A new ballistosporous species of Protostelium

During surveys of the protostelids of the Hawaiian Islands and the South Island of New Zealand, an undescribed species of Protostelium was discovered fruiting on collections of substrates found in several sites on the southern and western parts of the island of Hawaii and from one site near Port Elizabeth, New Zealand. The new species, P. okumukumu, has a sporocarp with a bipartite stalk that supports a single, spherical spore. The basal portion of the stalk is straight and rigid. The upper part of the stalk is a nearly spherical apophysis. The junction between the stalk base and the apophysis is flexible such that the spore and apophysis swing back and forth as a unit. Spores are forcibly discharged from the stalk, and only the straight base of the stalk is left behind. Amoebae typical of the taxon Protostelium germinate from the spores, and when an amoeba differentiates into a prespore cell, it becomes lozenge shaped (nearly ellipsoid) in top view, as is typical for species of Protostelium. This represents the seventh species of protostelids described to have forcible spore discharge, and the possibility of forcible discharge needs to be examined in several other species.

[A micro-culture method for continuous observation of free-living amoebae]

OBJECTIVE

To establish a method for co-culture of amoebae and endosymbionts, also for continuously observing the microphenotype of amoebae.

METHODS

24 wells culture plate with cover glass on the wells was used as containers. Amoebae and Candida albicans were co-cultured in microdrop of medium in the wells at 37 degrees C, and observed under x1000.

RESULTS

Continuous observation revealed trophozoites in various shapes like letters T, K, or Y, their movement and ingestion phenomenon were observed.

CONCLUSION

The micro-culture method is useful in observing the amoebal morphology and its phagocytic process to Candida albicans.

The ecology of testate amoebae (Protists) in sphagnum in North-western Poland in relation to peatland ecology

We studied the relationship between testate amoebae (Protozoa) communities and the depth to the water table (DWT), pH, conductivity, and microhabitat type in Sphagnum dominated peatlands of north-western Poland and built predictive (transfer function) models for inferring DWT and pH based on the testate amoebae community structure. Such models can be used for peatland monitoring and paleoecology. A total of 52 testate amoebae taxa were recorded. In a redundancy analysis, DWT and pH explained 20.1% of the variation in the species data and allowed us to identify three groups of taxa: species that are associated with (1) high DWT and low pH, (2) low DWT and low pH, and (3) high pH and mid-range DWT. Our transfer function models allow DWT and pH to be estimated with mean errors of 9.89 cm and 0.71 pH units. The prediction error of the DWT model and the tolerance of the species both increase with increasing dryness. This pattern mirrors the ecology of Sphagnum mosses: Species growing in wet habitats are more sensitive to change in water table depth than the species growing in drier microhabitats. Our results are consistent with studies of testate amoeba ecology in other regions, and they provide additional support for the use of these organisms in paleoecological and biomonitoring contexts.

Guenther Gerisch and Dictyostelium, the microbial model for ameboid motility and multicellular morphogenesis

Beginning in 1960 and continuing to this day, Guenther Gerisch's work on the social ameba Dictyostelium discoideum has helped to make it the model organism of choice for studies of cellular activities that depend upon the actomyosin cytoskeleton. Gerisch has brought insight and quantitative rigor to cell biology by developing novel assays and by applying advanced genetic, biochemical and microscopic techniques to topics as varied as cell-cell adhesion, chemotaxis, motility, endocytosis and cytokinesis.

Amoebae in domestic water systems: resistance to disinfection treatments and implication in Legionella persistence

AIMS

Monitoring of microbial changes during and after application of various disinfection treatments in a model domestic water system.

METHODS AND RESULTS

A pilot-scale domestic water system consisting of seven galvanized steel re-circulation loops and copper dead legs was constructed. Culture techniques, confocal laser scanning microscopy after fluorescent in situ hybridization and viability staining with the BacLight LIVE/DEAD kit were used for planktonic and biofilm flora monitoring. Before starting the treatments, the system was highly contaminated with Legionella pneumophila and biofilm populations mainly consisted of beta-proteobacteria. In the water and the biofilm of the loops, continuous application of chlorine dioxide (0.5 mg l(-1)), or chlorine (2.5 mg l(-1)) were very effective in reducing the microbial flora, including L. pneumophila. Heterotrophic bacteria, although strongly reduced, were still detectable after ozone application (0.5 mg l(-1)), whereas with monochloramine (0.5 mg l(-1)) and copper-silver ionization (0.8/0.02 mg l(-1)), the contamination remained significantly higher. Monochloramine and copper-silver did not remove the biofilm. During copper-silver application, Legionella re-growth was observed. Only chlorine dioxide led to detectable effects in the dead leg. Amoebae could not be eliminated, and after interrupting the treatments, L. pneumophila quickly recovered their initial levels, in all cases.

CONCLUSIONS

Chlorine dioxide, applied as a continuous treatment, was identified in this study as the most efficient for controlling L. pneumophila in a domestic water system. Chlorine dioxide showed a longer residual activity, leading to improved performance in the dead leg. Amoebae resisted to all the treatments applied and probably acted as reservoirs for L. pneumophila, allowing a quick re-colonization of the system once the treatments were interrupted.

SIGNIFICANCE AND IMPACT OF THE STUDY

Control of microbial contamination requires maintenance of a constant disinfectant residual throughout the water system. Treatment strategies targeting free-living amoebae should lead to improved control of L. pneumophila. Such treatment strategies still have to be investigated.

Amoebae and other protozoa in material samples from moisture-damaged buildings

Mold growth in buildings has been shown to be associated with adverse health effects. The fungal and bacterial growth on moistened building materials has been studied, but little attention has been paid to the other organisms spawning in the damaged materials. We examined moist building materials for protozoa, concentrating on amoebae. Material samples (n = 124) from moisture-damaged buildings were analyzed for amoebae, fungi, and bacteria. Amoebae were detected in 22% of the samples, and they were found to favor cooccurrence with bacteria and the fungi Acremonium spp., Aspergillus versicolor, Chaetomium spp., and Trichoderma spp. In addition, 11 seriously damaged samples were screened for other protozoa. Ciliates and flagellates were found in almost every sample analyzed. Amoebae are known to host pathogenic bacteria, such as chlamydiae, legionellae, and mycobacteria and they may have a role in the complex of exposure that contributes to the health effects associated with moisture damage in buildings.

