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]

The distribution and ecology of protosteloid amoebae are still relatively unexplored, especially in the paleotropics, despite their role in understanding the evolutionary lineage of Eumycetozoans, more commonly known as slime molds. Hence, an occurrence survey was carried out for the first time in the coastal vegetation of San Fernando City, La Union, Philippines to generate a species listing of protosteloid amoebae. Herein, a total of 40 substrate samples, comprising 20 aerial litter (AL) and 20 ground litter (GL), were collected from four collection points along the coastline of the study site to prepare for their inoculation in weak malt yeast agar (wMYA) plates. The culture plates recovered 12 species belonging to nine genera, all of which are reported as new records of protosteloid amoebae for the Philippines. This is the first study to be ever conducted on the occurrence of protosteloid amoebae in Southeast Asia. [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]

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]

Abstract An in vitro model to study the host response to Neoparamoeba perurans , the causative agent of amoebic gill disease (AGD), was evaluated. The rainbow trout gill derived cell line, RTgill-W1, was seeded onto permeable cell culture supports and maintained asymmetrically with apical seawater. Cells were inoculated with either a passage attenuated or a recent wild clone of N. perurans. Amoebae, loaded with phagocytosed fluorescent beads, were observed associated with host cells within 20 min post inoculation (pi). By 6 h small foci of cytopathic effect appeared and at 72 h cytolysis was observed, with total disruption of the cell monolayer at 96 h pi. Due to cell monolayer disruption, the platform could not support proliferation of amoebae, which showed a 3-log reduction in parasite 18S rRNA mRNA after 72 h (106 copies at 1 h to 103 at 72 h pi). SEM observations showed amoebae-like cells with either short pseudopodia and a malleiform shape, or, long pseudopodia embedded within the gill cells and erosion of the cell monolayer. To study the host immune response, inoculated gill cells were harvested from triplicate inserts at 0, 1, 3, 6, 24 and 48 h pi, and expression of 12 genes involved in the Atlantic salmon response to AGD was compared between infected and uninfected cells and between amoebic clones. Both clones induced similar host inmate immune responses, with the up-regulation of proinflammatory cytokine IL1β, complement C3 and cell receptor MHC-1. The Th2 pathway was up-regulated, with increased gene expression of the transcription factor GATA3, and Th2 cytokines IL10, IL6 and IL4/13A. PCNA and AG-2 were also up-regulated. The wild clone induced significantly higher up-regulation of IL1β, MHC-1, PCNA, lysozyme and IL10 than the attenuated clone for at least some exposure times, but AG-2 gene expression was higher in cells inoculated with the attenuated one. A principal component analysis showed that AG-2 and IL10 were key genes in the in vitro host response to N. perurans. This in vitro model has proved to be a promising tool to study host responses to amoebae and may therefore reduce the requirement for in vivo studies when evaluating alternative therapeutants to AGD control. Highlights • In vitro gill epithelia model enabled study of host response to Neoparamoeba perurans. • The association of the parasite to the monolayer was studied by SEM. • A protocol for live cell imaging of N. perurans is described. • Host cytokines related to Th2 and cell proliferative pathways were up-regulated. [ABSTRACT FROM AUTHOR]

