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Gilbert Greub - One of the best experts on this subject based on the ideXlab platform.
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predator or prey chlamydophila abortus infections of a free living Amoebae acanthAmoeba castellani 9gu
Microbes and Infection, 2008Co-Authors: Mirjam Wirz, Adam Polkinghorne, Claudia Dumrese, Urs Ziegler, Gilbert Greub, Andreas Pospischil, Lloyd VaughanAbstract:Limited evidence exists to suggest that the ability to invade and escape protozoan host cell bactericidal activity extends to members of the Chlamydiaceae, intracellular pathogens of humans and animals and evolutionary descendants of Amoeba-resisting Chlamydia-like organisms. PCR and microscopic analyses of Chlamydophila abortus infections of AcanthAmoeba castellani revealed uptake of this chlamydial pathogen but, unlike the well-described inhabitant of A. castellani, Parachlamydia acanthAmoebae, Cp. abortus did not appear to propagate and is likely digested by its Amoebal host. These data raise doubts about the ability of free-living Amoebae to serve as hosts and vectors of pathogenic members of the Chlamydiaceae but reveal opportunities, via comparative genomics, to understand virulence mechanisms used by Chlamydia-like organisms to avoid Amoebal digestion.
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Biodiversity of Amoebae and Amoebae-resisting bacteria in a drinking water treatment plant
Environmental Microbiology, 2008Co-Authors: Vincent Thomas, Michel Jousset, Jean François Loret, Gilbert GreubAbstract:The complex ecology of free-living Amoebae (FLA) and their role in spreading pathogenic microorganisms through water systems have recently raised considerable interest. In this study, we investigated the presence of FLA and Amoebae-resisting bacteria (ARB) at various stages of a drinking water plant fed with river water. We isolated various Amoebal species from the river and from several points within the plant, mostly at early steps of water treatment. EchinAmoeba- and Hartmannella-related Amoebae were mainly recovered in the drinking water plant whereas AcanthAmoeba- and Naegleria-related Amoebae were recovered from the river water and the sand filtration units. Some FLA isolates were recovered immediately after the ozonation step, thus suggesting resistance of these microorganisms to this disinfection procedure. A bacterial isolate related to Mycobacterium mucogenicum was recovered from an EchinAmoeba-related Amoeba isolated from ozone-treated water. Various other ARB were recovered using co-culture with axenic AcanthAmoeba castellanii, including mycobacteria, legionella, Chlamydia-like organisms and various proteobacteria. Noteworthy, a new Parachlamydia acanthAmoebae strain was recovered from river water and from granular activated carbon (GAC) biofilm. As Amoebae mainly multiply in sand and GAC filters, optimization of filter backwash procedures probably offers a possibility to better control these protists and the risk associated with their intracellular hosts.
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the neff strain of acanthAmoeba castellanii a tool for testing the virulence of mycobacterium kansasii
Research in Microbiology, 2007Co-Authors: Genevieve Goy, Vincent Thomas, Katia Rimann, Katia Jaton, Guy Prodhom, Gilbert GreubAbstract:Virulent Mycobacterium kansasii (mainly subtype 1) may cause lung infections, whereas certain other strains (essentially subtype 3) are commonly non-pathogenic mycobacteria colonizing the human lower respiratory tract of patients. Determining the clinical significance of a strain isolated from a respiratory sample represents a major challenge for clinicians. Since some mycobacteria may use free-living Amoebae as a training ground to select virulence traits, we wondered whether the AcanthAmoeba castellanii Amoeba could be used to determine the virulence of these intracellular bacteria. We investigated whether the growth and cytopathic effect of M. kansasii in A. castellanii correlate with the virulence of M. kansasii determined clinically and by subtyping. Pathogenic subtype 1 M. kansasii strains grew better in A. castellanii than non-pathogenic subtype 3 strains when considering both the number of bacteria per Amoeba and the percentage of infected Amoebae. Moreover, a subtype 3 M. kansasii strain isolated from blood culture, and thus considered pathogenic, was revealed to grow in A. castellanii similarly to pathogenic subtype 1 strains. These results suggest that Amoebae may represent useful tools for testing the virulence of intracellular mycobacteria and other Amoeba-resisting bacteria. This is important, since identification of novel bacterial virulence factors relies largely on in vitro assessment of virulence.
