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Due to frequent variations in environmental conditions, free-living amoebae adapt through differentiation into different states. Hence, favorable conditions enable the formation of a feeding and proliferative form named "Trophozoïte" whereas unfavorable situations drive differentiation into resting and resistant single forms such as cysts, spores, or multicellular structures. Transformation into cyst, named "encystment" or "encystation", is a common feature found in testate, naked, or flagellated free-living amoebae. Although much effort has been made to understand encystment, several blind spots are still present. This short opinion paper highlights some difficulties impeding a better understanding of encystment. [ABSTRACT FROM AUTHOR]

In Ukrainian water bodies, the genus Mayorella Schaeffer, 1926 is represented by ten species: Mayorella cantabrigiensis Page, 1983, Mayorella vespertilioides Page, 1983, Mayorella bigemma Schaeffer, 1918, Mayorella leidyi Bovee, 1970, Mayorella penardi Page, 1972, Mayorella viridis Leidy, 1874, Mayorella sp. (1), Mayorella sp. (2), Mayorella sp. (3), Mayorella sp. (4). The most widely distributed are M. cantabrigiensis, M. vespertilioides, Mayorella sp. (1), the least observed are M. leidyi, M. penardi, M. viridis, Mayorella sp. (4). The distribution of amoebae is influenced by abiotic environmental factors. [ABSTRACT FROM AUTHOR]

In Ukrainian water bodies, the genus Mayorella Schaeff er, 1926 is represented by ten species: Mayorella cantabrigiensis Page, 1983, Mayorella vespertilioides Page, 1983, Mayorella bigemma Schaeff er, 1918, Mayorella leidyi Bovee, 1970, Mayorella penardi Page, 1972, Mayorella viridis Leidy, 1874, Mayorella sp. (1), Mayorella sp. (2), Mayorella sp. (3), Mayorella sp. (4). Th e most widely distributed are M. cantabrigiensis, M. vespertilioides, Mayorella sp. (1), the least observed are M. leidyi, M. penardi, M. viridis, Mayorella sp. (4). Th e distribution of amoebae is influenced by abiotic environmental factors. [ABSTRACT FROM AUTHOR]

Waddlia chondrophila is an intracellular bacterium phylogenetically related to the well-studied human and animal pathogens of the Chlamydiaceae family. In the last decade, W. chondrophila was convincingly demonstrated to be associated with adverse pregnancy outcomes in humans and abortions in animals. All members of the phylum Chlamydiae possess a Type Three Secretion System that they use for delivering virulence proteins into the host cell cytosol to modulate their environment and create optimal conditions to complete their life cycle. To identify W. chondrophila virulence proteins, we used an original screening approach that combines a cosmid library with an assay monitoring resistance to predation by phagocytic amoebae. This technique combined with bioinformatic data allowed the identification of 28 candidate virulence proteins, including Wimp1, the first identified inclusion membrane protein of W. chondrophila. [ABSTRACT FROM AUTHOR]

The American Type Culture Collection (ATCC) PRA‐29 isolate has a publicly available transcriptome, which has led to its inclusion in recent phylogenomic analyses. The ATCC PRA‐29 isolate was originally identified and deposited as "Pessonella sp." This taxon branches robustly within the recently discovered clade Cutosea, very distantly related to the clade in which the genus Pessonella is believed to branch based on morphological data. Using detailed light and electron microscopy, we studied the morphology and ultrastructure of ATCC PRA‐29 as well as other cutosean amoebae to better elucidate the morphological affinity of ATCC PRA‐29 to other amoebozoans. Here, we show that ATCC PRA‐29 was misidentified by the original depositor as Pessonella and name it Armaparvus languidus n. gen. n. sp. We show that a cell coat of microscales separated from the cell membrane is a unique trait found in all known cutosean amoebae. As Cutosea represents a clade at the deepest bifurcation in the amoebozoan group Evosea and because this clade is currently taxon‐poor, but likely represents a major understudied group it will be important to isolate and describe more cutosean amoebae in the future. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the occurrence of free-living amoebae (FLA) in Peninsular Malaysia and to compare different methodologies to detect them from water samples. Water samples were collected from tap water, recreational places, water dispensers, filtered water, etc. and tested for FLA using both cultivation and polymerase chain reaction (PCR) via plating assays and centrifugation methods. Amoebae DNA was extracted using Instagene matrix and PCR was performed using genus-specific primers. Of 250 samples, 142 (56.8%) samples were positive for presence of amoebae, while 108 (43.2%) were negative. Recreational water showed higher prevalence of amoebae than tap water. PCR for the plating assays revealed the presence of Acanthamoeba in 91 (64%) samples and Naegleria in 99 (70%) of samples analysed. All samples tested were negative for B. mandrillaris. In contrast, the centrifugation method was less effective in detecting amoebae as only one sample revealed the presence of Acanthamoeba and 52 (29%) samples were positive for Naegleria. PCR assays were specific and sensitive, detecting as few as 10 cells. These findings show the vast distribution and presence of FLA in all 11 states of Peninsular Malaysia. Further studies could determine the possible presence of pathogenic species and strains of free-living amoebae in public water supplies in Malaysia. [ABSTRACT FROM AUTHOR]

The construction of reservoirs impacts upon freshwater ecosystems, since it changes the hydrodynamics of the entire system upstream and downstream of the dam due to flow control and changes in environmental conditions. We analyzed the temporal variation in the abundance of exogenous testate amoebae related to the suspended inorganic material in Neotropical floodplain lakes, downstream of a series of dams. Sampling was carried out between 2000 and 2012 in six lakes in the upper Paraná River floodplain. The temporal variation in the abundance of the testate amoeba community was analyzed using the Threshold Indicator Taxa Analysis. Cucurbitella crateriformis, Protocucurbitella coroniformes, and C dentata f. quinquilobata had reduced population growth in higher concentrations of suspended inorganic material. On the other hand, Difflugia lobostoma, Centropyxis ecornis, and Difflugia pseudogramen populations increased under these conditions. These results showed that an increased flow of water could favor the growth of some populations due to the greater exchange of material between the lakes and the floodplain. The positive or negative responses could show better adaptation of the testate amoeba species to the planktonic environment. Furthermore, these results also highlighted the bioindicator role of these protozoa in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

The 14th International Workshops on Opportunistic Protists (IWOP‐14) was held August 10–12, 2017 in Cincinnati, OH, USA. The IWOP meetings focus on opportunistic protists (OIs); for example, free‐living amoebae, Pneumocystis spp., Cryptosporidium spp., Toxoplasma, the Microsporidia, and kinetoplastid flagellates. The highlights of Pneumocystis spp. research included the reports of primary homothallism for mating; a potential requirement for sexual replication in its life cycle; a new antigen on the surface of small asci; roles for CLRs, Dectin‐1, and Mincle in host responses; and identification of MSG families and mechanisms used for surface variation. Studies of Cryptosporidia spp. included comparative genomics, a new cryopreservation method; the role of mucin in attachment and invasion, and epidemiological surveys illustrating species diversity in animals. One of the five identified proteins in the polar tube of Microsporidia, PTP4, was shown to play a role in host infection. Zebrafish were used as a low cost vertebrate animal model for an evaluation of potential anti‐toxoplasma drugs. Folk medicine compounds with anti‐toxoplasma activity were presented, and reports on the chronic toxoplasma infection provided evidence for increased tractability for the study of this difficult life cycle stage. Escape from the parasitophorus vacuole and cell cycle regulation were the topics of the study in the acute phase. [ABSTRACT FROM AUTHOR]