Abstract In this study, qPCR was used to quantify opportunistic premise plumbing pathogens (OPPPs) and free-living amoebae in 11 tap water samples collected over four seasons from a city in northern China. Results demonstrated that the average numbers of gene copies of Legionella spp. and Mycobacterium spp. were significantly higher than those of Aeromonas spp. (p < 0.05). Legionella spp. and Mycobacterium spp. were 100% (44/44) positively detected while P. aeruginosa and Aeromonas spp. were 79.54% (35/44) and 77.27% (34/44) positively detected. Legionella pneumophila was only detected in 4 samples (4/44), demonstrating its occasional occurrence. No Mycobacterium avium or Naegleria fowleri was detected in any of the samples. The average gene copy numbers of target OPPPs were the highest in summer, suggesting seasonal prevalence of OPPPs. Average gene copy numbers of OPPPs in the taps of low-use-frequency were higher than in taps of high-use-frequency, but the difference was not significant for some OPPPs (p > 0.05). Moderate negative correlations between the chlorine concentration and the gene copy numbers of OPPPs were observed by Spearman analysis (r s ranged from − 0.311 to − 0.710, p < 0.05). However, no significant correlations existed between OPPPs and AOC, BDOC, or turbidity. Moderate positive correlations were observed between the target microorganisms, especially for Acanthamoeba spp., through Spearman analysis (p < 0.05). Based on our studies, it is proposed that disinfectant concentration, season, taps with different-use frequency, OPPP species, and potential microbial correlations should be considered for control of OPPPs in tap water. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A C. vulgaris semicontinuous culture in M medium, 2 m3 RW in greenhouse was proven. • Areal biomass productivity up to 26 g m−2 d−1 was reached on the third day. • Saturated fatty acids proportion (C14–C18) was increased. • 25–50 mg L−1 of NH 4 + in the medium decreased contamination risks by protozoa. Abstract A Chlorella vulgaris UTEX 26 semicontinuous culture was implemented in 2000 L raceways with M medium during spring season at greenhouse conditions. Areal biomass productivities between 20 and 26 g m−2 d−1 were reached on the third day. The maximal areal lipid productivity obtained was 6.1 g m−2 d−1 and an increment in the saturated fatty acids (SFA) proportion (C14–C18) was favored in comparison with the fatty acids obtained with M medium in photobioreactors of 1 L and photoperiod light:darkness 12:12 h. After the eighth day of the culture or biomass concentrations above 0.25 g L−1, the microalgal cultures were prone to contamination by ciliates and amoebae, due to the sugars excreted by C. vulgaris UTEX 26. The periodical addition of NH 4 HCO 3 to the microalgal culture maintained the ammonium concentration between 25 and 50 mg L−1, which contributed to diminish the contamination risks by protozoa. [ABSTRACT FROM AUTHOR]

Abstract Background The discovery of mimivirus in 2003 prompted the quest for other giant viruses of amoebae. Mimiviruses and their relatives were found to differ considerably from other viruses. Their study led to major advances in virology and evolutionary biology. Aims We summarized the widening gap between mimiviruses and other viruses. Sources We collected data from articles retrieved from PubMed using as keywords 'giant virus', 'mimivirus' and 'virophage', as well as quoted references from these articles. Content Data accumulated during the last 15 years on mimiviruses and other giant viruses highlight that there is a quantum leap between these infectious agents, the complexity of which is similar to that of intracellular microorganisms, and classical viruses. Notably, in addition to their giant structures and genomes, giant viruses have abundant gene repertoires with genes unique in the virosphere, including a tremendous set of translation components. The viruses contain hundreds of proteins and many transcripts. They share a core of central and ancient proteins but their genome sequences display a substantial level of mosaicism. Finally, mimiviruses have a specific mobilome, including virophages that can integrate into their genomes, and against which they can defend themselves through integration of short fragments of the DNA of these invaders. Implications Mimiviruses and subsequently discovered giant viruses have changed the virus paradigm and contradict many virus definition criteria delineated for classical viruses. The major cellular hallmark that is still lacking in giant viruses is the ribosome, including both ribosomal protein and RNA encoding genes, which makes them bona fide microbes without ribosomes. [ABSTRACT FROM AUTHOR]

