Diversity Of Amoebae Research Articles

Diversity of Free-Living Amoebae in New Zealand Groundwater and Their Ability to Feed on Legionella pneumophila.

Free-living amoebae (FLA) are common in both natural and engineered freshwater ecosystems. They play important roles in biofilm control and contaminant removal through the predation of bacteria and other taxa. Bacterial predation by FLA is also thought to contribute to pathogen dispersal and infectious disease transmission in freshwater environments via the egestion of viable bacteria. Despite their importance in shaping freshwater microbial communities, the diversity and function of FLA in many freshwater ecosystems are poorly understood. In this study, we isolated and characterized FLA from two groundwater sites in Canterbury, New Zealand using microbiological, microscopic, and molecular techniques. Different methods for groundwater FLA isolation and enrichment were trialed and optimized. The ability of these isolated FLA to predate on human pathogen Legionella pneumophila was assessed. FLA were identified by 18S metagenomic amplicon sequencing. Our study showed that Acanthamoeba spp. (including A. polyphaga) and Vermamoeba veriformis were the main FLA species present in both groundwater sites examined. While most of the isolated FLA co-existed with L. pneumophila, the FLA populations in the L. pneumophila co-culture experiments predominantly consisted of A. polyphaga, Acanthamoeba spp., Naegleria spp., V. vermiformis, Paravahlkampfia spp., and Echinamoeba spp. These observations suggest that FLA may have the potential to act as reservoirs for L. pneumophila in Canterbury, New Zealand groundwater systems and could be introduced into the local drinking water infrastructure, where they may promote the survival, multiplication, and dissemination of Legionella. This research addresses an important gap in our understanding of FLA-mediated pathogen dispersal in freshwater ecosystems.

Presence and diversity of free-living amoebae and their potential application as water quality indicators.

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 Ι-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 Ι to VI quality, whereas the Vermamoeba species was present only in Grade Ι water. V. croatica was found exclusively in water with Grade ΙΙ 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.

Occurrence of Free-Living Amoebae in Non-Human Primate Gut.

The gut microbiome reflects health and predicts possible disease in hosts. A holistic view of this community is needed, focusing on identifying species and dissecting how species interact with their host and each other, regardless of whether their presence is beneficial, inconsequential, or detrimental. The distribution of gut-associated eukaryotes within and across non-human primates is likely driven by host behavior and ecology. To ascertain the existence of free-living amoebae (FLA) in the gut of wild and captive non-human primates, 101 stool samples were collected and submitted to culture-dependent microscopy examination and DNA sequencing. Free-living amoebae were detected in 45.4% (46/101) of fecal samples analyzed, and their morphological characteristics matched those of Acanthamoeba spp., Vermamoeba spp., heterolobosean amoeboflagellates and fan-shaped amoebae of the family Vannellidae. Sequence analysis of the PCR products revealed that the suspected amoebae are highly homologous (99% identity and 100% query coverage) with Acanthamoeba T4 genotype and Vermamoeba vermiformis amoebae. The results showed a great diversity of amoebae in the non-human primate's microbiome, which may pose a potential risk to the health of NHPs. To our knowledge, this is the first report of free-living amoebae in non-human primates that are naturally infected. However, it is unknown whether gut-borne amoebae exploit a viable ecological niche or are simply transient residents in the gut.

Isolation of freshwater protozoan from Gomti river, Lucknow

Freshwater protozoa are integral components of aquatic ecosystems, playing crucial roles in nutrient cycling, energy flow and microbial community dynamics. Protozoa also plays vital role in food chain. The environmental condition in which protozoa can live and multiply, there is always an optimum range for each group. In this study total 7 sites were selected for water samples collection from different regions of Lucknow. During this study, total 16 species of protozoa are observed like Amoeba, Paramecium, Vorticella etc. The identification is made on the basis of the body shape, size, type of locomotion, and structure of macro and micro nucleus. With the help of recent study, we highlighted the taxonomic diversity of freshwater protozoa, including ciliates, flagellates, amoebae and sporozoans in Gomti River, Lucknow.