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Biodiversity of Amoebae and Amoeba-resisting bacteria in a hospital water network
Applied and Environmental Microbiology, 2006Co-Authors: Vincent Thomas, Katia Herrera-rimann, Dominique S. Blanc, Gilbert GreubAbstract:Free-living Amoebae (FLA) are ubiquitous organisms that have been isolated from various domestic water systems, such as cooling towers and hospital water networks. In addition to their own pathogenicity, FLA can also act as Trojan horses and be naturally infected with Amoeba-resisting bacteria (ARB) that may be involved in human infections, such as pneumonia. We investigated the biodiversity of bacteria and their Amoebal hosts in a hospital water network. Using Amoebal enrichment on nonnutrient agar, we isolated 15 protist strains from 200 (7.5%) samples. One thermotolerant Hartmannella vermiformis isolate harbored both Legionella pneumophila and Bradyrhizobium japonicum. By using Amoebal coculture with axenic AcanthAmoeba castellanii as the cellular background, we recovered at least one ARB from 45.5% of the samples. Four new ARB isolates were recovered by culture, and one of these isolates was widely present in the water network. Alphaproteobacteria (such as Rhodoplanes, Methylobacterium, Bradyrhizobium, Afipia, and Bosea) were recovered from 30.5% of the samples, mycobacteria (Mycobacterium gordonae, Mycobacterium kansasii, and Mycobacterium xenopi) were recovered from 20.5% of the samples, and Gammaproteobacteria (Legionella) were recovered from 5.5% of the samples. No Chlamydia or Chlamydia-like organisms were recovered by Amoebal coculture or detected by PCR. The observed strong association between the presence of Amoebae and the presence of Legionella (P < 0.001) and mycobacteria (P = 0.009) further suggests that FLA are a reservoir for these ARB and underlines the importance of considering Amoebae when water control measures are designed.
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microorganisms resistant to free living Amoebae
Clinical Microbiology Reviews, 2004Co-Authors: Gilbert GreubAbstract: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.
Yann Héchard - One of the best experts on this subject based on the ideXlab platform.
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Environmental Mycobacterium avium subsp. paratuberculosis Hosted by Free-Living Amoebae
Frontiers in Cellular and Infection Microbiology, 2018Co-Authors: Ascel Samba-louaka, Etienne Robino, Thierry Cochard, Maxime Branger, Vincent Delafont, Willy Aucher, Wilfrid Wambeke, John Bannantine, Franck Biet, Yann HéchardAbstract:Mycobacterium avium subsp. paratuberculosis is responsible for paratuberculosis in animals. This disease, leading to an inflammation of the gastrointestinal tract, has a high impact on animal health and an important economic burden. The environmental life cycle of M. avium subsp. paratuberculosis is poorly understood and several studies suggest that free-living Amoebae (FLA) might be a potential environmental host. FLA are protozoa found in water and soil that are described as reservoirs of pathogenic and nonpathogenic bacteria in the environment. Indeed, bacteria able to survive within these Amoebae would survive phagocytosis from immune cells. In this study, we assessed the in vitro interactions between several strains of M. avium subsp. paratuberculosis and AcanthAmoeba castellanii. The results indicate that the bacteria were able to grow within the Amoeba and that they can survive for several days within their host. To explore the presence of M. avium subsp. paratuberculosis in environmental Amoebae, we sampled water from farms positive for paratuberculosis. A M. avium subsp. paratuberculosis strain was detected within an environmental Amoeba identified as related to the poorly described Rosculus genus. The bacterial strain was genotyped, showing that it was similar to previous infectious strains isolated from cattle. In conclusion, we described that various M. avium subsp. paratuberculosis strains were able to grow within Amoebae and that these bacteria could be found on farm within Amoebae isolated from the cattle environment. It validates that infected Amoebae might be a reservoir and vector for the transmission of M. avium subsp. paratuberculosis.
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Permissiveness of freshly isolated environmental strains of Amoebae for growth of Legionella pneumophila.
FEMS Microbiology Letters, 2016Co-Authors: Mathieu Dupuy, Pascaline Herbelin, Sylvie Soreau, Marie Binet, Celine Bouteleux, Yann HéchardAbstract:Legionella pneumophila is a pathogenic bacterium commonly found in water and responsible for severe pneumonia. Free-living Amoebae are protozoa also found in water, which feed on bacteria by phagocytosis. Under favorable conditions, some L. pneumophila are able to resist phagocytic digestion and even multiply within Amoebae. However, it is not clear whether L. pneumophila could infect at a same rate a large range of Amoebae or if there is some selectivity towards specific Amoebal genera or strains. Also, most studies have been performed using collection strains and not with freshly isolated strains. In our study, we assess the permissiveness of freshly isolated environmental strains of Amoebae, belonging to three common genera (i.e. AcanthAmoeba, Naegleria and VermAmoeba), for growth of L. pneumophila at three different temperatures. Our results indicated that all the tested strains of Amoebae were permissive to L. pneumophila Lens and that there was no significant difference between the strains. Intracellular proliferation was more efficient at a temperature of 40°C. In conclusion, our work suggests that, under favorable conditions, virulent strains of L. pneumophila could equally infect a large number of isolates of common freshwater Amoeba genera.