Highlights • We find a significant relationship between water-table depth and testate amoebae community structure. • We describe testate amoebae ecology. • We develop statistically robust transfer functions, the first for Australia. • We show that the Modern Analogue Technique provides the best transfer function. • We highlight information provided by species-pruned transfer functions. Abstract Although it is well established that moisture availability in south-eastern Australia has been decreasing through time recently, the driver(s) of this trend are contentious, and our understanding of any drivers is limited by a relatively short historic record. Testate amoebae have been widely used to reconstruct peatland hydrology in the Northern Hemisphere, but in the Southern Hemisphere research is still needed to assess their proficiency as a palaeohydrological proxy and to develop robust transfer functions. Here we examine the ecology of testate amoebae in several high altitude mires in south-eastern Australia and present the first transfer function for the continent. Euglypha tuberculata type , Centropyxis platystoma type and Assulina muscorum were the most common taxa in our modern samples. Water-table depth was the primary environmental variable determining testate amoebae assemblages and therefore transfer functions were developed for this ecological factor. We found that the performance of various all-species and species-pruned transfer functions were statistically robust, with R2 values of around 0.8 and Root Mean Squared Error of Prediction (RMSEP) values of about 7 cm. All cross-validation methods (leave-one-out RMSEP, cluster-bootstrap RMSEP, segment-wise RMSEP and leave-one-site-out RMSEP from all-species and species-pruned transfer functions) suggested that the Modern Analogue Technique (MAT) was the best performing transfer function, with negligible bias evident from un-even sampling and spatial autocorrelation. We also used a new approach to evaluate the importance of taxa and the performance of our transfer functions using species-pruned methods. Our results suggest that the all-species MAT, with an RMSEP of 5.73 and R2 of 0.86, provides the best reconstruction of water-table depth across our sites in south-eastern Australia. [ABSTRACT FROM AUTHOR]

Highlights • We examine testate amoebae distribution in continuous permafrost peatlands. • Electrical conductivity is the dominant control on testate amoebae distribution. • Water-table depth is a secondary control on testate amoebae distribution. • Two new transfer functions for reconstructing WTD and conductivity are presented. Abstract Arctic peatlands represent a major global carbon store, but rapid warming poses a threat to their long-term stability. Testate amoebae are sensitive hydrological indicators that offer insight into Holocene environmental change in peatlands. However, in contrast to temperate peatlands, there have only been a few studies into the ecology of testate amoebae and their efficacy as environmental indicators in permafrost peatlands. We present the first study of testate amoeba ecology from peatlands in the continuous permafrost zone, based on samples from across the Alaskan North Slope. Multivariate statistical analyses show that pore water electrical conductivity (EC), a proxy for nutrient status along the ombrotrophic-minerotrophic gradient, is the dominant control on testate amoeba distribution. Water-table depth (WTD) is also a significant control on testate amoeba distribution, but is secondary to EC. We present two new testate amoeba-based transfer functions to reconstruct both EC (TF EC) and WTD (TF WTD), the first for peatlands in the continuous permafrost zone. The transfer functions are based on Weighted Averaging Partial Least Squares (WAPLS) regression and were assessed using leave-one-out (LOO) cross-validation. We find that both transfer functions have good predictive power. TF WTD is the best performing model (R2 JACK = 0.84, RMSEP JACK = 6.66 cm), but TF EC also performs well (R2 JACK = 0.76, RMSEP JACK = 146 μS cm−1). Our findings are similar to those conducted in peatlands in discontinuous permafrost regions. The new transfer functions open the opportunity for reconstructing the Holocene dynamics of peatlands of the continuous permafrost zone in Alaska, which represent rapidly changing ecosystems. [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 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 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]

Abstract Free-living amoebae are widespread in freshwater ecosystems. Although many studies have investigated changes in their communities across space, the temporal variability and the drivers of community changes across different habitat types are poorly understood. A total of 108 surface water samples were collected on a seasonal basis from four reservoirs and two rivers in Xiamen city, subtropical China. We used high throughput sequencing and qPCR methods to explore the occurrence and abundance of free-living amoebae. In total, 335 amoeba OTUs were detected, and only 32 OTUs were shared by reservoir and river habitats. The reservoirs and rivers harbored unique amoebae communities and exhibited distinct seasonal patterns in community composition. High abundance of the 18S rRNA gene of Acanthamoeba was observed in spring and summer, whereas the abundance was low in autumn and winter. In addition, the abundance of Hartmannella was significantly higher when isolated from reservoirs in summer/autumn and from river in spring/summer. Moreover, the temporal patterns of amoebae communities were significantly associated with water temperature, indicating that temperature is an important variable controlling the ecological dynamics of amoebae populations. However, our comparative analysis indicated that both environmental selection, and neutral processes, significantly contributed to amoeba community assembly. The genera detected here include pathogenic species and species that can act as vectors for microbial pathogens, which can cause human infections. Graphical abstract Image 1 Highlights • The habitat pattern prevails over seasonal change of amoebae community composition. • The amoebae abundance is higher in summer than winter. • Water temperature, turbidity and nutrients shape the amoebae community assembly. • Amoebae community exhibits stronger stochastic processes in reservoir than river. [ABSTRACT FROM AUTHOR]