Sex and reproduction are often treated as a single phenomenon in animals and plants, as in these organisms reproduction implies mixis and meiosis. In contrast, sex and reproduction are independent biological phenomena that may or may not be linked in the majority of other eukaryotes. Current evidence supports a eukaryotic ancestor bearing a mating type system and meiosis, which is a process exclusive to eukaryotes. Even though sex is ancestral, the literature regarding life cycles of amoeboid lineages depicts them as asexual organisms. Why would loss of sex be common in amoebae, if it is rarely lost, if ever, in plants and animals, as well as in fungi? One way to approach the question of meiosis in the "asexuals" is to evaluate the patterns of occurrence of genes for the proteins involved in syngamy and meiosis. We have applied a comparative genomic approach to study the occurrence of the machinery for plasmogamy, karyogamy, and meiosis in Amoebozoa, a major amoeboid supergroup. Our results support a putative occurrence of syngamy and meiotic processes in all major amoebozoan lineages. We conclude that most amoebozoans may perform mixis, recombination, and ploidy reduction through canonical meiotic processes. The present evidence indicates the possibility of sexual cycles in many lineages traditionally held as asexual. [ABSTRACT FROM AUTHOR]

Achromatium is the largest freshwater bacterium known to date and easily recognised by conspicuous calcite bodies filling the cell volume. Members of this genus are highly abundant in diverse aquatic sediments and may account for up to 90% of the bacterial biovolume in the oxic-anoxic interfaces. The high abundance implies that Achromatium is either rapidly growing or hardly prone to predation. As Achromatium is still uncultivated and does not appear to grow fast, one could assume that the cells might escape predation by their unusual shape and composition. However, we observed various members of the meiofauna grazing or parasitizing on Achromatium. By microphotography, we documented amoebae, ciliates, oligochetes and plathelminthes having Achromatium cells ingested. Some Achromatium cells harboured structures resembling sporangia of parasitic fungi (chytrids) that could be stained with the chitin-specific dye Calcofluor White. Many Achromatia carried prokaryotic epibionts in the slime layer surrounding the cells. Their regular distribution over the cell might indicate that they are commensalistic rather than harming their hosts. In conclusion, we report on various interactions of Achromatium with the sediment community and show that although Achromatium cells are a crispy diet, full of calcite bodies, predators do not spare them. [ABSTRACT FROM AUTHOR]

Abstract: Class Ascetosporea (Rhizaria; Endomyxa) comprises many parasites of invertebrates. Within this group, recent group‐specific environmental DNA (eDNA) studies have contributed to the establishment of the new order Mikrocytida, a new phylogeny and characterization of Paramyxida, and illuminated the diversity and distribution of haplosporidians. Here, we use general and lineage‐specific PCR primers to investigate the phylogenetic “gap” between haplosporidians and their closest known free‐living relatives, the testate amoeba Gromia and reticulate amoeba Filoreta. Within this gap are Paradinium spp. parasites of copepods, which we show to be highly diverse and widely distributed in planktonic and benthic samples. We reveal a robustly supported radiation of parasites, ENDO‐3, comprised of Paradinium and three further clades (ENDO‐3a, ENDO‐3b and SPP). A further environmental group, ENDO‐2, perhaps comprising several clades, branches between this radiation and the free‐living amoebae. Early diverging haplosporidians were also amplified, often associated with bivalves or deep‐sea samples. The general primer approach amplified an overlapping set of novel lineages within ENDO‐3 and Haplosporida, whereas the group‐specific primer strategy, targeted to amplify from the earliest known divergent haplosporidians to Gromia, generated greater sequence diversity across part of this phylogenetic range. [ABSTRACT FROM AUTHOR]

Background: Free-living amoebae (FLA) are voracious feeders, consuming bacteria and other microbes during colonization of the phytobiome. FLA are also known to secrete bacteriocidal or bacteriostatic compounds into their growth environment. Methodology and principal findings: Here, we explore the impacts of co-cultivation of five FLA species, including Acanthamoeba castellanii, A. lenticulata, A. polyphaga, Dictyostelium discoideum and Vermamoeba vermiformis, on survival of two devastating bacterial pathogens of rice, Xanthomonas oryzae pathovars (pv.) oryzae and oryzicola. In co-cultivation assays, the five FLA species were either bacteriostatic or bactericidal to X. oryzae pv. oryzae and X. oryzae pv. oryzicola. Despite these effects, bacteria were rarely detected inside amoebal cells. Furthermore, amoebae did not disrupt X. oryzae biofilms. The bactericidal effects persisted when bacteria were added to a cell-free supernatant from amoebal cultures, suggesting some amoebae produce an extracellular bactericidal compound. Conclusions/Significance: This work establishes novel, basal dynamics between important plant pathogenic bacteria and diverse amoebae, and lays the framework for future mechanistic studies. [ABSTRACT FROM AUTHOR]

Arcellinida (lobose testate amoebae) preserve well in lake sediments and have shown great potential as palaeolimnological indicators, but a limited understanding of their ecology prevents more in-depth interpretations of both contemporary and fossil assemblages. Loch Leven, Scotland, has a well-documented history of nutrient-enrichment and associated lake biological change, creating a temporal gradient along which testate amoeba ecology can be investigated. Plant macrofossil data from a dated sediment core (LEVE14) indicate that a transition from oligo-mesotrophic to eutrophic conditions occurred over at least the last 200 years, enabling direct comparisons to be drawn with fossil testate amoeba assemblages from the same core. Cluster analysis and principal components analysis show that testate amoebae and macrophytes responded synchronously to an early phase of nutrient-enrichment after ca. AD 1200, and to anthropogenic water-level lowering and further enrichment after ca. AD 1830. The results of indicator species analysis (IndVal) support the suggestion inferred previously that Cucurbitella tricuspis is an indicator of nutrient-enrichment, while the association of some less abundant taxa, specifically Difflugia amphora and Mediolus corona, with eutrophic environments is also corroborated. Overall, the testate amoeba assemblage response appears to reflect a complex interaction of factors which were ultimately driven by eutrophication. These include variations in microhabitat associated with changing plant structure and sedimentary conditions influenced by macrophyte community succession. In particular, a shift from an oligo-mesotrophic macrophyte assemblage composed of isoetid plants to one dominated by Potamogeton spp. and dense stands of Characeae is suggested to influence the relative proportions of sediment dwelling and plant-associated testate amoebae. The results highlight the utility of testate amoebae as benthic indicators of lake nutrient-enrichment and demonstrate the value of using multi-proxy palaeolimnological data to refine the ecology of lesser-studied palaeoecological groups. [ABSTRACT FROM AUTHOR]