A needle in a haystack: A new metabarcoding approach to survey diversity at the species level of Arcellinida (Amoebozoa: Tubulinea).

Environmental DNA-based diversity studies have increased in popularity with the development of high throughput sequencing technologies. This permits the potential simultaneous retrieval of vast amounts of molecular data from many different organisms and species, thus contributing to a wide range of biological disciplines. Environmental DNA protocols designed for protists often focused on the highly conserved small subunit of the ribosome gene, that does not permit species-level assignments. On the other hand, eDNA protocols aiming at species-level assignments allow a fine level ecological resolution and reproducible results. These protocols are currently applied to organisms living in marine and shallow lotic freshwater ecosystems, often in a bioindication purpose. Therefore, in this study, we present a species-level eDNA protocol designed to explore diversity of Arcellinida (Amoebozoa: Tubulinea) testate amoebae taxa that is based on mitochondrial cytochrome oxidase subunit I (COI). These organisms are widespread in lentic water bodies and soil ecosystems. We applied this protocol to 42 samples from peatlands, estuaries and soil environments, recovering all the infraorders in Glutinoconcha (with COI data), except for Hyalospheniformes. Our results revealed an unsuspected diversity in morphologically homogeneous groups such as Cylindrothecina, Excentrostoma or Sphaerothecina. With this protocol we expect to revolutionize the design of modern distributional Arcellinida surveys. Our approach involves a rapid and cost-effective analysis of testate amoeba diversity living in contrasted ecosystems. Therefore, the order Arcellinida has the potential to be established as a model group for a wide range of theoretical and applied studies.

Evaluation of different primers of the 18S rRNA gene to profile amoeba communities in environmental samples

Amoeboid protists, an assemblage of organisms belonging to different phylogenetic lineages, have drawn increasing attention due to their crucial ecological roles in various environments and their potential health risks. Currently, 18S rRNA gene sequencing is widely applied for the detection of amoebae. However, it is not clear which is the best primer pair for 18S rRNA gene amplification in amoebae. This study compared the four most commonly used primer pairs for revealing the diversity, composition, core species, and community assembly processes of amoebae in water and sediments. We found that the choice of primers artificially influences the detection of community composition of amoebae. We also found that short-read fragments may lead to mismatches in taxonomy and were not suitable for phylogenetic analyses. In contrast, full-length primers could detect the highest number of amoeba lineages and annotate 80% of reads belonging to amoebae to known species. However, full-length primers did not detect as many amoeba species as V4 primers. Moreover, we showed that beta diversity and community assembly determination were largely unaffected by primer choice, but different primers could influence our interpretations of the ecological process underlying stochasticity and determinism. This study indicates that full-length read sequencing and V4 region Illumina sequencing are suitable for profiling amoeba diversity in the environment.

Diversity and abundance of naked lobose amoebae belonging to the classes Tubulinea and Discosea in pond sediments in Moscow urban parks

Diversity and abundance of naked lobose amoebae belonging to the classes Tubulinea and Discosea in pond sediments in Moscow urban parks

A reassessment of testate amoebae diversity in Tierra del Fuego peatlands: Implications for large scale inferences

Testate amoebae are a diverse group of shelled protists frequently used as model organisms in microbial biogeography. Relatively few species have been reported for the Southern Hemisphere, however, it remains unclear whether this lower diversity is real or an artifact of under-sampling or misidentifications, which would reduce their potential to address macroecological questions. We evaluated testate amoebae diversity from the full range of habitats occurring within two Tierra del Fuego peatlands and compared it with the reported diversity for the area and from the Northern Hemisphere peatlands. We recorded 87 species, of which 69 are new for the region and 45 of them probably new to science and likely to have restricted geographical distributions. Combined with previous studies, the total diversity of testate amoebae only from Tierra del Fuego peatlands now reaches 119, as compared with 183 reported from all Northern Hemisphere peatlands. Our results demonstrate that the number of Gondwanian and Neotropical endemic testate amoeba may be substantially higher than currently known. Previous reports of Holarctic taxa in Tierra del Fuego may result from forcing the identification of morphotypes to the descriptions in the most common literature (force-fitting) South American species into species common in literature from other regions.