Microorganisms resistant to free-living amoebae

Free-living amoebae feed on bacteria, fungi, and algae. However, some microorganisms have evolved to become resistant to these protists. These amoeba-resistant microorganisms include established pathogens, such as Cryptococcus neoformans, Legionella spp., Chlamydophila pneumoniae, Mycobacterium avium, Listeria monocytogenes, Pseudomonas aeruginosa, and Francisella tularensis, and emerging pathogens, such as Bosea spp., Simkania negevensis, Parachlamydia acanthamoebae, and Legionella-like amoebal pathogens. Some of these amoeba-resistant bacteria (ARB) are lytic for their amoebal host, while others are considered endosymbionts, since a stable host-parasite ratio is maintained. Free-living amoebae represent an important reservoir of ARB and may, while encysted, protect the internalized bacteria from chlorine and other biocides. Free-living amoebae may act as a Trojan horse, bringing hidden ARB within the human "Troy," and may produce vesicles filled with ARB, increasing their transmission potential. Free-living amoebae may also play a role in the selection of virulence traits and in adaptation to survival in macrophages. Thus, intra-amoebal growth was found to enhance virulence, and similar mechanisms seem to be implicated in the survival of ARB in response to both amoebae and macrophages. Moreover, free-living amoebae represent a useful tool for the culture of some intracellular bacteria and new bacterial species that might be potential emerging pathogens.

Viability of amoebae, fungal conidia, and yeasts: rapid assessment by flow cytometry

Conventional methods for the evaluation of antimicrobials and disinfecting solutions with microorganisms involve culture-based techniques, which are time-consuming and underestimate the number of viable organisms. Rapid detection and viability measurements of microorganisms in homogenous and heterogenous microbial populations have been greatly enhanced by recent advances in the use of fluorescent stains in flow cytometry (FCM). FCM has been applied to enumerate, differentiate, and identify microorganisms, determine protein and DNA content of cells, analyze the physiological state of individual cells, and analyze the interaction of drugs, antibiotics, and antimicrobials with microbial cells. Four physiological states of cells can be distinguished by FCM: (1) reproductively viable, (2) metabolically active, (3) intact, and (4) permeabilized.FCM permits a rapid and quantitative measurement of the optical characteristics of cells as they pass through, in a single file, a focused beam of light. As cells are carried within a fast-flowing fluid stream and through the focus of exciting light, three parameters are measured: forward angle light scatter, side angle light scatter, and fluorescence emitted by dyes that have specific interaction with intracellular components of individual cells. FCM data that are presented in histogram and dot plots can be generated to give information on a variety of properties of interest among cells in the population as a whole.FCM offers major advantages in multiparameter data acquisition and multivariate data analysis, high-speed analysis, and cell-sorting capabilities. Disadvantages may be associated with the cost, which is usually over 100,000 (US Dollars) for a typical laser-based flow cytometer with just analyzing capabilities. Another disadvantage is that skilled personnel are usually required to operate these complex instruments so as to get optimum performance. A schematic overview of flow cytometry is presented in Fig. 1.

Plant Functional Group Diversity Promotes Soil Protist Diversity

We tested whether effects of plant diversity can propagate through food webs, down to heterotrophic protists not linked directly to plants. To this end we synthesised grassland ecosystems with varying numbers of plant functional groups (FGN) and assessed corresponding changes in testate amoebae communities. The number of plant species was kept constant. When FGN was increased from 1 to 3, species number and total community density of live testate amoebae were enhanced according to a linear and a saturating function, respectively. From FGN 1 to 2, the appearance of new testate amoebae species did not affect the presence of the resident species, whereas, from FGN 2 to 3 about one quarter of the resident testate amoebae species was replaced, without altering the total species number. Overall, density by species increased, while evenness of the testate amoebae community was not affected by FGN; although Trinema lineare, one of the most common species, became more abundant. The observed relationship between plant functional group diversity and testate amoebae diversity could shed new light on the biogeographical distribution patterns of protists.

A model of biocomplexity and its application to the analysis of some terrestrial and marsh eukaryotic microbial communities with an emphasis on amoeboid protists

Biocomplexity theory has become increasingly important in understanding ecosystem dynamics as we realize that the interactions among subunits in a multi-component system often produce elaborate states that are not easily explained in terms of the individual parts of the system. A Euclidean geometric model of biocomplexity is presented and illustrated using protistan communities. The model is based on three quantitative biotic dimensions (indices) for small subsamples (0.01 g) taken from each sample core of substratum: (1) richness of morphospecies expressed as mean count per 0.01 g, (2) spatial diversity of protists expressed as then umber of unique morphospecies (i.e. those occurring in only one of the 0.01-g subsamples and not in any of the other subsamples), and (3) patchiness (non-uniform aggregation) of the distribution of protists across the 0.01-g subsamples. These three indices are mapped into a three-dimensional Euclidean space model, and the position of each point and its geometric distance from the origin are used as a general index of biocomplexity. The usefulness of the model is illustrated by applying it to a range of terrestrial and marsh communities. Within the set of 15 samples examined in this study, the marsh rhizosphere samples are among the most complex.

Density and diversity of protozoa in some arid Australian soils

This is the first extensive study of soil protozoa of arid lands. Twenty-six samples from litters, soils, termitaria, and a cyanobacterial crust, collected from central and south Australian arid lands, were analyzed for numbers and species of gymnamoebae, ciliates, and testacea. Amoebae ranged from 1,000-5,000/g of material, and were two orders of magnitude more abundant than ciliates. Both groups increased in abundance and species richness from bare soils through spinifex to mulga to chenopod vegetations. Testacea ranged 900-5,000/g with similar species richness throughout vegetations, but reached 11,900/g with a doubling of species in a refugium in Kings Canyon. The most prevalent species of amoebae, ciliates, and testacea were taxa associated with ephemeral and disturbed habitats (r-selection). The cyanobacterial crust might be considered a micro-refugium because it contained a number of non-encysting protozoa, including Thecamoeba sp. and Nassula picta, feeding on cyanobacterial filaments. The numbers and species richness of protozoa under shrubs were greater than in bare soils, supporting the resource island hypothesis that desert plants create soil heterogeneity by localizing soil fertility under their canopies.