As most ecosystems, peatlands have been heavily exploited for different human purposes. For example, in Finland the majority is under forestry, agriculture or peat mining use. Peatlands play an important role in carbon storage, water cycle, and are a unique habitat for rare organisms. Such properties highlight their environmental importance and the need for their restoration. To monitor the success of peatland restoration sensitive indicators are needed. Here we test whether testate amoebae can be used as a reliable bioindicator for assessing peatland condition. To qualify as reliable indicators, responses in testate amoebae community structure to ecological changes must be stronger than random spatial and temporal variation. In this study, we simultaneously assessed differences between the effects of seasonality, intermediate scale spatial variation and land uses on living testate amoebae assemblages in natural, forested and restored peatlands. We expected the effects of seasonality on testate amoebae communities to be less pronounced than those of land use and within site variation. On average, natural sites harboured the highest richness and density, while the lowest numbers were found at forestry sites. Despite small changes observed in taxa dominance and differences in TA community structure between seasons and years at some sites, spatial heterogeneity, temperature, pH, nor water table depth seemed to significantly affect testate amoebae communities. Instead, observed differences were related to type of land use, which explained 75% of the community variation. Our results showed that testate amoebae community monitoring is a useful tool to evaluate impacts of human land use on boreal peatlands. [ABSTRACT FROM AUTHOR]

Abstract: Two amoeboid organisms of the genera Sappinia Dangeard, 1896 and Rosculus Hawes, 1963 were identified in a sample containing king penguin guano. This sample, collected in the Subantarctic, enlarges the list of fecal habitats known for the presence of coprophilic amoebae. The two organisms were co‐isolated and subcultured for over 6 mo, with continuous efforts being invested to separate each one from the mixed culture. In the mixed culture, Rosculus cells were fast growing, tolerated changes in culturing conditions, formed cysts, and evidently were attracted by Sappinia trophozoites. The separation of the Rosculus strain was accomplished, whereas the Sappinia strain remained intermixed with inseparable Rosculus cells. Sappinia cell populations were sensitive to changes in culturing conditions; they improved with reduction of Rosculus cells in the mixed culture. Thick‐walled cysts, reportedly formed by Sappinia species, were not seen. The ultrastructure of both organisms was congruent with the currently accepted generic characteristics; however, some details were remarkable at the species level. Combined with the results of phylogenetic analyses, our findings indicate that the ultrastructure of the glycocalyx and the presence/absence of the Golgi apparatus in differential diagnoses of Sappinia species require a critical re‐evaluation. [ABSTRACT FROM AUTHOR]

Testate amoebae have proved a useful group of species to understand the biogeography of larger microorganisms. The Arctic has attracted particular interest in such studies but there are large geographic gaps in current knowledge. Here we present what we believe is the first ever study of testate amoebae from the Novaya Zemlya archipelago in Arctic Russia. We investigated testate amoebae from the northernmost island of Novaya Zemlya proper and two smaller islands to the south: Dolgii Island and Matveev Island. We found that testate amoebae were present and active even in the extreme physical environment of northern Novaya Zemlya. Further south in the tundra zone of Dolgii and Matveev islands, testate amoebae were notably abundant and diverse. There were distinct differences in assemblage between all three islands and particularly between Novaya Zemlya and the two more southerly islands. The assemblage of Novaya Zemlya was distinctive with a surprising abundance of larger taxa. Comparisons to previous data suggest that the testate amoeba assemblages of these islands may show more affinity to those further west in Greenland and Svalbard than those further east in Siberia. Results highlight the limited knowledge of the abundance and diversity of these functionally significant protists in large areas of the globe. [ABSTRACT FROM AUTHOR]

Investigating microbial interactions from an ecological perspective is a particularly fruitful approach to unveil both new chemistry and bioactivity. Microbial predator-prey interactions in particular rely on natural products as signal or defense molecules. In this context, we identified a grazing-resistant Pseudomonas strain, isolated from the bacterivorous amoeba Dictyostelium discoideum. Genome analysis of this bacterium revealed the presence of two biosynthetic gene clusters that were found adjacent to each other on a contiguous stretch of the bacterial genome. Although one cluster codes for the polyketide synthase producing the known antibiotic mupirocin, the other cluster encodes a nonribosomal peptide synthetase leading to the unreported cyclic lipopeptide jessenipeptin. We describe its complete structure elucidation, as well as its synergistic activity against methicillin-resistant Staphylococcus aureus, when in combination with mupirocin. Both biosynthetic gene clusters are regulated by quorum-sensing systems, with 3-oxo-decanoyl homoserine lactone (3-oxo-C10-AHL) and hexanoyl homoserine lactone (C6-AHL) being the respective signal molecules. This study highlights the regulation, richness, and complex interplay of bacterial natural products that emerge in the context of microbial competition. [ABSTRACT FROM AUTHOR]

The present study was aimed at designing and optimizing a rotating disk reactor simulating high hydrodynamic shear rates (γ), which are representative of cooling circuits. The characteristics of the hydrodynamic conditions in the reactor and the complex approach used to engineer it are described. A 60 l tank was filled with freshwater containing free-living amoebae (FLA) and bacteria. Adhesion of the bacteria and formation of a biofilm on the stainless steel coupons were observed. FLA were able to establish in these biofilms under γ as high as 85,000 s−1. Several physical mechanisms (convection, diffusion, sedimentation) could explain the accumulation of amoeboid cells on surfaces, but further research is required to fully understand and model the fine mechanisms governing such transport under γ similar to those encountered in the industrial environment. This technological advance may enable research into these topics. [ABSTRACT FROM AUTHOR]

In order to clearly understand the response of raised mires to past climate change, it is important to consider the full range of drivers and responses of these ecohydrological archives. To this end, a high-resolution ecohydrological record from Littleton Bog, Co. Tipperary, Ireland, was generated utilizing a combination of plant macrofossils, testate amoebae and humification analysis. Chronological control for this record was provided by a Bayesian age–depth model based on AMS radiocarbon dates. Testate amoebae–derived reconstructed peatland water tables indicate a series of sudden shifts to dry bog surface conditions at c. 3140, c. 2510 and c. 1540 cal. BP. These events display a distinctive palaeoecological signal and chronological tempo that is best explained as a result of a series of bog burst events and which seem inconsistent with other explanations. The chronological correspondence between the bog bursts at Littleton and a set of similar events at Derryville Bog, c. 5 km to the north, is noted, as is the broad correspondence of these events with wet shifts indicated in regional peatland water table compilations from Britain and Ireland. A range of possible driving mechanisms for these events is proposed, including anthropogenic disturbance of the bog surface, non-linear response to climate forcing, internal bog dynamics, vegetation succession or a combination of factors. We illustrate the need for further multi-proxy investigations to fully understand these phenomena. [ABSTRACT FROM AUTHOR]