Abstract Free-living amoebae (FLA) are widely spread in the environment and also known to cause rare but often serious infections. The present work focuses on a local survey on FLA. It is essential to know the prevalence and distribution of these microorganisms in order to get infections caused by them under control. In this study, FLA isolated from domestic tap water samples from homes of contact lens wearers were identified by morphology and by 18S rRNA gene sequence analysis. Morphological analysis and partial sequencing of the 18S rDNA revealed the presence of Acanthamoeba genotype T4 and Vermamoeba vermiformis in the investigated tap water samples. Naegleria fowleri , Balamuthia mandrillaris , and Sappinia spp. were not detected during this study. It was shown that species of FLA known to cause eye infections in humans are widely distributed in tap water in Istanbul, Turkey. Contact lens wearers should be aware of the risk of contamination from tap water and strictly apply stringent contact lens hygiene. With this study, we established Acanthamoeba genotype T4 and Vermamoeba vermiformis as contaminants of tap water in Istanbul. Graphical abstract Image Highlights • Free-living amoebae were identified by morphology and by 18S rRNA gene sequence analysis. • Acanthamoeba genotype T4 and Vermamoeba vermiformis were determined as contaminants of tap water in Istanbul. • Contact lens wearers should be aware of the risk of contamination from tap water. [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]

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]

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]

Legionella infections are among the most important waterborne infections with constantly increasing numbers of cases in industrialized countries, as a result of aging populations, rising numbers of immunocompromised individuals and increased need for conditioned water due to climate change. Surveillance of water systems is based on microbiological culture-based techniques; however, it has been shown that high percentages of the Legionella populations in water systems are not culturable. In the past two decades, the relevance of such viable but non-culturable (VBNC) legionellae has been controversially discussed, and whether VBNC legionellae can directly infect human macrophages, the primary targets of Legionella infections, remains unclear. In this study, it was demonstrated for the first time that several starved VBNC Legionella strains (four L. pneumophila serogroup 1 strains, a serogroup 6 strain and a L. micdadei strain) can directly infect different types of human macrophages and amoebae even after one year of starvation in ultrapure water. However, under these conditions, the strains caused infection with reduced efficacy, as represented by the lower percentages of infected cells, prolonged time in co-culture and higher multiplicities of infection required. Interestingly, the VBNC cells remained mostly non-culturable even after multiplication within the host cells. Amoebal infection by starved VBNC Legionella, which likely occurs in oligotrophic biofilms, would result in an increase in the bacterial concentration in drinking-water systems. If cells remain in the VBNC state, the real number of active legionellae will be underestimated by the use of culture-based standard techniques. Thus, further quantitative research is needed in order to determine, whether and how many starved VBNC Legionella cells are able to cause disease in humans. [ABSTRACT FROM AUTHOR]