Cultivation of pathogenic and opportunistic free-living amebas

Free-living amebas are widely distributed in soil and water, particularly members of the genera Acanthamoeba and NAEGLERIA: Since the early 1960s, they have been recognized as opportunistic human pathogens, capable of causing infections of the central nervous system (CNS) in both immunocompetent and immunocompromised hosts. Naegleria is the causal agent of a fulminant CNS condition, primary amebic meningoencephalitis; Acanthamoeba is responsible for a more chronic and insidious infection of the CNS termed granulomatous amebic encephalitis, as well as amebic keratitis. Balamuthia sp. has been recognized in the past decade as another ameba implicated in CNS infections. Cultivation of these organisms in vitro provides the basis for a better understanding of the biology of these amebas, as well as an important means of isolating and identifying them from clinical samples. Naegleria and Acanthamoeba can be cultured axenically in cell-free media or on tissue culture cells as feeder layers and in cultures with bacteria as a food source. Balamuthia, which has yet to be isolated from the environment, will not grow on bacteria. Instead, it requires tissue culture cells as feeder layers or an enriched cell-free medium. The recent identification of another ameba, Sappinia diploidea, suggests that other free-living forms may also be involved as causal agents of human infections.

Dynamics of protozoan and metazoan communities in a full scale wastewater treatment plant by rotating biological contactors

Performance of a full-scale wastewater treatment plant by rotating biological contactors (RBC) system was monitored during a year by physico-chemical and microbial characterisation. Six points along wastewater treatment were selected in the plant: three points along the water line (influent, sedimentation tank and effluent) and three points along RBC system (RBC1, RBC2 and RBC3). Although a large seasonal change in the values of physico-chemical parameters was observed, operation of the plant was optimal during all year (90% of removal in BOD5 and SS influent content). Microbial characterisation was approached by determining the structure and dynamics of protozoan and metazoan communities. Protozoa were the most abundant in all stages in the plant, heterotrophic flagellates being the most representative group in the water line and ciliates in the RBC system. The same seasonal preference was only observed for heterotrophic flagellates in the water line and green flagellates in the RBC system, both groups having highest abundances in summer and spring, respectively. Identification of ciliated protozoa populations rendered 58 species of ciliates in the plant. Most of these species are typical of aerobic wastewater treatment systems except three of them, which are cited for the first time in this type of ecosystems: Chaenea stricta, Holosticha mancoidea and Oxytricha lanceolata. Along the water line 34 species were identified, and half of them only appeared occasionally (once in all the study), while along the RBC system biofilms 55 species were observed, and the majority appeared permanently in this system. Our results indicate that the type of habitat, rather than the physico-chemical water parameters, was the primary factor in determining the different distribution of protozoan and metazoan communities in the plant. In RBC biofilms, the structure of ciliate protozoa community was found to be quite sensitive to changes in physico-chemical parameters, mainly to organic loading (BOD5) variations.

Weightlessness experiments on Biosatellite II

Four experiments in the aft compartment of Biosatellite II investigated the broad question of the effect of nearly zero gravity on the development, morphology and metabolism of plants and animals. The fertilization and development of the egg of a vertebrate (the frog, Rana pipiens), the feeding and growth of a protozoan (the giant amoeba, Pelomyxa carolinensis), the orientation of leaves and petioles of a young dicotyledon (pepper plants, Capsicum annuum) and the morphogenesis, orientation, histochemistry and biochemistry of a monocotyledon seedling (wheat, Triticum vulgare) gave a broad scope. All are known to have specific responses to normal gravity and changes in them might be expected to reflect the effects of orbital flight on living organisms. No differences in development of the frog eggs could be detected. Unfortunately, the 3 1/2 hour delay in launch allowed the first cleavage (the stage most sensitive to inversion) to appear before launch. Although the orbited embryos were somewhat slower to reach certain stages of development, recovered embryos developed just as did the controls. The amoebae fed normally while in orbit, and specimens fixed in orbit retained the ordinary heteropodal shape. Growth rates of orbited amoebae, both fed and starved, were slower than controls following reentry and recovery procedures. In continuous-fed organisms there was little or no effect of flight detectable in growth rate or actual number of divisions. Electron micrographs showed no abnormalities and few differences between flight and control organisms. The pepper plants were photographed in orbit at ten-minute intervals, as were the clinostat and erect controls. The subsequent measurement of photographs showed that in the orbited plants all leaves showed epinasty, the interaxial angle decreasing by 20-60 degrees C. Plants on the horizontal clinostat behaved comparably, but recovered more rapidly than orbited plants when returned to the normal erect position. Although the maximum age of wheat seedlings was only 65 hours, coleoptile and root growth rates during that time had not been significantly altered by flight or by slow rotation on a horizontal clinostat. There was some evidence that growth was accelerated after normal gravity was restored. The orientation of coleoptiles and of primary and lateral roots of orbited plants varied significantly from the normal erect seedlings but was almost identical with that of clinostat plants. The Periodic-Acid-Schiff technique on sectioned material showed starch grains at the bottom of cells of erect control coleoptile and root tips, while in orbited and clinostated plants the grains were located more or less at random. Histochemical differences between clinostat and orbited tissues are apparent however. Peroxidase localization varied and its activity was higher in both clinostat and orbited tissues; five other enzymes studied biochemically showed no differences. These experiments all suggest that there is no deleterious effect on living organisms or their activities from short-term weightlessness. Several results indicate that the horizontal clinostat may simulate the weightless state effectively here on Earth.

Free-living amoebae promote growth and survival of Helicobacter pylori

Transmission routes of Helicobacter pylori remain poorly understood. The finding of bacterial DNA in water suggests the involvement of environmental factors. Here we report successful co-cultivation of H. pylori with Acanthamoeba castellanii, which circumvents the requirement of this bacterium for precise microaerobic conditions and a large supply of nutrients in order to grow. H. pylori was able to propagate and remain viable for several weeks in the presence of amoebae under experimental conditions. Intact, metabolically active bacteria could be demonstrated in vacuoles. The putative dependence of H. pylori on free-living amoebae in nature could be important with respect to transmission and prevalence, as shown for some other pathogenic bacteria.

Effects of bacteria on the growth of an amoeba infecting the gills of turbot

We analysed the influence of various bacteria on the in vitro growth of trophozoites of a Platyamoeba strain isolated from diseased gill tissues of cultured turbot. Little or no growth was shown by amoebae cultured in the presence of (1) the turbot-pathogenic bacteria Vibrio anguillarum, Aeromonas salmonicida or Streptococcus sp., (2) Pasteurella piscicida or Vibrio vulnificus (pathogenic for some fishes but not turbot), or (3) the non-pathogenic 'environmental' bacteria Vibrio campbelli, Vibrio fluvialis or Pseudomonas dondorofii. The only bacteria which were successfully utilized as food sources were Aeromonas hydrophila (pathogenic for some fishes but not turbot) and the non-pathogens Vibrio natriegens, Pseudomonas nautica and Escherichia coli. These results suggest that the colonization of the gills of cultured turbot by the epizoic amoeba Platyamoeba may be an indicator of faecal contamination.