In Dictyostelium discoideum, cells that become part of the stalk or basal disc display behaviour that can be interpreted as altruistic. Atzmony et al. (Curr Sci 72:142-145, 1997) had hypothesised that this behaviour could be the outcome of an adaptive strategy based on differing intrinsic quality as reflected by phenotypes that indicate differences in potential for survival and reproduction, followed by intercellular competition among amoebae of differing qualities. Low-quality amoebae would have a poor chance of succeeding in the competition to form spores; they could enhance their chances of survival by adopting a presumptive stalk strategy. Here we extend the hypothesis by making use of recent findings. Our approach is based on the view that an evolutionary explanation for the apparent altruism of stalk cells in D. discoideum must apply broadly to other cellular slime moulds (CSMs) that exhibit stalk cell death. Further, it must be capable of being modified to cover social behaviour in CSMs with an extracellular stalk, as well as in sorocarpic amoebae whose stalk cells are viable. With regard to D. discoideum, we suggest that (a) differentiation-inducing factor, thought of as a signal that inhibits amoebae from forming spores and induces them to differentiate into basal disc cells, is better viewed as a mediator of competition among post-aggregation amoebae and (b) the products of the 'recognition genes', tgrB and tgrC, allow an amoeba to assess its quality relative to that of its neighbours and move to a position within the aggregate that optimises its reproductive fitness. From this perspective, all cells behave in a manner that is 'selfish' rather than 'altruistic', albeit with different expectations of success. [ABSTRACT FROM AUTHOR]

This is a review of over 400 published research papers on free-living, non-testate amoebae during the approximate last half century (1965-2017) particularly focusing on three topics: Biogeography, Ecology, and Physiology. These topics were identified because of the substantial attention given to them during the course of the last half century, and due to their potential importance in issues of local and global expanse, such as: aquatic and terrestrial stability of habitats, ecosystem processes, biogeochemistry and climate change, and the role of eukaryotic microbes generally in ecosystem services. Moreover, there are close epistemological and thematic ties among the three topics, making a synthesis of the published research more systematic and productive. The number of reviewed publications for each of the three individual topics is presented to illustrate the trends in publication frequencies during the historical period of analysis. Overall, the number of total publications reviewed varied somewhat between 1965 and early 2000 (generally less than 10 per year), but increased to well over 10 per year after 2000. The number of Biogeography and Ecology studies identified in the online citations increased substantially after the mid 1990s, while studies focusing on Physiology were relatively more abundant in the first decade (1965-1974) and less were identified in the 1985 to 2004 period. Citations to the literature are listed in tables for each of the three topics for convenience in retrieving references to specific aspects, and representative examples of the cited research in the tables are reviewed in the text under subheads dedicated to each of the three topics. Biogeographic studies largely focused on the geographic distribution and localized patterns of occurrence of amoebae, with more recent studies incorporating more attention to likely correlates with environmental and biotic factors in the distribution and community composition of amoebae. Ecological studies reviewed in the later decades tended to focus more on community dynamics, the effects of environmental variables on communities (including climate-related topics), a trend toward more physiological ecology studies, combined field-based and experimental studies, and incorporation of newer methodologies such as molecular genetics. In general, physiology studies in the first decades of the review tended to focus on topics of cell physiology such as basic biochemistry, enzyme assays, mechanisms of cell division and development, encystment, and motility. Later studies examined broader topics such as osmoregulation, nutrition, fine structure evidence of cellular changes during the life cycle (including encystment and excystment), and issues related to asexual and sexual reproduction, with increasing substantial evidence of evolutionary patterns and phylogenetics based on molecular evidence. A final section on Conclusions and Recommendations summarizes the findings and presents some potentially productive approaches to future research studies on Amoebozoa within the three designated topics of analysis. [ABSTRACT FROM AUTHOR]

Amoebae of the genus Mayorella are widespread in marine, freshwater and soil habitats. These amoebae have relatively low number of morphological characters allowing species differentiation, so the number of valid species remains rather small. Representatives of the genus Mayorella are hard to maintain in culture, the very most of them are polyphagous and carnivorous. To live and multiply they require a variety of food objects, including other protists. Thus they are difficult objects for molecular studies. Only two sequences of Mayorella were available until recently in GenBank. For the present study we isolated eight strains of Mayorella from different locations worldwide, documented them with the light microscopy and obtained complete or partial sequences of their 18S rRNA gene. Results show that all members of the genus Mayorella form a robust clade within the order Dermamoebida (Amoebozoa: Discosea). The vast majority of our strains probably represent new species; this evidences that diversity of the genus Mayorella in natural habitats is high and that this genus is rather species-rich, comprising no less than 11 species. Our results show that nowadays sequence data are necessary for reliable identification of Mayorella species. [ABSTRACT FROM AUTHOR]

This study determined the occurrence of potentially pathogenic free-living amoebae (FLA) and bacteria associated with amoebae in air-conditioning cooling towers in southern Brazil. Water samples were collected from 36 cooling systems from air-conditioning in the state of Rio Grande do Sul, Brazil. The organisms were identified using polymerase chain reaction (PCR) and sequencing automated. The results showed that these aquatic environments, with variable temperature, are potential 'hot spots' for emerging human pathogens like free-living amoebae and bacteria associated. In total, 92% of the cooling-tower samples analyzed were positive for FLA, and Acanthamoeba was the dominant genus by culture and PCR. Amoebal isolates revealed intracellular bacteria in 39.3% of them and all were confirmed as members of the genus Pseudomonas. The results obtained show the important role of cooling towers as a source of amoebae-associated pathogens. [ABSTRACT FROM AUTHOR]

It is established that the human pathogen Legionella pneumophila becomes significantly augmented for infection of macrophages after intracellular growth in amoebae when compared to like-strains cultivated in laboratory media. Based on this observation, we reasoned that the most critical virulence determinants of L.p. are expressed by responding to stimuli generated by the protozoan host specifically; a process we term "protozoan-priming." We sought to identify L.p. virulence factors that were required for replication in amoebae in order to highlight the genes necessary for production of the most infectious form of the bacterium. Using a transposon mutagenesis screen, we successfully identified 12 insertions that produced bacteria severely attenuated for growth in amoebae, while retaining a functional Dot/Icmtype IVb secretion system. Seven of these insertion mutants were found dispensable for growth in macrophages, revealing attractive therapeutic targets that reside upstream of the pathogen-human interface. Two candidates identified, lpg0730 and lpg0122 were required for survival and replication in amoebae and macrophage host cells. Both genes are conserved among numerous important human pathogenic bacteria that can persist or replicate in amoebae. Each gene encodes a component of an ATP binding cassette (ABC) transport complex of unknown function. We demonstrate the lpg0730 ortholog in Francisella tularensis subsp. novicida to be essential for colonization of both protozoan and mammalian host cells, highlighting conserved survival mechanisms employed by bacteria that utilize protozoa as an environmental reservoir for replication. [ABSTRACT FROM AUTHOR]

Free-living amoebae (FLA) are ubiquitous protozoa found worldwide in the environment. They feed by phagocytosis on various microorganisms. However, some bacteria, i.e., amoebae-resistant bacteria (ARB) or bacterial endocytobionts, can resist phagocytosis and even multiply inside FLA. This study investigated the diversity of culturable FLA in various soils from agricultural and mining sites and their bacterial endocytobionts. FLA were cultured on non-nutrient agar with alive Escherichia coli and identified by PCR and sequencing. Amoebae were lysed and bacterial endocytobionts were cultured on TSA 1/10 and Drigalski medium. Bacterial isolates were identified by PCR and 16S rDNA sequencing and characterized for their antibiotic resistance properties. To measure bacterial virulence, the amoebal model Dictyostelium discoideum was used. The analysis of FLA diversity showed that Tetramitus was the most prevalent genus in agricultural soil from Burkina Faso (73%) and garden soil from Vietnam (42%) while Naegleria and Acanthamoeba were dominant genera in mining soil from Vietnam (55%) and French alpine soil (77%). Some genera were only present in one out of the four soils analyzed. The bacterial endocytobiont included Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Human opportunistic pathogens identified as Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Burkholderia cepacia were found associated with amoebae including Micriamoeba, Tetramitus, Willaertia, or Acanthamoeba. Some of these bacteria showed various antibiotic resistance phenotypes and were virulent. Our study confirms that the occurrence of these opportunistic bacteria with FLA in soils may be important for the survival, multiplication, and spread of pathogens in the environment. [ABSTRACT FROM AUTHOR]