The amoeba Naegleria fowleri is the causative agent of the highly fatal disease, primary amoebic meningoencephalitis, and estimated to cause 16 deaths per year in the United States alone. Colonisation of drinking water distribution systems (DWDSs) by the N. fowleri is a significant public health issue. Understanding the factors which enable this pathogen to colonise and thrive in DWDSs is critical for proper management. The microbial ecology within DWDSs may influence the ability of N. fowleri to colonise DWDSs by facilitating the availability of an appropriate food source. Using biofilm samples obtained from operational DWDSs, 16S rRNA amplicon metabarcoding was combined with genus-specific PCR and Sanger sequencing of intracellular associated bacteria from isolated amoeba and their parental biofilms to identify Meiothermus chliarophilus as a potential food source for N. fowleri . Meiothermus was confirmed as a food source for N. fowleri following successful serial culturing of axenic N. fowleri with M. chliarophilus or M. ruber as the sole food source. The ability to identify environmental and ecological conditions favourable to N. fowleri colonisation, including the detection of appropriate food sources such as Meiothermus , could provide water utilities with a predictive tool for managing N. fowleri colonisation within the DWDS. [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]

Free-living amoebae (FLA) are ubiquitous organisms present in various natural and artificial environments, such as drinking water storage towers (DWST). Some FLA, such as Acanthamoeba sp., Naegleria fowleri , and Balamuthia mandrillaris , can cause severe infections at ocular or cerebral level in addition to being potential reservoirs of other pathogens. In this work, the abundance and diversity of FLA was evaluated in two sampling campaigns: one performed over five seasons in three DWST at three different levels (surface, middle and bottom) in water and biofilm using microscopy and PCR, and one based on the kinetics analysis in phase contrast and confocal microscopy of biofilm samples collected every two weeks during a 3-month period at the surface and at the bottom of a DWST. In the seasonal study, the FLA were detected in each DWST water in densities of ~20 to 25 amoebae L −1 . A seasonal variation of amoeba distribution was observed in water samples, with maximal densities in summer at ~30 amoebae L −1 and minimal densities in winter at ~16 amoebae L −1 . The FLA belonging to the genus Acanthamoeba were detected in two spring sampling campaigns, suggesting a possible seasonal appearance of this potentially pathogenic amoeba. Interestingly, a 1 log increase of amoebae density was observed in biofilm samples collected at the surface of all DWST compared to the middle and the bottom where FLA were at 0.1–0.2 amoebae/cm 2 . In the kinetics study, an increase of amoebae density, total cell density, and biofilm thickness was observed as a function of time at the surface of the DWST, but not at the bottom. To our knowledge, this study describes for the first time a marked higher FLA density in biofilms collected at upper water levels in DWST, constituting a potential source of pathogenic micro-organisms. [ABSTRACT FROM AUTHOR]

Reclamation of domestic wastewater for agricultural irrigation is viewed as a sustainable option to create an alternative water source and address water scarcity. Free-living amoebae (FLA), which are amphizoic protozoa, are widely distributed in various environmental sources. The FLA could cause considerable environmental and health risks. However, little information is available on the risk of these protozoa. In this study, we evaluated the feasibility using rural domestic wastewater for agricultural irrigation, and analyzed dynamic changes of the microbial community structure and FLA populations in raw and treated wastewater, as well as the phyllosphere and rhizosphere of lettuce production sites that were irrigated with different water sources. The bacterial community dynamics were analyzed by terminal restriction fragment length polymorphism (T-RFLP). The bacterial community structures in the influent were similar to that in the effluent, while in some cases relative abundances varied significantly. The populations of Acanthamoeba spp. and Hartmannella vermiformis in the anaerobically treated wastewater were significantly higher than in the raw wastewater. The vegetables could harbor diverse amoebae, and the abundances of Acanthamoeba spp. and H. vermiformis in the rhizosphere were significantly higher than in the phyllosphere. Accordingly, our studies show insight into the distribution and dissemination of amoebae in wastewater treatment and irrigation practices. [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]