[Cell biology and life cycle of the testate amoeba Corythion delamarei]

Corythion delamarei Bonnet, Thomas, 1960, a typical testate amoeba with hyaline, filiform pseudopodia (Filosea Leidy, 1879), is a mass and widely spread species in the forest soil of Leningrad district. This species has been studied in natural and experimental conditions by means of morphological, cytochemical and morphometrical methods, including original culturing in vitro. The complex life cycle of C. delamarei involves the number of phases: trophozoites, precysts, resting cysts, copulating trophozoits, cystozygotes, cells with spores inside the shell, small amoeboid cells producing spores after germination. Different stages display structural peculiarities reflecting adaptation to exogenous environment. In C. delamarei sexual process has been first discovered. It represents a primitive form of isogamic copulation of morphologically similar trophozoites copulation and results in uninuclear cystozygote formation. The zygote nucleus is a synkaryon meiosis is zygotic, and is accomplished in two steps. Copulation occurs only between two trophozoites of one and the same species. Further zygote development includes its excystation that eventually gives rise to a trophozoite which then undergoes several metagamic divisions resulting in spore formation, thus starting a new generation of trophozoites.

Interaction of actin filaments with the plasma membrane in Amoeba proteus: studies using a cell model and isolated plasma membrane

We prepared a cell model of Amoeba proteus by mechanical bursting to study the interaction between actin filaments (AFs) and plasma membrane (PM). The cell model prepared in the absence of Ca2+ showed remarkable contraction upon addition of ATP. When the model was prepared in the presence of Ca2+, the cytoplasmic granules formed an aggregate in the central region, having moved away from PM. Although this model showed contraction upon addition of ATP in the presence of Ca2+, less contraction was noted. Staining with rhodamine-phalloidin revealed association of AFs with PM in the former model, and a lesser amount of association in the latter model. The interaction between AFs and PM was also studied using the isolated PM. AFs were associated with PM isolated in the absence of Ca2+, but were not when Ca2+ was present. These results suggest that the interaction between AFs and PM is regulated by Ca2+.

Microbiologic analysis of bottled water: is it safe for use with contact lenses?

OBJECTIVE

To analyze commercially available bottled water as a possible source of microbial contamination of contact lenses.

METHODS

Two different lots of 23 brands of noncarbonated bottled water were tested for coliforms, total bacteria, fungi, and free-living amebae. A sample consisted of three separate 100-ml aliquots from one lot of each brand (46 samples). Aliquots were vacuum-filtered using a 0.45-microm Nalgene analytical filter unit, and the membrane filter was placed on a filter pad in a Petri dish containing test medium. Plates were examined under a stereomicroscope, and the number of colony-forming units (CFUs) was calculated for each sample. To test for the presence of free-living amebae, three aliquots totaling approximately 3800 ml were concentrated using 8-microm filters, and the filters were placed on non-nutrient agar with live Enterobacter aerogenes. To assess the possibility of contaminating contact lenses, etafilcon lenses were rinsed in 2-ml aliquots of four brands of bottled water and then cultured.

RESULTS

Seventeen (37%) of 46 samples, representing 11 (48%) of 23 brands, contained viable micro-organisms. Bacteria, including coliforms, were recovered from 12 samples of 8 brands. Yeasts or molds were recovered from seven samples of five brands. Free-living amebae were isolated from two samples, and fresh-water algae were found in both samples of one brand. Nine (20%) of 46 samples, representing 7 (30%) of the 23 brands, had more than 500 CFUs per ml or contained coliforms. Sterile contact lenses became contaminated when exposed for 1 minute to two of four brands of water from which micro-organisms were recovered.

CONCLUSION

Some bottled waters contain high numbers of potential ocular pathogens. Bottled water is not safe for routine use with contact lenses.

Efficacy of novel antimicrobials against clinical isolates of opportunistic amebas

We examined the effects of the macrolide antimicrobial agent azithromycin and phenothiazine compounds against clinical isolates of Acanthamoeba spp. and Balamuthia mandrillaris, opportunistic pathogens of human beings and other animals. Acanthamoeba growth was inhibited in vitro at 1, 5, and 10 micrograms/ml of azithromycin, but not the macrolides, erythromycin, and clarithromycin. In experiments attempting to simulate in vivo conditions, azithromycin protected monolayers of rat glioma cells from destruction by Acanthamoeba at a concentration of 0.1 microgram/ml, and delayed destruction at concentrations of 0.001 and 0.01 microgram/ml. We concluded that the minimal inhibitory concentration of azithromycin was 0.1 microgram/ml. Our results, however, suggested that the drug was amebastatic but not amebicidal, since ameba growth eventually resumed after drug removal. The phenothiazines (chlorpromazine, chlorprothixene, and triflupromazine) inhibited Acanthamoeba growth by 70-90% at 5 and 10 micrograms/ml, but some of these compounds were toxic for rat glioma cells at 10 micrograms/ml. Azithromycin was not very effective against B. mandrillaris in an in vitro setting, but was amebastatic in tissue culture monolayers at concentrations of 0.1 microgram/ml and higher. Balamuthia amebas showed in vitro sensitivity to phenothiazines. Ameba growth was inhibited 30-45% at 5 micrograms/ml in vitro, but completely at 5 micrograms/ml in the rat glioma model. In spite of their potential as antiamebic drugs in Balamuthia infections, toxicity of phenothiazines limits their use in clinical settings.

Ultrastructure of the nucleus of the Iodamoeba bütschlii cyst

The ultrastructure of the Iodamoeba bütschlii cyst from human feces was studied. The glycogen mass appears as a compact dense body in the cytoplasm without any surrounding membrane. The cytoplasm has no mitochondrion. The nucleus shows a distinct nucleolus filled with electron-dense particles. On one side of the nucleolus are electron-dense cytoplasmic masses measuring 200-400 nm. The nuclear membrane is two-layered and shows pores.

[Patterns in the growth and functioning of single-cell organisms under conditions of altered gravitational force]

The results of studies over many years on various types of unicellular free-swimming organisms in conditions of altered gravity (hyper-, hypo-, and microgravity ranging from 10(-5) to 5 g) were reviewed. Laws governing their growth and functioning under these conditions were established. In general, gravisensing of unicellular free-swimming organisms depends on their metabolic activity and mobility, on the one hand, and on the environmental conditions of the population, on the other. A working hypothesis on the priority of ecophysiological properties (environment, metabolic activity, and mobility) over morphological properties (mass, dimensions, and shape) in receiving and processing of gravity stimuli at the cellular level has been formulated.