The ecology of testate amoebae and Cladocera in Hawaiian montane peatlands and development of a hydrological transfer function

Peatland complexes in the humid highlands of Hawai‘i are vital refuges of biodiversity and freshwater resources. Hawaiian peat deposits are also rare repositories of terrestrial ecosystem archives located in an otherwise vast expanse of ocean. We investigated the potential for researching the paleohydrological history of Hawaiian montane peatlands on Kohala, Hawai‘i Island through analyses of testate amoebae and Cladocera. Surface peat was collected from a variety of ecohydrological habitats (from water pools to hummocks) and analyzed for modern testate amoeba and cladoceran species relative abundance. We identified 54 morphotype taxa from 21 genera of testate amoebae, 4 taxa and genera of littoral Cladocera, and the common peat rotifer Habrotrocha angusticollis. Testate amoeba diversity and morphotype occurrence mirrored observations from many high-latitude peatland studies. Constrained and unconstrained ordinations support the hypothesis that surface moisture, measured as water-table depth, is an important control on the distribution of testate amoebae and Cladocera in Hawaiian peatlands. Transfer functions relying on weighted-averaging and modern analogs were developed to predict water-table depths from species relative abundance data, and these perform well under leave-one-site-out cross-validation: RMSEP = 9.75–10.3 cm, R2 = 0.56–0.62. Including cladoceran abundance data in the calibration dataset produced modest model improvement: RMSEP = 1–8% and R2 = 2–13%. A weighted-average partial-least-squares transfer function was applied to microfossil assemblages from a 0.5 m-long peat core with a 210Pb decay chronology anchored by ten existing measurements of 210Pb activity and a Bayesian statistical framework. Microfossils were well-preserved in the peat core. The water-table depth optima of an abundant down-core taxa, Hyalosphenia subflava, is not precisely constrained in the calibration data set, but estimates match those of other tropical studies. A reconstruction of water-table depth indicates dry early nineteenth-century conditions, wet conditions in the late 19th to early twentieth centuries, followed by progressive drying for much of the twentieth-century. Testate amoeba composition appears to have been sensitive to severe drought in recent decades. The results signal that assemblages of testate amoebae and Cladocera are useful proxies of Hawaiian peatland paleohydrology and should be considered alongside other archives of Hawaiian environmental history.

The Ecology and Evolution of Amoeba-Bacterium Interactions.

Amoebae are protists that have complicated relationships with bacteria, covering the whole spectrum of symbiosis. Amoeba-bacterium interactions contribute to the study of predation, symbiosis, pathogenesis, and human health. Given the complexity of their relationships, it is necessary to understand the ecology and evolution of their interactions. In this paper, we provide an updated review of the current understanding of amoeba-bacterium interactions. We start by discussing the diversity of amoebae and their bacterial partners. We also define three types of ecological interactions between amoebae and bacteria and discuss their different outcomes. Finally, we focus on the implications of amoeba-bacterium interactions on human health, horizontal gene transfer, drinking water safety, and the evolution of symbiosis. In conclusion, amoeba-bacterium interactions are excellent model systems to investigate a wide range of scientific questions. Future studies should utilize advanced techniques to address research gaps, such as detecting hidden diversity, lack of amoeba genomes, and the impacts of amoeba predation on the microbiome.

Diversity of Naked Amoebae in Soils of Forest Areas of Zhytomyr Region (Ukraine).

Here we consider the morphotypes and changing species composition of naked amoebae in soils of forest areas in Zhytomyr region (Ukraine). The species composition and morphotypes of amoebae are influenced by the microclimate of soil and litter. Complexes of naked amoebae in the study area constitute two clusters: one of broadleaf (oak) and mixed forests, another of coniferous forests. The most similar species compositions were found in soils of oak and mixed forests (64 % similarity). The least similar were amoebae complexes of coniferous forests and oak forests, and coniferous forests and mixed forests. Non-parametric multidimensional scaling (MDS) showed that species complex of amoebae of mixed forests and oak forests had moister and more acidic soils compared to coniferous forests.