A seven metres thick peat bog (Misten, Hautes-Fagnes, Belgium) has been studied at high resolution in order to reconstruct the conditions of peat formation and evolution on the basis of pollen, testate amoebae analysis, and geochemistry. The sampled section of the peat bog corresponds to the most part of the Atlantic period, all the Subboreal period and the earliest Subatlantic period, i.e. a time interval between 7300 cal BP and 2000 cal BP. The identification of tie-points in the pollen assemblages recognized in a previous work (Persch, 1950) performed in the periphery of the same peat-bog, allows accurate correlation of the two sites, 460 cm thickness of peat in the central part corresponding to 230 cm thickness of peat in the periphery. The well constrained dates of the tie-points in the present work provide a more precise chronology of the events identified in Persch's pollen diagram. A comparison of pollen data in both sites demonstrates that, as expected, the Corylus pollen rain is proportionally more important and the Quercetum mixtum pollen rain proportionally less important in the central area of the peat bog than in the periphery. The study of the testate amoebae in the central part of the peat bog is the major contribution of the present work. A stratigraphically constrained analysis resulted in the identification of five biozones, the zonation being mainly built on the fluctuations observed between Archerella (Amphitrema) flavum and Difflugia pulex. Three transfer functions have been applied and compared. Coupled with the humification values of each level, it allows a very accurate approach of the water-table level, and hence of local climatic conditions, at the time of the peat formation. Combination of pollen results and testate amoebae zonal subdivisions allows the definition, dating and interpretation of 18 rather short time intervals with an approximate duration of 200 to 300 years each. Our results validate and expand a previously published climate interpretation that combined geochemical data and a preliminary testate amoebae analysis. [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]

Given any complex Laurent polynomial f , Amoeba ( f ) is the image of its complex zero set under the coordinate-wise log absolute value map. We discuss an efficiently constructible polyhedral approximation, ArchTrop ( f ) , of Amoeba ( f ) , and derive explicit upper and lower bounds, solely as a function of the number of monomial terms of f , for the Hausdorff distance between these two sets. We also show that deciding whether a given point lies in ArchTrop ( f ) is doable in polynomial-time, for any fixed dimension, unlike the corresponding problem for Amoeba ( f ) , which is NP -hard already in one variable. ArchTrop ( f ) can thus serve as a canonical low order approximation to start a higher order iterative polynomial system solving algorithm, e.g., homotopy continuation. [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]

Shigella flexneri and Shigella sonnei bacteria cause the majority of all shigellosis cases worldwide. However, their distributions differ, with S. sonnei predominating in middle- and high-income countries and S. flexneri predominating in low-income countries. One proposed explanation for the continued range expansion of S. sonnei is that it can survive in amoebae, which could provide a protective environment for the bacteria. In this study, we demonstrate that while both S. sonnei and S. flexneri can survive coculture with the free-living amoebae Acanthamoebae castellanii, bacterial growth is predominantly extracellular. All isolates of Shigella were degraded following phagocytosis by A. castellanii, unlike those of Legionella pneumophila, which can replicate intracellularly. Our data suggest that S. sonnei is not able to use amoebae as a protective host to enhance environmental survival. Therefore, alternative explanations for S. sonnei emergence need to be considered. [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]

Acanthamoeba isolated from environmental soil harbors the obligate intracellular symbiont Neochlamydia , which has a critical role in host amoebal defense against Legionella pneumophila infection. Here, by using morphological analysis with confocal laser scanning fluorescence microscopy and transmission electron microscopy, proteome analyses with two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) and liquid chromatography–mass spectrometry (LC/MS), and transcriptome analysis with DNA microarray, we explored the mechanism by which the Neochlamydia affected this defense. We observed that when rare uptake did occur, the symbiotic amoebae allowed Legionella to grow normally. However, the symbiotic amoebae had severely reduced uptake of Legionella when compared with the aposymbiotic amoebae. Also, in contrast to amoebae carrying the endosymbiont, the actin cytoskeleton was significantly disrupted by Legionella infection in aposymbiotic amoebae. Furthermore, despite Legionella exposure, there was little change in Neochlamydia gene expression. Taken together, we concluded that the endosymbiont, Neochlamydia prevents Legionella entry to the host amoeba, resulting in the host defense against Legionella infection. [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]

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]

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]