Fatal infections with Balamuthia mandrillaris (a free-living amoeba) in gorillas and other Old World primates

Balamuthia mandrillaris is a newly described free-living amoeba capable of causing fatal meningoencephalitis in humans and animals. Because the number of human cases is rapidly increasing, this infection is now considered an important emerging disease by the medical community. A retrospective review of the pathology database for the Zoological Society of San Diego (the San Diego Zoo and San Diego Wild Animal Park) for the period July 1965 through December 1994 revealed five cases of amoebic meningoencephalitis, all in Old World primates. The infected animals were a 3-year, 10-month-old female mandrill (Papio sphinx), from which the original isolation of B. mandrillaris was made, a 5-year-old male white-cheeked gibbon (Hylobates concolor leucogenys), a 1-year-old female western lowland gorilla (Gorilla gorilla gorilla), a 13-year, 5-month-old male western lowland gorilla, and a 6-year-old female Kikuyu colobus monkey (Colobus guereza kikuyuensis). Two different disease patterns were identified: the gibbon, mandrill, and 1-year-old gorilla had an acute to subacute necrotizing amoebic meningoencephalitis with a short clinical course, and the adult gorilla and colobus monkey had a granulomatous amoebic meningoencephalitis with extraneural fibrogranulomatous inflammatory lesions and a long clinical course. Indirect immunofluorescent staining of amoebas in brain sections with a Balamuthia-specific polyclonal antibody was positive in all five animals. Indirect immunofluorescent staining for several species of Acanthamoeba, Naegleria fowleri, and Hartmanella vermiformis was negative. Direct examination of water and soil samples from the gorilla and former mandrill enclosures revealed unidentified amoebas in 11/27 samples, but intraperitoneal inoculations in mice failed to induce disease. Attempts to isolate amoebas from frozen tissues from the adult male gorilla were unsuccessful.

Quantitation of free-living amoebae and bacterial populations in eyewash stations relative to flushing frequency

This study investigated the concentration of amoebic and bacterial populations in eyewash station water relative to various flushing regimens. Amoebae concentrations averaged approximately 200 amoebae/100 mL in 13 of 15 stations positive for amoebae and consisted of Hartmannella and Acanthamoeba. Bacterial concentrations ranged from 10(0) to more than 10(5) colony forming units per mL. Amoebic concentrations differed notably between stations located in Buildings X and Y (p < 0.0001). Further study indicated that removal of diffusing screens did not substantially change (p > 0.05) the concentration of amoeba. Amoebic and bacterial concentrations temporarily decreased with the various flushing regimens tested. Lower amoebic concentrations were not sustained by a weekly 3-minute or a monthly 1-minute flushing regimen. However, weekly 3-minute flushes appeared to be more effective in maintaining lowered bacterial concentrations (p < 0.0001).

Dictyopterin appears at amoebae emergence during spore germination in Dictyostelium

Intracellular dictyopterin, which is present in reduced form, mainly as tetrahydrodictyopterin, both in vegetative cells and in starved cells, could neither be detected in dormant spores nor in unswollen or swollen activated spores. Synthesis of tetrahydrodictyopterin starts with emergence of nascent amoebae during spore germination. Tetrahydrodictyopterin levels in cell-free extracts vary as a function of the percent emerged amoebae in spore suspension. These data are consistent with a requirement for tetrahydrodictyopterin during vegetative growth.

Axenic growth and drug sensitivity studies of Balamuthia mandrillaris, an agent of amebic meningoencephalitis in humans and other animals

A cell-free growth medium for the opportunistic pathogenic ameba Balamuthia mandrillaris is presented. This represents an advance over the use of monkey kidney cells for growth of the amebas and can be helpful in isolation of these amebas from brain tissue from cases in which amebic meningoencephalitis is a diagnostic possibility, as well as for biochemical and molecular biological studies. Three isolates of Balamuthia have been cultured in this medium. The cell-free growth system was also used to screen cultures for sensitivity to a variety of antimicrobial agents. Of the various drugs tested, pentamidine isethionate was most effective against amebas (ca. 90% inhibition after 6 days of exposure), but the drug was amebastatic and not amebacidal in the axenic system at the highest concentration tested (10 micrograms/ml).

Stimulatory effect of cooling tower biocides on amoebae

Two species of amoebae were isolated from the cooling tower of an air-conditioning system and examined for effects of exposure to four cooling tower biocides, a thiocarbamate compound, tributyltin neodecanoate mixed with quaternary ammonium compounds, another quaternary ammonium compound alone, and an isothiazolin derivative. The amoebae isolated were Acanthamoeba hatchetti and a Cochliopodium species. Two other amoeba cultures, an A. hatchetti culture and Cochliopodium bilimbosum, were obtained from the American Type Culture Collection (ATCC) and were also tested. The cooling tower isolates were more resistant to most of the biocides than the ATCC isolates were. The isothiazolin derivative was the least inhibitory to all four amoeba isolates, and tributyltin neodecanoate mixed with quaternary ammonium compounds was the most inhibitory to three of the four isolates. After exposure to lower concentrations of the biocides, including for one strain the manufacturer's recommended concentration of one biocide, the cooling tower amoeba populations increased significantly compared with unexposed controls, whereas the ATCC isolates were not stimulated at any of the concentrations tested. In some cases, concentrations which stimulated cooling tower amoebae inhibited the growth of the ATCC isolates. These results suggest that cooling tower amoebae may adapt to biocides, underscoring the need to use freshly isolated cooling tower organisms rather than organisms from culture collections for testing the efficacy of such biocides. The stimulatory effect of biocides on amoeba populations is an alarming observation, since these organisms may be reservoirs for legionellae. Biocides used to control microbial growth may actually enhance populations of host organisms for pathogenic bacteria.