Arturo Casadevall - One of the best experts on this subject based on the ideXlab platform.
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Amoeba predation of cryptococcus neoformans results in pleiotropic changes to traits associated with virulence
Mbio, 2021Co-Authors: L C Liporagilopes, Jennifer L Tenor, John R Perfect, Christina A Cuomo, Samuel Dos R Santos, Arturo CasadevallAbstract:Amoeboid predators, such as Amoebae, are proposed to select for survival traits in soil microbes such as Cryptococcus neoformans; these traits can also function in animal virulence by defeating phagocytic immune cells, such as macrophages. Consistent with this notion, incubation of various fungal species with Amoebae enhanced their virulence, but the mechanisms involved are unknown. In this study, we exposed three strains of C. neoformans (1 clinical and 2 environmental) to predation by AcanthAmoeba castellanii for prolonged times and then analyzed surviving colonies phenotypically and genetically. Surviving colonies comprised cells that expressed either pseudohyphal or yeast phenotypes, which demonstrated variable expression of traits associated with virulence, such as capsule size, urease production, and melanization. Phenotypic changes were associated with aneuploidy and DNA sequence mutations in some Amoeba-passaged isolates, but not in others. Mutations in the gene encoding the oligopeptide transporter (CNAG_03013; OPT1) were observed among Amoeba-passaged isolates from each of the three strains. Isolates derived from environmental strains gained the capacity for enhanced macrophage toxicity after Amoeba selection and carried mutations on the CNAG_00570 gene encoding Pkr1 (AMP-dependent protein kinase regulator) but manifested reduced virulence in mice because they elicited more effective fungal-clearing immune responses. Our results indicate that C. neoformans survival under constant Amoeba predation involves the generation of strains expressing pleiotropic phenotypic and genetic changes. Given the myriad potential predators in soils, the diversity observed among Amoeba-selected strains suggests a bet-hedging strategy whereby variant diversity increases the likelihood that some will survive predation.IMPORTANCE Cryptococcus neoformans is a ubiquitous environmental fungus that is also a leading cause of fatal fungal infection in humans, especially among immunocompromised patients. A major question in the field is how an environmental yeast such as C. neoformans becomes a human pathogen when it has no need for an animal host in its life cycle. Previous studies showed that C. neoformans increases its pathogenicity after interacting with its environmental predator Amoebae. Amoebae, like macrophages, are phagocytic cells that are considered an environmental training ground for pathogens to resist macrophages, but the mechanism by which C. neoformans changes its virulence through interactions with protozoa is unknown. Our study indicates that fungal survival in the face of Amoeba predation is associated with the emergence of pleiotropic phenotypic and genomic changes that increase the chance of fungal survival, with this diversity suggesting a bet-hedging strategy to ensure that some forms survive.