Species composition and diversity of morphotypes in epilithic biotopes of Zhytomyr region, Ukraine

16 species of naked amoebae are recorded in the eplithic biotopes of Zhytomyr region, Ukraine: Saccamoeba sp. (1), Saccamoeba sp. (2), Saccamoeba sp. (3), Cashia limacoides Page, 1974, Thecamoeba striata (Penard, 1890) Schaeffer, 1926, Thecamoeba sp., Stenamoeba stenopodia (Page, 1969) Smirnov et al., 2007, Mayorella cantabrigiensis Page, 1983, Mayorella sp., Korotnevella sp., Vexillifera sp., Vannella sp., Ripella platypodia Smirnov, Nassonova, Chao et Cavalier-Smith, 2007, Acanthamoeba sp. (1), Cochliopodium sp., Vahlkampfia sp. (1). The frequency of occurrence in samples is highest for Thecamoeba sp., Mayorella sp., Vahlkampfia sp. (1), Korotnevella sp., Vannella sp., and is lowest for Saccamoeba sp. (1), C. limacoides, M. cantabrigiensis, Cochliopodium sp., S. stenopodia, R. platypodia, T. striata, Saccamoeba sp. (2). The species and morphotype diversity of naked amoebae of the epilithic mosses and lichens is influenced by the humidity and the height above soil of the substrate. The species and morphotype diversity of naked amoebae decreases with the increase in height above soil and the decrease of humidity of substrate. We recorded naked amoebae of 9 morphotypes: monotactic, dactylopodial, fan-shaped, lens-like, lingulate, mayorellian, striate, acanthopodial, and eruptive. Amoebae of the lens-like and fan-shaped morphotypes disappear with the increase of height of substrate above soil.

The First Data on Testate Amoebae in the Coco River in Quang Nam and Da Nang Provinces, Vietnam

The first data on the species diversity of testate amoebae of the Coco River in the provinces of Quang Nam and Da Nang (Vietnam) are presented. A total of 55 species and subspecies of testate amoebae belonging to nine genera and six families have been identified in 28 samples. Species diversity of testate amoebae in plankton is higher than in benthic samples. Centropyxis aculeata (64.3%), Netzelia wailesi (39.3%), Difflugia acuminata (32.1%), Arcella discoides scutelliformis (28.6%), and Lesquereusia modesta (28.6%) are characterized by the highest frequency of occurrence. Difflugia (25), Arcella (12), Centropyxis (5), and Netzelia (4) are the most species-rich genera. The species accumulation curve based on the entire dataset is unsaturated and is described by the equation y = 12.56N0.46. The average species richness of testate amoebae per sample in plankton (13.0 ± 3.1) is statistically higher than in benthic samples (1.8 ± 1.5) (p < 0.001). The result of the redundancy analysis shows that the studied hydrochemical water parameters (temperature, pH, dissolved oxygen, electrical conductivity, and salinity) explain only 31.6% of the variation of testate amoeba diversity; the first and second axes explain 11 and 10.2% of this variation, respectively.

Prevalence of six amoeba species colonising the gills of farmed Atlantic salmon with amoebic gill disease (AGD) using qPCR