A high diversity of microorganisms is encountered inside dental unit waterlines (DUWL). Among those the presence of free-living amoebae (FLA) appears currently underestimated, although human infections may occur due to contact with FLA-contaminated water during dental cares. In order to limit microbial DUWL contamination, disinfectants are provided by dental unit manufacturer, however, with limited documentation on their activities against FLA. The aim of this study was to evaluate the efficiency of three commercial DUWL disinfectants: the CalbeniumC©Airel, Champigny-sur-Marne, France), the Oxygenal 6© (Kavo, Biberach, Germany) and the Sterispray© (Gammasonic, Billom, France), against two FLA species, i.e. Acanthamoeba castellanii and Vermamoeba vermiformis alone or co-cultured with Pseudomonas aeruginosa and Candida albicans at concentrations ranging from 0% to 5% (v/v). Results showed varied efficacies of disinfectants: the Oxygenal 6© did not exhibit FLA killing activity, while the Sterispray© and the Calbenium© displayed concentration- and species-dependent activities with a maximum eradication rates of 100% and 86%, and 79% and 97% for A. castellani and V. vermiformis, respectively. None of the disinfectants were able to totally eradicate FLA at concentrations recommended by manufacturers. Present results highlight unsatisfactory anti-FLA activities of 3 DUWL disinfectant preparations advocating deeper investigation of antimicrobial spectra of commercial disinfectants in use for DUWL maintenance. [ABSTRACT FROM AUTHOR]

Bovine tuberculosis (TB) is a zoonotic disease caused by Mycobacterium bovis. Despite intensive TB control campaigns, there are sporadic outbreaks of bovine TB in regions declared TB free. It is unclear how M. bovis is able to survive in the environment for long periods of time. We hypothesized that Free-living amoebae (FLA), as ubiquitous inhabitants of soil and water, may act as long-term reservoirs of M. bovis in the environment. In our model, M. bovis would be taken up by amoebal trophozoites, which are the actively feeding, replicating and mobile form of FLA. Upon exposure to hostile environmental conditions, infected FLA will encyst and provide an intracellular niche allowing their M. bovis cargo to persist for extended periods of time. Here, we show that five FLA species ( Acanthamoeba polyphaga, Acanthamoeba castellanii, Acanthamoeba lenticulata, Vermamoeba vermiformis and Dictyostellium discoideum) are permissive to M. bovis infection and that the M. bovis bacilli may survive within the cysts of four of these species for over 60 days. We further show that exposure of M. bovis-infected trophozoites and cysts to Balb/c mice leads to pulmonary TB. This work describes for the first time that FLA carrying M. bovis can transmit TB. [ABSTRACT FROM AUTHOR]

Background: Suboptimal agreement between molecular assays for the detection of Acanthamoeba spp. in clinical specimens has been demonstrated, and poor assay sensitivity directly imperils the vision of those affected by amoebic keratitis (AK) through delayed diagnosis. We sought to develop and validate a single Taqman real time PCR assay targeting the Acanthamoeba 18S rRNA gene that could be used to enhance sensitivity and specificity when paired with reference assays. Methods: Biobanked DNA from surplus delinked AK clinical specimens and 10 ATCC strains of Acanthamoeba was extracted. Sequence alignment of 66 18S rRNA regions from 12 species of Acanthamoeba known to cause keratitis informed design of a new TaqMan primer set. Performance of the new assay was compared to the 2 assays used currently in our laboratory. Results: Among 24 Acanthamoeba-positive and 83 negative specimens by the CDC reference standard, performance characteristics of the newly designed primer set were as follows: sensitivity 100%, specificity 94%, PPV 82.8%, and NPV 100%. Compared to culture, sensitivity of the new primer set was 100%, and specificity 96%. No cross-reactivity of the primer set to non-acanthamoebae, including Balamuthia and Naegleria, was found. Conclusions: We have validated a real time PCR assay for the diagnosis of AK, and in doing so, have overcome important barriers to rapid and sensitive detection of acanthamoebae, including limited sensitivity and specificity of commonly used assays. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to compare between slow and rapid sand filters for the removal of free-living amoebae during drinking water treatment production. Methods: Overall, 48 water samples were collected from two drinking water treatment plants having two different filtration systems (slow and rapid sand filters) and from inlet and outlet of each plant. Water samples were collected from Fayoum Drinking Water and Wastewater Holding Company, Egypt, during the year 2015. They were processed for detection of FLAs using non-nutrient agar (NNA). The isolates of FLAs were microscopically identified to the genus level based on the morphologic criteria and molecularly confirmed by the aid of PCR using genus-specific primers. Results: The percentage of removal for FLAs through different treatment processes reached its highest rate in the station using slow sand filters (83%), while the removal by rapid sand filter system was 71.4%. Statistically, there was no significant difference (P=0.55) for the removal of FLAs between the two different drinking water treatment systems. Statistically, seasons had no significant effect on the prevalence of FLAs in the two different drinking water treatment plants. Morphological identification of the isolated FLAs showed the presence of 3 genera namely Acanthamoeba, Naegleria, and Vermamoeba (Hartmannella) confirmed by PCR. Conclusion: The appearance of FLAs especially pathogenic amoebae in completely treated drinking water may cause potential health threat although there is no statistical difference between the two examined drinking water filtration systems. [ABSTRACT FROM AUTHOR]

Free-Living Amoebae (FLA) are widely distributed protozoa in the environment and have been isolated from many sources such as dust, soil and water. Among the pathogenic genera included in this group Acanthamoeba spp., Naegleria fowleri and Balamuthia mandrillaris have been reported to be causative agents of lethal encephalitis, disseminated infections and keratitis. Naegleria fowleri is a pathogenic FLA species which causes Primary Amoebic Meningoencephalitis (PAM). At present there are not many available data on the distribution of Naegleria species in Spain from environmental sources. Therefore, the aim of this study was to evaluate the presence of this genus in recreational water sources in the island of Tenerife, Canary Islands, Spain. In this study, ten samples collected from recreational water fountains were checked for the presence of Naegleria spp. using morphological and molecular identification tools. From the analysed samples, only one sample (seawater fountain) was positive for Naegleria spp. interestingly, not many reports of Naegleria spp. in seawater are available in the literature and thus awareness should be raised among the environmental and public health professionals. [ABSTRACT FROM AUTHOR]