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Amoeba predation of cryptococcus neoformans results in pleiotropic changes to traits associated with virulence
bioRxiv, 2020Co-Authors: L C Liporagilopes, S Dos R Santos, Jennifer L Tenor, John R Perfect, Christina A Cuomo, Arturo CasadevallAbstract:Phagocytic amoeboid predators such as Amoeba have been proposed to select for survival traits in soil microbes such as Cryptococcus neoformans that can also function in animal virulence by defeating phagocytic immune cells, such as macrophages. Several prior studies have shown that incubation of various fungal species with Amoeba can enhance their virulence. However, the mechanisms by which fungi adapt to Amoeba and thus change their virulence are unknown. In this study we exposed three strains of C. neoformans (1 clinical and 2 environmental) to predation by AcanthAmoeba castellanii for prolonged periods of time and then analyzed surviving colonies phenotypically and genetically. Surviving colonies were comprised of cells that expressed either pseudohyphal or yeast phenotypes, which demonstrated variable expression of such traits associated with virulence such as capsule size, urease production and melanization. Phenotypic changes were associated with aneuploidy and DNA sequence mutations in some Amoeba-passaged isolates, but not in others. Mutations in the gene encoding for the oligopeptide transporter (CNAG_03013; OPT1) were observed among Amoeba-passaged isolates from each of the three strains. In addition, isolates derived from environmental strains gained the capacity for enhanced macrophage toxicity after Amoeba selection and carried mutations on the CNAG_00570 gene, which encodes Pkr1 (AMP-dependent protein kinase regulator) but were less virulence in mice because they elicited more effective fungal-clearing immune responses. Our results indicate that C. neoformans survival under constant Amoeba predation involves the generation of strains expressing pleiotropic phenotypic and genetic changes, which confer increase resistance against protozoal predation. Given the myriad of potential predators in soils the diversity observed among Amoeba-selected strains suggests a bet-hedging strategy whereby variant diversity increases the likelihood that some will survive predation. Author summaryCryptococcus neoformans is a ubiquitous environmental fungus that is also a leading cause of fatal fungal infection in humans, especially among immunocompromised patients. Cryptococcosis is a worldwide concern due to its high mortality rate. A major question in the field is how an environmental yeast such as C. neoformans becomes a human pathogen when it has no need for animal host in its life cycle. Previous studies showed evidence that C. neoformans increases its pathogenicity after interacting with its environmental predator Amoebae. Amoebae behave like macrophages, an important immune cell in human body, so it is considered as a training ground for pathogens to resist macrophages. However, how C. neoformans changes its virulence through interacting with Amoebae is unknown. Here, we exposed C. neoformans to Amoebae for a long period of time. We found that C. neoformans cells recovered from Amoebae manifested numerous changes to phenotypes related to its virulence and one of the Amoeba-passaged C. neoformans cells had enhanced ability to kill macrophages. We further analyzed their genome sequences and found various mutations in different cells of Amoeba-passaged C. neoformans, showing that DNA mutations may be the major cause of the phenotypic changes after interacting with Amoebae. Our study indicates that fungal survival in the face of Amoeba predation is associated with the emergence of pleiotropic phenotypic and genomic changes that increase the chance of fungal survival.
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divalent metal cations potentiate the predatory capacity of Amoeba for cryptococcus neoformans
Applied and Environmental Microbiology, 2017Co-Authors: Arturo CasadevallAbstract:Among the best-studied interactions between soil phagocytic predators and a human-pathogenic fungus is that of AcanthAmoeba castellanii and Cryptococcus neoformans The experimental conditions used in Amoeba-fungus confrontation assays can have major effects on whether the fungus or the protozoan is ascendant in the interaction. In the presence of Mg2+ and Ca2+ in phosphate-buffered saline (PBS), C. neoformans was consistently killed when incubated with A. castellaniiA. castellanii survived better in the presence of Mg2+ and Ca2+, even when incubated with C. neoformans In the absence of Mg2+ and Ca2+, C. neoformans survived when incubated with A. castellanii, and the percentage of dead Amoebae was higher than when incubated without yeast cells. These results show that the presence of Mg2+ and Ca2+ can make a decisive contribution toward tilting the outcome of the interaction in favor of the Amoeba. Of the two metals, Mg2+ had a stronger effect than Ca2+ The cations enhanced A. castellanii activity against C. neoformans via enhanced phagocytosis, which is the major mechanism by which Amoebae kill fungal cells. We found no evidence that Amoebae use extracellular killing mechanisms in their interactions with C. neoformans In summary, the presence of Mg2+ and Ca2+ enhanced the cell adhesion on the surfaces and the motility of the Amoeba, thus increasing the chance for contact with C. neoformans and the frequency of phagocytosis. Our findings imply that the divalent cation concentration in soils could be an important variable for whether Amoebae can control C. neoformans in the environment.IMPORTANCE The grazing of soil organisms by phagocytic predators such as Amoebae is thought to select for traits that enable some of them to acquire the capacity for virulence in animals. Consequently, knowledge about the interactions between Amoebae and soil microbes, such as pathogenic fungi, is important for understanding how virulence can emerge. We show that the interaction between an Amoeba and the pathogenic fungus C. neoformans is influenced by the presence in the assay of magnesium and calcium, which potentiate Amoebae. The results may also have practical applications, since enriching soils with divalent cations may reduce C. neoformans numbers in contaminated soils.