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 11:405-415 (2019) - DOI: https://doi.org/10.3354/aei00325 Prevalence of six amoeba species colonising the gills of farmed Atlantic salmon with amoebic gill disease (AGD) using qPCR Chloe J. English1,2,*, Fiona Swords3, Jamie K. Downes3, Neil M. Ruane3, Natasha A. Botwright4, Richard S. Taylor5, Andrew C. Barnes1, James W. Wynne5, Paula C. Lima4, Mathew T. Cook4 1School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia 2CSIRO Agriculture and Food, Aquaculture, Bribie Island Research Centre, 144 North Street, Woorim, QLD 4507, Australia 3Marine Institute, Rinville, Oranmore, H91 R673 Co. Galway, Ireland 4CSIRO Agriculture and Food, Aquaculture, Queensland Biosciences Precinct, 306 Carmody Road, St Lucia, QLD 4067, Australia 5CSIRO Agriculture and Food, Aquaculture, Castray Esplanade, Battery Point, TAS 7004, Australia *Corresponding author: chloe.english@csiro.au ABSTRACT: Amoebic gill disease (AGD) is the primary health concern for Atlantic salmon Salmo salar farmed in Tasmania, Australia. Neoparamoeba perurans is the aetiological agent of AGD; however, a diversity of other amoebae colonise the gills, and their role in AGD is unknown. Previous studies which document these accompanying amoebae on AGD-affected farmed Atlantic salmon relied on culture-based techniques which do not accurately determine the prevalence and abundance of these species nor whether they correlate with AGD pathology. Drawing on our previous culture-based study, here we develop and apply 5 new Taqman quantitative PCR (qPCR) assays to profile the prevalence of multiple amoeba species on the gills of AGD-affected Atlantic salmon held at 2 Tasmanian farm sites over a 1 yr period. The prevalence and abundance of N. perurans was also assessed using a previously established qPCR method. N. perurans was the dominant species, and its abundance positively correlated with the progression of gross gill pathology. Only a small number of sporadic detections of Pseudoparamoeba and Vannellida species were observed. Nolandella spp. was the notable exception, as it was the most prevalent amoeba (92%) at 1 site at 1 sample time, during which no N. perurans were detected on gills but low levels of gross gill pathology were observed. N. perurans is the predominant species and primary pathogen of AGD; however, there were instances when they were not detected on diseased gills and Nolandella spp. were highly prevalent. The significance of Nolandella spp. in relation to AGD is not yet understood. KEY WORDS: Neoparamoeba · Nolandella · Amoebozoa · AGD · Taqman qPCR · Atlantic salmon Full text in pdf format Supplementary material PreviousNextCite this article as: English CJ, Swords F, Downes JK, Ruane NM and others (2019) Prevalence of six amoeba species colonising the gills of farmed Atlantic salmon with amoebic gill disease (AGD) using qPCR. Aquacult Environ Interact 11:405-415. https://doi.org/10.3354/aei00325 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 11. Online publication date: August 22, 2019 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2019 Inter-Research.

Resistance of the oyster pathogen Vibrio tasmaniensis LGP32 against grazing by Vannella sp. marine amoeba involves Vsm and CopA virulence factors.

Vibrios are ubiquitous in marine environments and opportunistically colonize a broad range of hosts. Strains of Vibrio tasmaniensis present in oyster farms can thrive in oysters during juvenile mortality events and behave as facultative intracellular pathogen of oyster haemocytes. Herein, we wondered whether V. tasmaniensis LGP32 resistance to phagocytosis is specific to oyster immune cells or contributes to resistance to other phagocytes, like marine amoebae. To address this question, we developed an integrative study, from the first description of amoeba diversity in oyster farms to the characterization of LGP32 interactions with amoebae. An isolate of the Vannella genus, Vannella sp. AP1411, which was collected from oyster farms, is ubiquitous, and belongs to one clade of Vannella that could be found associated with Vibrionaceae. LGP32 was shown to be resistant to grazing by Vannella sp. AP1411 and this phenotype depends on some previously identified virulence factors: secreted metalloprotease Vsm and copper efflux p-ATPase CopA, which act at different steps during amoeba-vibrio interactions, whereas some other virulence factors were not involved. Altogether, our work indicates that some virulence factors can be involved in multi-host interactions of V. tasmaniensis ranging from protozoans to metazoans, potentially favouring their opportunistic behaviour.

Diversity and Distribution of Naked Amoebae in Water Bodies of Sumy Region (Ukraine)

Abstract Taxonomy of naked amoebae and specifics of their distribution in water bodies of Sumy Region are presented. Our research identified 12 species of naked amoebae of 11 morphotypes. We established their ecological groups relative to abiotic aquatic factors: euryoxidic, stenooxidic, stenobiotic and those that survive in a wide range of organic matter content. According to the species composition, swamp and riparian species complexes of naked amoebae were identified. It was found that species complexes of amoeba are influenced by such factors as temperature, concentration of dissolved oxygen and organic compounds.