The role of human activity as a vector in the movement of soil microorganisms is uncertain and disputed. It is increasingly clear that some larger microorganisms have restricted distributions and plausible to imagine that many human activities could lead to exotic species introductions, but concrete examples are lacking. We investigated an unusual case study: the former mining settlement of Pyramiden on the island of Spitsbergen in the Svalbard archipelago. In around 1983 large quantities of chernozem soils were imported from the southern USSR as part of an urban greening initiative, bringing large numbers of soil organisms to a very different physical environment. Focusing on a readily-identifiable group of protists with documented regional endemism (testate amoebae), we assessed morphospecies assemblages after thirty years. We analysed communities from Pyramiden imported soils and conducted comparisons to: i) nearby locations with non-imported near-natural soils; ii) previously-established datasets from near-natural Svalbard soils and chernozem soils in southern Russia, and iii) regional species inventories from both regions. Our aims were to assess how the community has adapted to the change in physical conditions and identify any evidence for the import of exotic taxa. Our results show significant differences between the assemblages of imported soils and those of nearby reference sites but strict comparisons are complicated by the different treatment of soils in different locations. No taxa were identified which can be unambiguously identified as atypical for the region. Assemblages of imported soils were more similar to those of other sites on Svalbard than to assemblages from southern Russia. Our data are equivocal but suggest that the testate amoeba assemblages of soils transported more than 3000 km northwards have substantially acclimated to the new conditions, contrasting with micro-invertebrates in the same site. ‘Accidental experiments’ like the soils of Pyramiden provide unique opportunities for long-term, large-scale, soil biological research. [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]

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]

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]

In north-west Europe, large areas of open peatland have been drained and planted with spatially homogenous stands of non-native conifers. The detrimental impact of afforestation on peatland carbon and biodiversity have led to large-scale attempts to restore these landscapes back to their open, tree-less form. The responses of dominant microbial consumers − testate amoebae − to peatland forest-to-bog restoration are largely unexplored. We studied changes in testate amoebae with forest-to-bog restoration in the largest expanse of blanket bog in the UK and compared testate amoeba communities in relatively undisturbed open bog with forested and forest-to-bog restoration sites. Forested areas contained testate amoeba communities which were functionally different from open bog, characterised by a lack of mixotrophic taxa known to contribute to primary production. Seventeen years after restoration management, the microbial communities in the forest-to-bog sites remained more similar to forested areas than to the open bog community. Our results suggest that afforestation has reduced the trophic level of testate amoeba communities, which are only beginning to recover post-restoration in the wettest areas where Sphagnum has re-colonized. This study also highlights the need to consider a wide-range of reference sites to encompass the natural variability within ombrotrophic blanket bog. We conclude that testate amoebae have the potential to act as functionally-significant bio-indicators in peatlands undergoing forest-to-bog restoration. [ABSTRACT FROM AUTHOR]

Legionellae, i.e. Legionella pneumophila , are human bacterial hydrophilic facultative pathogens causing pneumonia (Legionnaires’ disease). Free-living amoebae (FLA) can serve as natural hosts and thus as reservoirs of many amoebae-resistant bacteria. An encysted amoeba can contribute to the resistance of intracellular L. pneumophila to various chemical and physical treatments. Humans can be infected by droplets containing bacteria from an environmental source or human-made devices such as shower heads, bathtubs, air-conditioning units or whirlpools. In this study, we were investigating the presence of FLA and L. pneumophila in plumbing systems of healthcare facilities in Bratislava (Slovakia) by standard diagnostic methods, while the presence of L. pneumophila was verified also by MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry) analysis. The results showed the occurrence of L. pneumophila and FLA in 62.26% and 66.4% of samples taken from four paediatric clinics, respectively. Both standard methods and MALDI-TOF MS showed comparable results and they can be successfully applied for the identification of L. pneumophila strains in environmental samples. Our approach could be useful for further monitoring, prevention and decreasing risk of Legionella infection also in other hospitals. [ABSTRACT FROM AUTHOR]