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interaction of blastomyces dermatitidis sporothrix schenckii and histoplasma capsulatum with acanthAmoeba castellanii
Infection and Immunity, 2004Co-Authors: Judith N Steenbergen, Joshua D. Nosanchuk, Stephanie D Malliaris, Arturo CasadevallAbstract:Several dimorphic fungi are important human pathogens, but the origin and maintenance of virulence in these organisms is enigmatic, since an interaction with a mammalian host is not a requisite for fungal survival. Recently, Cryptococcus neoformans was shown to interact with macrophages, slime molds, and Amoebae in a similar manner, suggesting that fungal pathogenic strategies may arise from environmental interactions with phagocytic microorganisms. In this study, we examined the interactions of three dimorphic fungi with the soil Amoeba Acanthameobae castellanii. Yeast forms of Blastomyces dermatitidis, Sporothrix schenckii, and Histoplasma capsulatum were each ingested by Amoebae and macrophages, and phagocytosis of yeast cells resulted in Amoeba death and fungal growth. H. capsulatum conidia were also cytotoxic to Amoebae. For each fungal species, exposure of yeast cells to Amoebae resulted in an increase in hyphal cells. Exposure of an avirulent laboratory strain of H. capsulatum to A. castellanii selected for, or induced, a phenotype of H. capsulatum that caused a persistent murine lung infection. These results are consistent with the view that soil Amoebae may contribute to the selection and maintenance of certain traits in pathogenic dimorphic fungi that confer on these microbes the capacity for virulence in mammals.
An Chencai - One of the best experts on this subject based on the ideXlab platform.
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feeding characteristics of an Amoeba lobosea naegleria grazing upon cyanobacteria food selection ingestion and digestion progress
Microbial Ecology, 2006Co-Authors: Liu Xinyao, Shi Miao, Liao Yonghong, Gao Yin, Zhang Zhongkai, Wen Donghui, Wu Weizhong, An ChencaiAbstract:Bacterivory by heterotrophic nanoflagellates and ciliates has been widely studied in aquatic environments, but data on the grazing of Amoebae, are still scarce. From the water samples of Dianchi Lake (Kunming, Yunnan Province, China), we isolated an Amoeba, designated as Naegleria sp. strain W2, which had potent grazing effects on some kind of cyanobacteria. The food selection mechanism and the digestion process of the Amoeba were investigated in batch experiments. Predation experiments showed that filamentous cyanobacteria (e.g., Anabaena, Cylindrospermum, Gloeotrichia, and Phormidium) were readily consumed, with clearance rates ranging from 0.332 to 0.513 nL Amoeba−1 h−1. The tight threads (Oscilltoria) and aggregates (Aphanizomenon) could not be ingested; however, their sonicated fragments were observed inside food vacuoles, suggesting that their morphologies prevent them from being ingested. Live video microscopy noted that unicellular Chroococcaceae (e.g., Synechococcus, Aphanocapsa, and Microcystis) were excreted after ingestion, indicating that food selection takes place inside food vacuoles. To determine whether the tastes or the toxins prevented them from being digested, heat-killed cells were retested for predation. Digestion rates and ingestion rates of the Amoebae for filamentous cyanobacteria were estimated from food vacuole content volume. Through a “cold-chase” method, we found that the food vacuole contents declined exponentially in diluted Amoebae cells, and digestion rates were relatively constant, averaging about 1.5% food vacuole content min−1 at 28°C. Ingestion strongly depended on the satiation status of the Amoebae, starved Amoebae fed at higher rates compared with satiated Amoebae. Our results suggest that the food selection and food processing mechanisms of the Amoeba are similar to those of interception feeding flagellates; however, filamentous cyanobacteria cannot obtain a refuge under the grazing pressure of phagotrophic Amoebae, which may widen our knowledge on the grazing of protists.
