warming, winter snow addition solely and winter snow addition together with spring warming on testate amoeba assemblages after eight years of experimental field climate manipulations. All manipulations were accomplished using open top chambers in a dry blanket bog located in the sub-Arctic (Abisko, Sweden). We estimated sensitivity of abundance, diversity and assemblage structure of living and empty shell assemblages of testate amoebae in the living and decaying layers of Sphagnum. Our results show that, in a sub-arctic climate, testate amoebae are more sensitive to climate changes in the growing season than in winter. Summer warming reduced species richness and shifted assemblage composition towards predominance of xerophilous species for the living and empty shell assemblages in both layers. The higher soil temperatures during the growing season also decreased abundance of empty shells in both layers hinting at a possible increase in their decomposition rates. Thus, although possible effects of climate changes on preservation of empty shells should always be taken into account, species diversity and structure of testate amoeba assemblages in dry subarctic bogs are sensitive proxies for climatic changes during the growing season. [Copyright &y& Elsevier]

Dictyostelid social amoebae are a large and ancient group of soil microbes with an unusual multicellular stage in their life cycle. Taxonomically, they belong to the eukaryotic supergroup Amoebozoa, the sister group to Opisthokonta (animals + fungi). Roughly half of the ∼150 known dictyostelid species were discovered during the last five years and probably many more remain to be found. The traditional classification system of Dictyostelia was completely overturned by cladistic analyses and molecular phylogenies of the past six years. As a result, it now appears that, instead of three major divisions there are eight, none of which correspond to traditional higher-level taxa. In addition to the widely studied Dictyostelium discoideum, there are now efforts to develop model organisms and complete genome sequences for each major group. Thus Dictyostelia is becoming an excellent model for both practical, medically related research and for studying basic principles in cell-cell communication and developmental evolution. In this review we summarize the latest information about their life cycle, taxonomy, evolutionary history, genome projects and practical importance. [Copyright &y& Elsevier]

Naegleria fowleri is the etiologic agent of primary amoebic meningoencephalitis (PAM), a rapidly fatal disease. Although PAM generally occurs after recreational exposure to contaminated water, two fatal cases of PAM were linked to a drinking water supply in Arizona. This study tested the ability of distribution system biofilms to be reservoirs for N. fowleri and other amoebae. When introduced to laboratory pipe loops, N. fowleri attached to biofilms and survived for five months. In two fullscale distribution systems, amoebic activity was detected in 67% of biofilm samples tested, regardless of chlorination. Amoebic activity occurred mostly in locations associated with stagnant water and high bacterial counts. Legionella was also found in 65% of biofilm samples. Although N. fowleri was never detected in field samples, the observed risk factors—high bacterial counts, amoebic activity, and the presence of Legionella in biofilms—suggest that N. fowleri could thrive in both systems if introduced. [ABSTRACT FROM AUTHOR]

The social amoebae (Dictyostelia) use quorum sensing-like communication systems to coordinate the periodic transition from uni- to multicellularity. The monophyletic descent of the Dictyostelia provides a unique opportunity to study the origin and adaptive evolution of such intercellular communication systems. We determined that the ability of aggregation-competent cells to respond to the intercellular messenger glorin occurred in the most ancient taxa of the Dictyostelia. We show using Illumina sequencing technology that glorin mediates rapid changes in gene expression at the transition from vegetative growth to aggregation. We conclude that peptide-based communication is the most ancient form of intercellular signaling in the evolution of multicellularity in the social amoebae, but has been repeatedly replaced by other communication systems during the monophyletic evolution of the social amoebae. Glorin communication has parallels with quorum sensing in that the molecule diffuses into the field, stimulates gene expression in receptive cells and coordinates a population-wide response. [Copyright &y& Elsevier]

Abstract: We studied a long time series of the dynamics in space and time of four species of Difflugia (thecamoebae) that co-exist in the pelagic plankton of Liuxihe Reservoir, an oligo-mesotrophic impoundment in southern China, during 8–9 months (“summer” form March to November), and retreat to the benthos during the rest of the year (“winter”). We discuss the reasons for the winter retreat, and suggest that predator evasion may be involved, although temperature-linked physiological effects (like the rate of gas bubble production) appear more probable. Clear diel vertical migration of Difflugia was not observed, but patchiness was common. We found no evident lake edge-effects in the spatial pattern either, but the abundances were strongly influenced by trophic conditions and increased by up to one order of magnitude in the upstream, eutrophic sections of the reservoir. [Copyright &y& Elsevier]

We describe three new orders of filosan Cercozoa, five new deep-branching genera, eight new species of Thaumatomonas, Reckertia, Spongomonas, Rhogostoma, Agitata, Neoheteromita and Paracercomonas, sequence their 18S rDNA, and construct 18S rDNA trees for 148 Cercozoa. Our phylogeny indicates that Filosa were ancestrally gliding flagellates; non-flagellate filose amoebae evolved from them five times independently. The new genera are more closely related to environmental DNA sequences than cultured organisms. Tremula longifila, a zooflagellate glider on both flagella (unlike other Cercozoa), is the most divergent filosan (Tremulida ord. n.). Micrometopion nutans is a eukaryote-eating gliding zooflagellate like Metopion and Metromonas. Minimassisteria diva is a widespread trimorphic marine amoeboflagellate granofilosan. Peregrinia clavideferens, a non-testate, scale-bearing, filose amoeba, branches deeply in Thaumatomonadida, which are probably sisters to Spongomonadida. Nudifila producta is a filose amoeboflagellate related to Clautriavia and Marimonadida (ord. n., e.g. Pseudopirsonia, Auranticordis). We substantially revise Imbricatea, now including Spongomonadida, and Thecofilosea to include Phaeodaria. Thecofilosea and Imbricatea and Thecofilosea are sisters, both arguably ancestrally rigid gliding flagellates with ventral pseudopod-emitting grooves. Scale-free Ovulinata parva is sister to Paulinella, so imbricate silica scales can be lost. Internal hollow silica skeletons evolved twice in Thecofilosea (Ebriida, Phaeodaria) or were multiply lost. Protaspa replaces preoccupied ‘Protaspis’. [ABSTRACT FROM AUTHOR]

Soil testate amoebae assemblages in a grassland area at Zackenberg (Northeast Greenland) were subjected to simulated climate-warming during the growing season using the Free-Air Temperature Increase technique. Samples were collected in upper (0 – 3cm) and deeper (3 – 6cm) soil horizons. Mean temperature elevations at 2.5 and 7.5 cm depth were 2.58 ± SD 1.11 and 2.13±SD 0.77°C, respectively, and did not differ significantly. Soil moisture in the top 11cm was not affected by the warming. During the manipulation, the densities of living amoebae and empty shells were higher in the experimental plots but only in the upper layer. Possibly, testate amoebae in the deeper layer were limited by other factors, suggesting that warming enhances the carrying capacity only in favourable conditions. Species richness, on the other hand, was only increased in the deeper horizon. Warming did not change the percentage of individuals belonging to small-sized species in any of the living assemblages, contrary to our expectation that those species would quickly increase their density. However, in the empty shell assemblages, the proportion of small-sized individuals in the experimental plots was higher in both layers, indicating a rapid, transient increase in small amoebae before the first sampling date. Changes in successional state of testate amoebae assemblages in response to future climate change might thus be ephemeral, whereas alterations in density and species richness might be more sustained. [ABSTRACT FROM AUTHOR]