Revival of Dobell's "chromidia" hypothesis: chromatin bodies in the amoebomastigote Paratetramitus jugosus

Multiple fission of a mature Paratetramitus jugosus (approx. 10 micrometers long) resulted in the production of many small, roughly spherical (2-7 micrometers in diameter) amoebae. Our observation of live material and examination of over two hundred micrographs lead us to suggest that DNA-containing membrane-bounded chromatin bodies bud amitotically from the nucleus. DAPI-stained bodies of these were observed in the cytoplasm of amoebae, mastigotes, and cysts, and at least some of these chromatin bodies seemed to be released into the medium. This interpretation revives for P. jugosus the "chromatin hypothesis" of Dobell. Our data, consistent with the descriptions of Dobell, Hogue, and Wherry, indicate that encysting amoebae may reproduce by chromidia. Dobell's original chromidia concept was limited to amoebae. Others claimed for it far-reaching consequences: "chromidia" were touted as an explanation for embryogenesis and histogenesis of metazoa. Although there is no evidence for chromidia in animals, outright rejection of Dobell's chromidia hypothesis sensu stricto as an amitotic multiple fission process in amoebae is unjustified.

Effect of thermal additions on the density and distribution of thermophilic amoebae and pathogenic Naegleria fowleri in a newly created cooling lake

Pathogenic Naegleria fowleri is the causative agent of fatal human amoebic meningoencephalitis. The protozoan is ubiquitous in nature, and its presence is enhanced by thermal additions. In this investigation, water and sediments from a newly created cooling lake were quantitatively analyzed for the presence of thermophilic amoebae, thermophilic Naegleria spp., and the pathogen Naegleria fowleri. During periods of thermal additions, the concentrations of thermophilic amoebae and thermophilic Naegleria spp. increased as much as 5 orders of magnitude, and the concentration of the pathogen N. fowleri increased as much as 2 orders of magnitude. Concentrations of amoebae returned to prior thermal perturbation levels within 30 to 60 days after cessation of thermal additions. Increases in the thermophilic amoeba concentrations were noted in Savannah River oxbows downriver from the Savannah River plant discharge streams as compared with oxbows upriver from the discharges. Concentrations of thermophilic amoebae and thermophilic Naegleria spp. correlated significantly with temperature and conductivity. Air samples taken proximal to the lake during periods of thermal addition showed no evidence of thermophilic Naegleria spp. Isoenzyme patterns of the N. fowleri isolated from the cooling lake were identical to patterns of N. fowleri isolated from other sites in the United States and Belgium.

A temporary flagellate (mastigote) stage in the vahlkampfiid amoeba Willaertia magna and its possible evolutionary significance

A temporary flagellate (mastigote) stage has been observed in several isolates of the vahlkampfiid amoeba Willaertia magna. In an Australian isolate studied in detail, flagellates appeared synchronously, although later than in Naegleria fowleri or N. lovaniensis under similar conditions (half-maximal time, t50 = 168 min at 37 degrees C). The flagellates initially have four flagella and lack a cytostome, but undergo several successive divisions, the first of them synchronous, resulting in progressive reduction in cell volume. New flagella appear during and after division, and the number of flagella in daughter cells of later divisions is rather variable. Comparison of these observations with descriptions of other amoeboflagellates confirms that Willaertia is a valid genus. A likely sequence of morphological changes in the evolution of Willaertia and Naegleria from a hypothetical ancestral vahlkampfiid is proposed.

Occurrence and parameters of frequency of Legionella in warm water systems of hospitals and hotels in Lower Saxony

A total of 1241 water samples was investigated from 103 hospitals and 62 hotels in Lower Saxony 1985-87. 331 of 949 samples from hospitals and 26 of 292 samples from hotels were Legionella positive. All together 70% of the hospitals and 18% of the hotels investigated were Legionella positive, and 836 strains of Legionella were isolated (Table 1). As they could be diagnosed they belong to L. pneumophila SG1 306 strains, SG2 36 strains, SG3 127 strains, SG4 45 strain, SG5 29 strain, SG6 106 strains, SG9 13 strains and SG10 13 strains. Further 134 strains belonging to L. pneumophila but not to SG1-SG12 show cross reactions with serogroups 5, 8, and 10. Finally, 16 strains belong to L. dumoffii and 1 strain to L. anisa (Table 2). The following parameters of water samples were studied, too: temperature, pH value, conductivity, concentration of iron, of organic matter, of other bacteria, occurrence of amoebas, and the materials of water plumbing systems. Most samples contained concentrations of Legionella in the range of 10(1)-10(3) CFU/ml, highest concentrations were 10(5) CFU/ml (Fig. 1). Most frequently, Legionella were isolated within the range of temperature of 35-45 degrees C. However, a few of the water samples were positive for Legionella even up to 66 degrees C (Fig. 3). The conductivity has no and the pH value (Fig. 2) has only little influence on the occurrence of Legionella. There is a positive correlation between concentration of iron and frequency of Legionella (Fig. 4). Also organic matter (Fig. 6) and amoebas (Table 3) seem to enhance the occurrence of Legionella. Plumbing systems consisting of copper showed an inhibitory effect on Legionella during the first five years, whereas no effect could be detected in older systems (Fig. 5).

Effect of essential amino acids on the phosphorylation of a 40S ribosomal protein and protein synthesis in Acanthamoeba castellanii

Reversible and multiple phosphorylation of a 40S ribosomal protein is observed in a variety of eukaryotic cells. In the primitive eukaryote Acanthamoeba, one or three phosphorylated S3 derivatives are observed during growth phase in nondefined nutrient medium (ND cells) or in chemically defined nutrient medium (D cells), respectively. In both cases, stationary phase cells exhibit nonphosphorylated S3; however, transfer of these cells into the respective fresh nutrient media results in a transient accumulation of four phosphorylated S3 derivatives. Transfer of D cells into nutrient medium, deficient in all or any single essential amino acids, leads to reversible inhibition of S3 phosphorylation and growth arrest. The low level of phosphorylated S3 is not simply the consequence of growth arrest, since in cells where growth is arrested differently, the level of phosphorylated S3 can be high. In response to amino acid deficiency, a number of other changes can be observed. These include a 2-3-fold decrease of total protein synthesis, 13 changes in the cellular protein pattern, and specific alterations in the ribosome absorbance profiles and in the distribution of poly-A+ RNA within subribosomal and ribosomal fractions. While the rate of total protein synthesis seems to be associated with the level of phosphorylated S3, the level of the synthesis of at least 10 of the particular proteins can be dissociated from the level of S3 phosphorylation.