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Feeding characteristics of an Amoeba (Lobosea : Naegleria) grazing upon cyanobacteria: Food selection, ingestion and digestion progress
microbial ecology, 2006Co-Authors: Liu Xinyao, Shi Miao, Liao Yonghong, Gao Yin, Zhang Zhongkai, Wen Donghui, Wu Weizhong, An ChencaiAbstract:Bacterivory by heterotrophic nanoflagellates and ciliates has been widely studied in aquatic environments, but data on the grazing of Amoebae, are still scarce. From the water samples of Dianchi Lake (Kunming, Yunnan Province, China), we isolated an Amoeba, designated as Naegleria sp. strain W2, which had potent grazing effects on some kind of cyanobacteria. The food selection mechanism and the digestion process of the Amoeba were investigated in batch experiments. Predation experiments showed that filamentous cyanobacteria (e.g., Anabaena, Cylindrospermum, Gloeotrichia, and Phormidium) were readily consumed, with clearance rates ranging from 0.332 to 0.513 nL Amoeba(-1) h(-1). The tight threads (Oscilltoria) and aggregates (Aphanizomenon) could not be ingested; however, their sonicated fragments were observed inside food vacuoles, suggesting that their morphologies prevent them from being ingested. Live video microscopy noted that unicellular Chroococcaceae (e.g., Synechococcus, Aphanocapsa, and Microcystis) were excreted after ingestion, indicating that food selection takes place inside food vacuoles. To determine whether the tastes or the toxins prevented them from being digested, heat-killed cells were retested for predation. Digestion rates and ingestion rates of the Amoebae for filamentous cyanobacteria were estimated from food vacuole content volume. Through a "cold-chase" method, we found that the food vacuole contents declined exponentially in diluted Amoebae cells, and digestion rates were relatively constant, averaging about 1.5% food vacuole content min(-1) at 28 degrees C. Ingestion strongly depended on the satiation status of the Amoebae, starved Amoebae fed at higher rates compared with satiated Amoebae. Our results suggest that the food selection and food processing mechanisms of the Amoeba are similar to those of interception feeding flagellates; however, filamentous cyanobacteria cannot obtain a refuge under the grazing pressure of phagotrophic Amoebae, which may widen our knowledge on the grazing of protists.EcologyMarine & Freshwater BiologyMicrobiologySCI(E)PubMed14ARTICLE3315-3255
Vincent Delafont - One of the best experts on this subject based on the ideXlab platform.
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VermAmoeba vermiformis: a Free-Living Amoeba of Interest
Microbial Ecology, 2018Co-Authors: Vincent Delafont, Marie-helene Rodier, Elodie Maisonneuve, Estelle CateauAbstract:Free-living Amoebae are protists that are widely distributed in the environment including water, soil, and air. Although the Amoebae of the genus AcanthAmoeba are still the most studied, other species, such as VermAmoeba vermiformis (formerly Hartmannella vermiformis ), are the subject of increased interest. Found in natural or man-made aquatic environments, V. vermiformis can support the multiplication of other microorganisms and is able to harbor and potentially protect pathogenic bacteria or viruses. This feature is to be noted because of the presence of this thermotolerant Amoeba in hospital water networks. As a consequence, this protist could be implicated in health concerns and be indirectly responsible for healthcare-related infections. This review highlights, among others, the consequences of V. vermiformis relationships with other microorganisms and shows that this free-living Amoeba species is therefore of interest for public health.
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Environmental Mycobacterium avium subsp. paratuberculosis Hosted by Free-Living Amoebae
Frontiers in Cellular and Infection Microbiology, 2018Co-Authors: Ascel Samba-louaka, Etienne Robino, Thierry Cochard, Maxime Branger, Vincent Delafont, Willy Aucher, Wilfrid Wambeke, John Bannantine, Franck Biet, Yann HéchardAbstract:Mycobacterium avium subsp. paratuberculosis is responsible for paratuberculosis in animals. This disease, leading to an inflammation of the gastrointestinal tract, has a high impact on animal health and an important economic burden. The environmental life cycle of M. avium subsp. paratuberculosis is poorly understood and several studies suggest that free-living Amoebae (FLA) might be a potential environmental host. FLA are protozoa found in water and soil that are described as reservoirs of pathogenic and nonpathogenic bacteria in the environment. Indeed, bacteria able to survive within these Amoebae would survive phagocytosis from immune cells. In this study, we assessed the in vitro interactions between several strains of M. avium subsp. paratuberculosis and AcanthAmoeba castellanii. The results indicate that the bacteria were able to grow within the Amoeba and that they can survive for several days within their host. To explore the presence of M. avium subsp. paratuberculosis in environmental Amoebae, we sampled water from farms positive for paratuberculosis. A M. avium subsp. paratuberculosis strain was detected within an environmental Amoeba identified as related to the poorly described Rosculus genus. The bacterial strain was genotyped, showing that it was similar to previous infectious strains isolated from cattle. In conclusion, we described that various M. avium subsp. paratuberculosis strains were able to grow within Amoebae and that these bacteria could be found on farm within Amoebae isolated from the cattle environment. It validates that infected Amoebae might be a reservoir and vector for the transmission of M. avium subsp. paratuberculosis.