Free-living amoebae and squatters in the wild: ecological and molecular features

Free-living amoebae are protists frequently found in water and soils. They feed on other microorganisms, mainly bacteria, and digest them through phagocytosis. It is accepted that these amoebae play an important role in the microbial ecology of these environments. There is a renewed interest for the free-living amoebae since the discovery of pathogenic bacteria that can resist phagocytosis and of giant viruses, underlying that amoebae might play a role in the evolution of other microorganisms, including several human pathogens. Recent advances, using molecular methods, allow to bring together new information about free-living amoebae. This review aims to provide a comprehensive overview of the newly gathered insights into (1) the free-living amoeba diversity, assessed with molecular tools, (2) the gene functions described to decipher the biology of the amoebae and (3) their interactions with other microorganisms in the environment.

Testate Amoebae of Peru: filling the gap in the Neotropics

Testate amoebae diversity from 28 surface (0-3 cm depth) soil samples found near Cuzco (6 samples), in Machu Piсchu (17 samples), in Aguas Calientes (5 samples), and one bottom sediment sample from the Lake Titicaca near the Puno collected during March of 2016 were analyzed. The 144 testate amoebae species and infra-specific taxa belonging to 27 genera were identified. Nineteen amoebae have not been identified to species levelnd likely represent new taxa. Species richness varied from one to 54 taxa per sample. The highest diversity was found in rainforests followed by those in meadows and agave habitats. The only bottom sample from Lake Titicaca has yielded two hydrobiont species from the genus Difflugia. In the course of the study, several rare species with limited geographical distribution were observed, namely Centropyxis castaneus, C. compressa, C. deflandriana, C. latideflandriana, C. cf. ohridensis, C. cf. ovoides, C. cf. pannosus, C. stenodeflandriana, Cyclopyxis plana, C. profundistoma, Apodera vas, Argynnia retorta, A. spicata, Certesella certesi, Trachelcorythion pulchellum. Our study fills a geographical gap in the distribution of some flagship species with restricted geographic distribution, e.g. Apodera vas and Certesella certesi in Peru. The results illustrate the continuity of expansion species along the Pacific coast.

The Past, Present and Future of Soil Protist Ecology Introduction to special issue

This essay introduces the special issue of this journal on the ecology of soil protists. This issue marks approximately the first 100 years of soil protistology as a discipline as some of the first studies to show that protozoa were an important part of soil ecology took place at Rothamsted, in southern England, towards the end of the first decade of the twentieth century. Much of the work on soil protists – and indeed the papers in this special issue – concentrate on traditional protozoa. In addition it is now realised that slime molds (Eumycetozoans) can potentially make an important contribution to the numbers and diversity of soil amoebae. We also argue that diatoms and other algae are likely important in soils and in need of more detailed study. By its nature microbiology (including soil protist ecology) is a science limited by technology – for example the subject could not really exist before the invention of the microscope. We suggest ways in which newer technologies (molecular methods, stable isotopes etc) may contribute to future studies on the ecology of soil protists.

Does microhabitat influence the testate amoebae communities in the Nameri National Park, northeastern India? A tropical forest perspective

The community structure of testate amoebae inhabiting different microhabitats (soil and tree-moss) within a tropical forest biome in Nameri National Park, northeastern India, was investigated. A total of 33 testate amoebae species belonging to 13 genera were identified. Species belonging to the class Lobosea constituted 73% of total testate amoebae density in the soil habitat, whereas the class Filosea constituted the most dominant forms (58%) in the moist tree-moss habitat. The relative abundance of species was higher in the tree-moss habitat compared to the soil habitats of the forest. Although multivariate analysis suggested a significant difference in assemblage patterns between the habitats, the turnover in species (i.e., beta diversity) was insignificant. Species accumulation curves (SAC) constructed using both parametric and non-parametric species richness estimators revealed that the asymptote of species richness was achieved by a low number of sample replicates in both habitats. The temperature and pH of the substratum on testate amoebae distribution patterns suggest the importance of additional background factors on testate amoebae community structure. Further studies involving more biotopes, seasons, and trophic interactions are recommended to document a complete record of testate amoebae diversity and their interactions with environmental gradients in the tropical forest biomes of northeastern India.