Partial purification and characterization of Naegleria fowleri beta-glucosidase

Naegleria fowleri cells, grown axenically, contain high levels of beta-D-glucosidase which catalyzes the hydrolysis of 4-methylumbelliferyl-beta-D-glucopyranoside (4MUGlc) (Km, 0.9 mM), octyl-beta-D-glucoside (Km, 0.17 mM), and p-nitrophenyl-beta-D-glucopyranoside at relative rates of 1.00, 2.88, and 1.16, respectively (substrate concentration, 3.0 mM). When the amebae are subjected to freeze-thawing, sonication, and centrifugation (100,000 g, 1 h), 85% of the beta-glucosidase activity appears in the supernatant fraction. The beta-glucosidase was purified 40-fold (34% yield) using a combination of chromatographic steps involving DE-52 cellulose, concanavalin A-Sepharose, and hydroxylapatite followed by isoelectric focusing. The predominant soluble beta-D-galactosidase activity in the Naegleria extract copurifies with the beta-D-glucosidase; the two activities have the same isoelectric point (pI, 6.9), similar heat stabilities, are both inhibited by lactobionic acid (Ki, 0.40 mM), and exhibit optima at pH 4.5, indicating that they are probably the same enzyme. The Naegleria beta-D-glucosidase has an apparent molecular weight of 66,000, a Stokes radius of 25 A, and a sedimentation coefficient of 4.2S. The beta-glucosidase is not inhibited by conduritol beta-epoxide or galactosylsphingosine but is completely inhibited by 1.25 mM bromo conduritol beta-epoxide. The latter compound, when present in the growth medium, inhibits the growth of the organism and profoundly alters its ultrastructure, the main effect being the apparent inhibition of cytokinesis and the generation of multinucleate cells. The issue of the role of the beta-glucosidase in the metabolism of the ameba and its possible role in pathogenic mechanisms are discussed.

Seasonal distribution of thermotolerant free-living amoebae. II. Lake Issaqueena

A quantitative study of the seasonal distribution of thermotolerant (37 degrees C and 45 degrees C), small free-living amoebae (FLA) was conducted in Lake Issaqueena, a warm, monomictic lake with steep, sloping banks and a maximum basin depth of 10 m in the Piedmont region of South Carolina. Naegleria and Vahlkampfia were the most frequently encountered FLA in littoral sediment and surface water samples whereas Acanthamoeba was most commonly isolated from profundal sediment, especially during late summer. In the water column, FLA populations were highest in a persistent detrital layer; however, few amoebae were isolated from a massive (approximately 1.5 m thick) layer of Oscillatoria. The only N. fowleri isolated in this study was from the detrital layer. Discussion of the influence of differences in watershed and basin morphology on variations in the size and generic composition of FLA populations for the aquatic ecosystems of Lake Issaqueena and Willard's Pond is included.

Buoyant density variation during the cell cycle in microorganisms

The behavior of cell buoyant density during the cell cycle has been determined for a number of different cell types, including bacteria, yeast, and mammalian cells. Mean buoyant density was extremely constant and independent of cell age during the cell cycle of the bacterium Escherichia coli, the fission yeast Schizosaccharomyces cerevisiae, the protozoan Amoebae proteus, cells from suspension cell cultures of mouse lymphoma and myeloma, and Chinese hamster ovary cells. In all of these cases, the buoyant densities of these cells were very narrowly distributed, with coefficients of variation of 0.1 to 0.3%. In contrast, buoyant density was variable in cells with thick cell walls and high buoyant densities. Density varied markedly during the cell cycle of the budding yeast Schizosaccharomyces cerevisiae and of the bacterium Streptococcus faecium. The average buoyant densities of cells in exponentially growing cultures of E. coli or Schizosaccharomyces pombe were also independent of growth rate of the cultures. Experiments with E. coli have established that cell buoyant density is controlled by the osmoregulatory system. Although the regulatory mechanisms for this control are unknown, the results suggest that the same or similar mechanisms regulate buoyant density in all of the cells that do not have unduly heavy cell walls and, therefore, these regulatory mechanisms were either conserved during evolution or reflect the convergent evolution found for organic osmolytes.

Ultrastructure of the amoebo-flagellate Protonaegleria westphali

Investigation of the ultrastructure of Protonaegleria westphali has been carried out by means of scanning electron microscopy (SEM) and transmission electronmicroscopy (TEM). SEM investigation demonstrated much enlarged trophozoites, flagellates and cysts corresponding to those under light microscopical observation. In situ fixation of moving trophozoites revealed attachment to the substratum by many uroidal and lateral filopodia. The typical flagellate stage has four flagella inserted two by two at the anterior pole of the cell. The smooth wall of cysts had prominent pores sealed by a mucous plug. Apart from their greater size, trophozoites and cysts resemble those of the genus Naegleria. Mitochondria are not as elongated as in the case of Naegleria; rather, they are round. The cyst is surrounded by a thick, layered endocyst (0.2-0.5 micron) and a delicate ecotcyst loosely apposed to the endocyst. Both walls join at the region of the prominent pores, forming a characteristically thick collar. This, together with the pore structure (up to 1.0 micron in diameter) places the amoeba in group I of N. gruberi, according to Pussard and Pons (1979). The flagellate state usually has four flagella which are anchored firmly by a prominent flagellar apparatus or mastigont at the anterior pole of the cell, comparable to that of the genus Tetramitus. The flagella show a typical 9 + 2 arrangement of microtubules (MT) and are surrounded by a sheath which is continuous with the cell membrane. Main elements of the mastigont could be demonstrated as typical kinetosomes of 0.75 micron length. Each is closely associated with the cross-striated rhizoplast located perpendicular to it.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and identification of 1(3),2-diacylglyceryl-(3)-O-4'-(N,N,N-trimethyl)homoserine from the soil amoeba, Acanthamoeba castellanii

A polar lipid accounting for 12.5% of the total lipid nitrogen has been isolated from the protozoan Acanthamoeba castellanii. On the basis of thin-layer chromatography and mass spectral analysis, the lipid has been identified as diacylglyceryltrimethylhomoserine (DGTS). Fast atom bombardment (FAB) mass spectra of DGTS are reported for the first time and are compared to the FAB mass spectra of phosphatidylcholines and the electron ionization (EI) and field desorption (FD) mass spectra of DGTS. Gas-liquid chromatographic-mass spectrometric (GLC-MS) analysis of the acyl chain composition of this lipid has shown that 87.5% consists of cis-9-octadecenoic acid. Plasma membrane isolated from this organism has shown that labeled DGTS appears in the plasma membrane but is not enriched in this fraction. DGTS has been isolated previously only from a limited number of green plants and one species of fungus. Identification of this lipid in Acanthamoeba indicates that this lipid is distributed among a diverse group of lower eucaryotes.