The interactions that occur between bacteria and amoebae can give through mutual relations, where both organisms benefit from the association or parasitic in which one organism benefits at the expense of the other. When these organisms share the same environment, it can result in some changes in the growth of organisms, in adaptation patterns, in morphology, development or even in their ability to synthesize proteins and other substances. In this study, the interaction between Acanthamoeba polyphaga and Staphylococcus aureus (MRSA) was evaluated using a co-culture model at different incubation times. The results showed that 89% of amoebic cells remained viable after contact with the bacteria. The bacterial isolate was visualized inside the amoeba through confocal microscopy and fluorescence for up to 216 h of co-cultivation. The lysate of amoebic culture increased the growth of S. aureus (MRSA), and the effect of supernatant of culture inhibited bacterial growth over the incubation times, suggesting that A. polyphaga produced some metabolite, that inhibited the growth of bacteria. Moreover, the encystment of the A. polyphaga was increased by the bacteria presence. The results show that A. polyphaga and S. aureus interaction may have an important influence on survival of both, and specially indicate a possible effect on the metabolics characteristics each other. [ABSTRACT FROM AUTHOR]

Background: Swimming in contaminated water was reported to be associated with Acanthamoeba and N. fowleri human infections. The present study was carried out with the aim of isolation and identification of the different species of Acanthamoeba and Naegleria from two swimming pools in Alexandria University. Methods: Samples were collected from the swimming pools of Alexandria University Stadium and Faculty of Agriculture-Alexandria University during the period from May 2012 to April 2013. Results: Free-living amoebae were prevalent in the collected samples. Molecular characterization confirmed the identity of ten Acanthamoeba isolates and seven Naegleria isolates. Acanthamoeba T3, T4, T5, T11 and T15 genotypes were identified. Acanthamoeba T4 was the most prevalent genotype. Conclusion: The relatively high prevalence of Acanthamoeba, especially genotype T4, indicates the presence of a health hazard to swimmers particularly those wearing contact lenses. Naegleria fowleri was not found during the present study. [ABSTRACT FROM AUTHOR]

Five amoeboid organisms of different origin (isolated from fish organs, soil and digestive tract of earthworm) that shared light microscopical and ultrastructural features including type and arrangement of mitochondrial cristae were subjected to phylogenetic analyses based on sequences of SSU rDNA and protein coding genes (actin, cytochrome oxidase I, and eukaryotic elongation factor 2). The reconstruction of multigene phylogeny of the strains studied (i) revealed that they belong to the same single-genus Copromyxa clade; (ii) strongly supported position of Copromyxa cantabrigiensis (syn. Hartmannella cantabrigiensis) within the genus; (iii) together with comparisons of light and electron microscopy data justified reclassification of Cashia limacoides (syn. Vexillifera expectata) to Copromyxa limacoides n. comb., and (iv) justified description of a new species, Copromyxa laresi n. sp. [ABSTRACT FROM AUTHOR]

The effect of bog water table on the species structure of sphagnobiontic testate amoebae communities has been studied in peatland ecosystems of European Russia. On this basis, a transfer function (model) for quantitative paleoreconstructions has been developed. This involved the formation of a training dataset, construction of models, and testing their performance. As a result, the model constructed by weighted averaging regression has been adopted as optimal. [ABSTRACT FROM AUTHOR]

Archaeologists have long been interested in the Lake Stanley lowstand event (∼10-8 ka) in the Lake Huron basin, as archaeological sites from the Late Paleoindian/Early Archaic cultural periods were inundated by subsequent high water levels. Recent archaeological and paleoenvironmental investigations of this submerged landscape have documented stone structures that were likely utilized for caribou hunting by these cultural groups during the late Lake Stanley lowstand phase of Lake Huron. In 2011 and 2012, a total of 67 core, sediment, and rock samples were collected in a 50 km2 area by divers and a ponar sampler deployed from a survey vessel. These samples were analyzed for sediment size, sorting, morphology and source, organic and carbonate content, testate amoebae, and organic materials. A series of indicators, including distinct microfossil assemblages (such as species only found in sphagnum moss and boggy arctic ponds), rooted trees (tamarack and spruce), and charcoal (ca. 8-9000 yr old) reveal a series of microenvironments that are consistent with a subarctic climate. The analysis of the Alpena-Amberley Ridge provides a detailed picture of the environment exploited by ancient peoples during the Lake Stanley lowstand period. The methodologies employed in this study can in turn help identify other unique microregions that may yield more archaeological sites with less obvious archaeological footprints. [ABSTRACT FROM AUTHOR]

The genus Sappinia comprises free-living amoebae occurring worldwide in a variety of habitats such as soils, plant matter and freshwater ponds, but also animal faeces, and includes at present three species, S. pedata, S. diploidea and S. platani. The genus is potentially pathogenic, as indicated by the identification of S. pedata in a case of human amoebic encephalitis. Electron microscopy studies on some strains already revealed intracellular bacteria in Sappinia. In the current study, we performed 16S ribosomal RNA gene (rDNA) analysis of these bacterial endosymbionts. We first inferred relationships among Sappinia strains on the basis of 18S rDNA, demonstrating that S. pedata emerged as sister to a larger clade including S. diploidea, S. platani and a few ' S. diploidea-like' strains. Thus, bacterial 16S rDNA was searched for in representative strains of each Sappinia species/subgroup. We found that Sappinia strains were associated to distinct species of Flavobacterium or Pedobacter (phylum Bacteroidetes). These appear to be distributed following the amoebal host subgroups, and are not directly related to other Bacteroidetes species known as interacting with free-living amoebae. While all the endosymbionts' close relatives are known to grow on agar, bacteriological media inoculated with amoebal extracts remained negative. Overall, results indicate that the recovered bacteria are likely specific obligate endosymbionts of Sappinia species. Further studies, including additional amoebal strains and deep morphological and molecular analyses, will be necessary to confirm this hypothesis. [ABSTRACT FROM AUTHOR]

Sex is beneficial in eukaryotes as it can increase genetic diversity, reshuffle their genomes, and purge deleterious mutations. Yet, its evolution remains amystery. The eukaryotic clade supergroup Amoebozoa encompasses diverse lineages of polymorphic amoeboid forms, including both free-living and parasitic lineages. The group is generally believed to be asexual, though recent studies show that someof itsmembers are implicated in cryptic forms of sexual cycles. In this study, weconduct a comprehensive inventory and analysis of genes involved in meiosis and related processes, in order to investigate the evolutionary history of sex in the clade. We analyzed genomic and transcriptomic data of 39 amoebozoans representing all major subclades of Amoebozoa. Our results show that Amoebozoa possess most of the genes exclusive to meiosis but lack genes encoding synaptonemal complex (SC). The absence of SC genes is discussed in the context of earlier studies that reported ultrastructural evidence of SC in some amoebae. We also find interclade and intrageneric variation in sex gene distribution, indicating diversity in sexual pathways in the group. Particularly, members of Mycetozoa engage in a novel sexual pathway independent of the universally conserved meiosis initiator gene, SPO11. Our findings strongly suggest that not only do amoebozoans possess sex genes in their genomes, but also, based on the transcriptome evidence, the present sex genes are functional. We conclude that Amoebozoa is ancestrally sexual, contrary to the long held belief that most of itsmembers are asexual. Thus, asexuality in Amoebozoa, if confirmed to be present, is a derived-trait that appeared later in their evolution. [ABSTRACT FROM AUTHOR]

Testate amoebae are valued for their functional significance and application as indicators of environmental conditions, particularly in peatland ecosystems. Research on testate amoebae has increased dramatically in recent years but there are still large parts of the world which have seen very little research. Here we consider testate amoeba communities of the West Siberian Lowland, the world's largest peatland region and therefore one of the largest potential habitats for testate amoebae. Extensive sampling identified 89 taxa and showed that testate amoeba communities are structured by their physical and biological environment. We identified significant relationships between amoeba communities and both moisture content and vegetation composition. Despite the assemblages containing many widely-distributed species, some taxa considered typical of peatlands (e.g. Archerella flavum and Hyalosphenia papilio) were comparatively rare or absent, paralleling findings further south in Asia. We suggest that testate amoebae in this region deserve further study and may have useful applications in palaeoecological reconstruction and as bioindicators of the impacts of oil and gas extraction. [ABSTRACT FROM AUTHOR]

Species diversity in most protistan groups has been underestimated. Many morpho-species are in fact complexes that require detailed morphometric studies to be discriminated. However, which traits can be used for species descriptions remains in many cases unclear. The testate amoeba genus Quadrulella produces self-secreted, siliceous plates with a very characteristic square shape-such plates were assumed to be synapomorphic of the genus. Here we demonstrate that Quadrulella symmetrica (the most common Holarctic species) is not monophyletic. Square plate size and arrangement, test size and general shape are efficient criteria for species discrimination. Based on morphology and sequence data, we describe Quadrulella variabilis sp. nov. from Switzerland, and Quadrulella madibai sp. nov. from South Africa, and confirm the validity of Q. alata. The former species Q. subcarinata does not belong to the genus Quadrulella. We therefore transfer this species to the new genus Mrabella gen. nov. Our results show that hyalosphenids presenting siliceous square shell plates do not form a monophyletic clade. Several possible hypotheses about the origins of square plates are discussed. Additionally, this comprehensive phylogenetic analysis of the family Hyalospheniidae confirms that the genus Nebela is paraphyletic and needs to be divided into genera based on general shell shape: Nebela sensu stricto, Longinebela gen. nov., Planocarina gen. nov., Gibbocarina gen. nov., Cornutheca gen. nov. and Mrabella gen. nov. [ABSTRACT FROM AUTHOR]

Free living amoebae (FLA) are protists ubiquitously present in the environment. Aspergillus fumigatus is a mould responsible for severe deep-seated infections, and that can be recovered in the same habitats as the FLA. By conducting coculture experiments and fungal incubation with amoebal supernatants, we report herein that Vermamoeba vermiformis, a FLA present in hospital water systems, promotes filamentation and growth of A. fumigatus. This finding is of particular importance to institutions whose water systems might harbor FLA and could potentially be used by immunocompromised patients. Also, the relationships between V. vermiformis and A. fumigatus were compared to those between this fungus and two other phagocytic cells: Acanthamoeba castellanii, another FLA, and macrophage-like THP-1 cells. After 4 h of coincubation, the percentages of the three phagocytic cell types with adhered conidia were similar, even though the types of receptors between FLA and macrophagic cell seemed different. However, the percentage of THP-1 with internalized conidia was considerably lower (40 %) in comparison with the two other cell types (100 %). Thus, this study revealed that interactions between A. fumigatus and these three phagocytic cell types show similarities, even though it is premature to extrapolate these results to interpret relationships between A. fumigatus and macrophages. [ABSTRACT FROM AUTHOR]

The maintenance of biodiversity in dynamic landscapes can be explained through the unifying concept of the metacommunity, an ecological system with a changing structure that arises from both the biotic features of its component species and from changing temporal processes. We evaluated the relative importance of environmental factors and spatial factors on the structure of metacommunities of zooplankton in a Neotropical floodplain system, in relation to hydrological dynamics and potential connections among lakes. Zooplankton was sampled from 16 to 22 shallow lakes during droughts and floods in two hydrologically contrasting years. Copepods appeared to be more limited by their dispersal potential, while testate amoebae and rotifers seemed to be controlled mostly by environmental variables. These findings stress the importance of the species sorting metacommunity paradigm for groups with the smallest propagules and adult body sizes. The importance of environmental factors rather than spatial factors was apparent during floods, likely due to the facilitation of animal dispersal by floods. Our results demonstrate that the importance of these factors depends on both the functional traits of major zooplankton groups and the hydrological dynamics of the region. [ABSTRACT FROM AUTHOR]

Terpenes are structurally diverse natural products involved in many ecological interactions. The pivotal enzymes for terpene biosynthesis, terpene synthases (TPSs), had been described only in plants and fungi in the eukaryotic domain. In this report, we systematically analyzed the genome sequences of a broad range of nonplant/nonfungus eukaryotes and identified putative TPS genes in six species of amoebae, five of which are multicellular social amoebae from the order of Dictyosteliida. A phylogenetic analysis revealed that amoebal TPSs are evolutionarily more closely related to fungal TPSs than to bacterial TPSs. The social amoeba Dictyostelium discoideum was selected for functional study of the identified TPSs. D. discoideum grows as a unicellular organism when food is abundant and switches from vegetative growth to multicellular development upon starvation. We found that expression of most D. discoideum TPS genes was induced during development. Upon heterologous expression, all nine TPSs from D. discoideum showed sesquiterpene synthase activities. Some also exhibited monoterpene and/or diterpene synthase activities. Direct measurement of volatile terpenes in cultures of D. discoideum revealed essentially no emission at an early stage of development. In contrast, a bouquet of terpenes, dominated by sesquiterpenes including β-barbatene and (E,E)-α-farnesene, was detected at the middle and late stages of development, suggesting a development-specific function of volatile terpenes in D. discoideum. The patchy distribution of TPS genes in the eukaryotic domain and the evidence for TPS function in D. discoideum indicate that the TPS genes mediate lineage-specific adaptations. [ABSTRACT FROM AUTHOR]

Aim To assess the largely neglected patterns and causes of latitudinal diversity gradients in soil protists, using South American testate amoebae as model organisms. Location South-western South America (SSA). Methods We assessed the relationship among richness, latitude and predictions of eight ecological hypotheses in SSA, a region characterized by harsh abiotic conditions northward and southward from mid-latitudes. We also examined the patterns of latitudinal variation in species range sizes, species composition and phylogenetic relatedness among species to assess whether the responses of species to current climate rely on evolutionary constraints. Results Richness followed a unimodal trend with abrupt declines northward and southward from mid-latitudes. This trend was mostly explained by water-energy balance. To our knowledge, this mechanism has never been reported for soil microorganisms before. Species range sizes were larger northward and southward from mid-latitudes, a pattern which we have called the 'two-way Rapoport effect'. Species composition was due to turnover at mid-latitudes and to nestedness towards low and high latitudes. Species at mid-latitudes tended to be less related to each other than those at low and high latitudes, supporting the existence of evolutionary constraints to water-energy availability. Main conclusions The unimodal response of species diversity to water and energy availability stems from a combination of the ancestral adaptation of testate amoebae to warm, humid climates and past climate changes that set up permanent harsh abiotic conditions northward and southward from mid-latitudes. Given that other soil microorganisms also depend on water and energy to survive and reproduce, we predict that the unimodal response to water-energy balance observed will also be valid for a large number of microbial groups in SSA. While this diversity trend may not hold true for testate amoebae from other regions, we predict that their evolutionary constraints to water-energy availability will always produce strong relationships among richness, water and energy at large spatial-scales. [ABSTRACT FROM AUTHOR]