Conditions for maximum enflagellation in Naegleria fowleri

Ameba to flagellate transformation in Naegleria fowleri (Lovell strain) was affected by growth temperature, phase of growth, strain of ameba, culture agitation, enflagellation temperature, enflagellation diluent, and cell concentration. Amebae transformed best when they were grown without agitation and enflagellated with agitation. Regardless of growth temperature (23 degrees, 30 degrees, 37 degrees, and 42 degrees C were tested), amebae transformed best at 37 degrees C. Enflagellation was greatest for cells harvested between 24 h (mid-exponential) and 84 h (late stationary) of growth.

Naegleria fowleri and N. lovaniensis: differences in sensitivity to trimethoprim and other antifolates

The growth of Naegleria fowleri cultures in a BCS medium was not affected either by trimethoprim at 400 micrograms/ml or by aminopterine, 3,5-diaminopterine and methotrexate at 500 micrograms/ml. N. lovaniensis propagation in the same medium was inhibited with 10 micrograms/ml of trimethoprim, 50 micrograms/ml methotrexate and 100 micrograms/ml 3,5-diaminopteridine. Aminopterine was ineffective at a concentration of 500 micrograms/ml. The inhibitory effect of trimethoprim on N. lovaniensis cultures depended on the medium composition and could be neutralized by an addition of folic or tetrahydrofolic acids and a suspension of heat-killed Enterobacter aerogenes. Thymine, thymidine, hypoxantine and 2-amino-4-hydroxy-6-(tetrahydroxybutyl)-pteridine did not have an adverse effect. Trimethoprim activity in N. fowleri cultures could not be enhanced by the addition of Triton X-100 and Polymyxine B. Cryolyzate of N. fowleri amoebae did not influence the trimethoprim inhibition of N. lovaniensis cultures. Deviation in dihydrofolatereductase chemical structure or thymine dependency seems to be the probable explanation for N. fowleri antifolate resistance.

A light and electron microscopical study of a new, polymorphic free-living amoeba, Phreatamoeba balamuthi n. g., n. sp

A new amoeba, isolated from well water in Gambia, West Africa, is described and named Phreatamoeba balamuthi n. g., n. sp. Requiring anaerobic conditions for growth, it is easily cultured monoxenically with Escherichia coli or axenically in complex, undefined organic media. Three phenotypes have been observed in the life cycle: an amoeba, a flagellate, and a cyst. The amoeba moves by monopodia, is predominantly multinucleate, and varies from 11 to 160 microns in length. The flagellate has a single flagellum and is from 6 to 50 microns long. The cyst is surrounded by a resistant wall that lacks pores and ranges from 9 to 18 microns in diameter. The transformation from amoeba to flagellate can be induced nutritionally, the exact inducing factor(s) being unknown. Sexual reproduction has not been observed.

Seasonal distribution of thermotolerant free-living amoebae. I. Willard's Pond

A quantitative study of the seasonal distribution of thermotolerant (37 degrees C and 45 degrees C), small free-living amoebae (FLA) was conducted in Willard's Pond, a warm, monomictic lake in the Piedmont region of South Carolina. Correlation of physical and chemical parameters with the seasonal distribution was facilitated by partitioning the aquatic ecosystem into benthic, planktonic, and neustonic habitats. Population densities of FLA peaked in late summer in each habitat; however, species composition varied between habitats. Littoral sediment appeared to be the major habitat for FLA, with peaks in populations of Acanthamoeba and Naegleria in August, Hartmannella in July, and Vahlkampfia in May. Populations in profundal sediment underwent dramatic seasonal shifts, apparently in response to the seasonal chemical changes in the hypolimnion. Acanthamoeba was most prevalent in late summer, representing as much as 82% of the FLA in profundal sediment. Distribution patterns and species composition of FLA from surface water were similar to those from littoral sediment; however, a greater percentage of Naegleria was found in surface water. Numerous FLA were isolated from the neustonic community (surface film), and the number of FLA isolated in the surface film at the deep water station was found to be significantly (P less than 0.05) greater than the number from subsurface (5-10 cm) samples. In the water column, FLA populations consistently were highest in the detrital layer, which persisted at a depth of 3.0-3.4 m throughout the summer period. The large percentage of Naegleria contributing to FLA in the detrital layer suggests that Naegleria amoeboflagellates sink through the layer, flagellate, and swim back up, such migrations possibly being triggered by a reduction of nutrients below the layer or by the presence of anoxic, reducing conditions in the hypolimnion. In addition, weather events were found to play a major role in the redistribution of FLA between various habitats in the aquatic ecosystem, with such changes probably due to resuspension of FLA from littoral sediment by wind action and input from the watershed via runoff.

Study of an amoeboflagellate isolated from the nasal mucosa of man

This paper examines the biology, morphology, and pathogenicity for mice of an amoeboflagellate isolated from human nasal mucosa. The biological and morphological relationships of this isolate with the amoebae (Lobosea) and the true slime molds (Eumycetoza) are discussed though the taxonomic affinities of the organism have not been determined.

[Free-living amoeba in the human intestine. Evidences of parasitism]

Foram cultivadas fezes de 620 indivíduos para a pesquisa de amebas de vida livre, sendo 514 pacientes do Hospital Universitário Pedro Ernesto (UERJ) e 106 crianças e adultos de um orfanato. Foram positivas 70 amostras (11,2%) sendo 55 provenientes de pacientes do HU-UERJ e 15 de internos do orfanato. Foram isoladas 60 amostras de Acanthamoeba, 6 de Vahlkampfia, 5 de Hartmannella e 1 Echinamoeba. Alguns indivíduos tiveram cultura de fezes repetidamente positiva para Acanthamoeba durante dois meses de observação. Das amostras de Acanthamoeba isoladas, 28 foram inoculadas em camundongos por via intranasal, tendo sido reisoladas 16 (57,1%) amostras à partir de cérebro e (ou) pulmões dos animais. O estudo histopatológico demonstrou processo inflamatório agudo com presença de polimorfonucleares e amebas no cérebro e pulmões de alguns animais. O encontro de amostras patogênicas em fezes humanas reforça a hipótese do eventual desenvolvimento, em indivíduos portadores, de meningoencefalite amebiana granulomatosa, como infecção oportunística de origem endógena.

Amebostomes of Naegleria fowleri

The strain of ameba, culture incubation temperature, and phase of ameba growth affected the number of amebostomes present on amebae of Naegleria fowleri. Serial passage of N. fowleri through mice decreased the average number of amebostomes. Amebostomes were shown to be functional by their ability to engulf yeast cells.