Forty different sites, represented by 1483 samples, ranging from Alaska eastwards to Siberia, have been studied to assess the circumpolar testate amoebae species diversity. A total of 378 species have been recorded. The most common taxa are cosmopolitan and are widely distributed across various arctic habitats. Statistical analysis of testate amoebae species at sites across the Arctic have yielded geographic clusters of sampling sites that have been matched with climatic regions in the Arctic. We put forward the hypothesis that the differences in testate amoebae diversity across the Arctic hint to the existence of protozoological arctic regions. The problems concerning the question of the origin of the testate amoebae in the Arctic are also discussed, with emphasis on two arctic flagship species. [ABSTRACT FROM AUTHOR]

Hyalospheniids are among the most common and conspicuous testate amoebae in high-latitude peatlands and forest humus. These testate amoebae were widely studied as bioindicators and are increasingly used as models in microbial biogeography. However, data on their diversity and ecology are still very unevenly distributed geographically: notably, data are lacking for low-latitude peatlands. We describe here a new species, Nebela jiuhuensis, from peatlands near the Middle Yangtze River reach of south-central China with characteristic morphology. The test (shell) has hollow horn-like lateral extensions also found in N. saccifera, N. equicalceus (=N. hippocrepis), and N. ansata, three large species restricted mostly to Sphagnum peatlands of Eastern North America. Mitochondrial cytochrome oxidase ( COI) data confirm that N. jiuhuensis is closely related to the morphologically very similar North American species N. saccifera and more distantly to N. ansata within the N. penardiana group. These species are all found in wet mosses growing in poor fens. Earlier reports of morphologically similar specimens found in South Korea peatlands suggest that N. jiuhuensis may be distributed in comparable peatlands in Eastern Asia (China and Korea). The discovery of such a conspicuous new species in Chinese peatlands suggests that many new testate amoebae species are yet to be discovered, including potential regional endemics. Furthermore, human activities (e.g., drainage, agriculture, and pollution) have reduced the known habitat of N. jiuhuensis, which can thus be considered as locally endangered. We, therefore, suggest that this very conspicuous micro-organism with a probably limited geographical distribution and specific habitat requirement should be considered as a flagship species for microbial biogeography as well as local environmental conservation and management. [ABSTRACT FROM AUTHOR]

The waterborne pathogenLegionella pneumophilagrows as a biofilm, freely or inside amoebae. Cyclic-di-GMP (c-di-GMP), a bacterial second messenger frequently implicated in biofilm formation, is synthesized and degraded by diguanylate cyclases (DGCs) and phosphodiesterases (PDEs), respectively. To characterize the c-di-GMP-metabolizing enzymes involved inL. pneumophilabiofilm regulation, the consequences on biofilm formation and the c-di-GMP concentration of each corresponding gene inactivation were assessed in the Lens strain. The results showed that one DGC and two PDEs enhance different aspects of biofilm formation, while two proteins with dual activity (DGC/PDE) inhibit biofilm growth. Surprisingly, only two mutants exhibited a change in global c-di-GMP concentration. This study highlights that specific c-di-GMP pathways controlL. pneumophilabiofilm formation, most likelyviatemporary and/or local modulation of c-di-GMP concentration. Furthermore, Lpl1054 DGC is required to enable the formation a dense biofilm in response to nitric oxide, a signal for biofilm dispersion in many other species. [ABSTRACT FROM AUTHOR]

Background: The World Health Organization estimates that about 3.5 billion people worldwide are affected by intestinal parasitic infections. Reports have already emphasized the role of immigrants in outbreaks of parasitic diseases in industrialized countries. With the mass influx of immigrants to Qatar, patent intestinal parasitic infections have been observed. Herein, the prevalence of intestinal protozoan infections was analysed in 29,286 records of subjects referred for stool examination at the Hamad Medical Corporation over the course of a decade (2005 to 2014, inclusive).Results: Overall prevalence of combined protozoan infections was 5.93 % but there were significant temporal trends, age and sex effects and those arising from the region of origin of the subjects. The most common protozoan was Blastocystis hominis (overall prevalence 3.45 %). Giardia duodenalis, Chilomastix mesnili, Entamoeba coli, Entamoeba hartmanni, Endolimax nana, Iodamoeba butschlii, Entamoeba histolytica/dispar, Cryptosporidium sp. and a single case of Isospora were also detected. The prevalence of combined protozoan infections, G. duodenalis and the non-pathogenic amoebae all declined significantly across the decade. That of B. hominis varied between years but showed no directional trend across years and there was no evidence that prevalence of E. histolyitica/dispar changed significantly. Protozoan infections were observed among all regional groups, but prevalence was higher among subjects from the Arabian Peninsula, Africa and Asia compared to those from the Eastern Mediterranean and Qatar. Prevalence was higher among male subjects in all cases, but age-prevalence profiles differed between the taxa.Conclusion: These results offer optimism that prevalence will continue to decline in the years ahead. [ABSTRACT FROM AUTHOR]

In the water bodies of Ukraine, 6 new species of naked amoebae were found: Saccamoeba sp., Ripella sp., Vannella lata Page, 1988, Th ecamoeba sp., Acanthamoeba sp., Vahlkampfi a sp. According to the current taxonomy, they belong to 3 classes, 4 orders, 5 families and 6 genera. New localities and original descriptions of the species are presented, along with brief characteristics of the corresponding genera. Th ecamoeba sp. and Acanthamoeba sp. are fi rst reported from the territory of Ukraine. [ABSTRACT FROM AUTHOR]

The R ickettsiae comprise intracellular bacterial symbionts and pathogens infecting diverse eukaryotes. Here, we provide a detailed characterization of ' C andidatus Jidaibacter acanthamoeba', a rickettsial symbiont of A canthamoeba. The bacterium establishes the infection in its amoeba host within 2 h where it replicates within vacuoles. Higher bacterial loads and accelerated spread of infection at elevated temperatures were observed. The infection had a negative impact on host growth rate, although no increased levels of host cell lysis were seen. Phylogenomic analysis identified this bacterium as member of the M idichloriaceae. Its 2.4 Mb genome represents the largest among R ickettsiales and is characterized by a moderate degree of pseudogenization and a high coding density. We found an unusually large number of genes encoding proteins with eukaryotic-like domains such as ankyrins, leucine-rich repeats and tetratricopeptide repeats, which likely function in host interaction. There are a total of three divergent, independently acquired type IV secretion systems, and 35 flagellar genes representing the most complete set found in an obligate intracellular A lphaproteobacterium. The deeply branching phylogenetic position of ' C andidatus Jidaibacter acanthamoeba' together with its ancient features place it closely to the rickettsial ancestor and helps to better understand the transition from a free-living to an intracellular lifestyle. [ABSTRACT FROM AUTHOR]