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Annual Review of Pathology Jan 2020species are environmental gram-negative bacteria able to cause a severe form of pneumonia in humans known as Legionnaires' disease. Since the identification of in... (Review)
Review
species are environmental gram-negative bacteria able to cause a severe form of pneumonia in humans known as Legionnaires' disease. Since the identification of in 1977, four decades of research on biology and Legionnaires' disease have brought important insights into the biology of the bacteria and the molecular mechanisms that these intracellular pathogens use to cause disease in humans. Nowadays, species constitute a remarkable model of bacterial adaptation, with a genus genome shaped by their close coevolution with amoebae and an ability to exploit many hosts and signaling pathways through the secretion of a myriad of effector proteins, many of which have a eukaryotic origin. This review aims to discuss current knowledge of infection mechanisms and future research directions to be taken that might answer the many remaining open questions. This research will without a doubt be a terrific scientific journey worth taking.
Topics: Adaptation, Physiological; Amoeba; Eukaryotic Cells; Host-Pathogen Interactions; Humans; Legionella; Legionella pneumophila; Legionnaires' Disease
PubMed: 31657966
DOI: 10.1146/annurev-pathmechdis-012419-032742 -
FEMS Immunology and Medical Microbiology Jun 2007Among the many genera of free-living amoebae that exist in nature, members of only four genera have an association with human disease: Acanthamoeba spp., Balamuthia... (Review)
Review
Among the many genera of free-living amoebae that exist in nature, members of only four genera have an association with human disease: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri and Sappinia diploidea. Acanthamoeba spp. and B. mandrillaris are opportunistic pathogens causing infections of the central nervous system, lungs, sinuses and skin, mostly in immunocompromised humans. Balamuthia is also associated with disease in immunocompetent children, and Acanthamoeba spp. cause a sight-threatening infection, Acanthamoeba keratitis, mostly in contact-lens wearers. Of more than 30 species of Naegleria, only one species, N. fowleri, causes an acute and fulminating meningoencephalitis in immunocompetent children and young adults. In addition to human infections, Acanthamoeba, Balamuthia and Naegleria can cause central nervous system infections in animals. Because only one human case of encephalitis caused by Sappinia diploidea is known, generalizations about the organism as an agent of disease are premature. In this review we summarize what is known of these free-living amoebae, focusing on their biology, ecology, types of disease and diagnostic methods. We also discuss the clinical profiles, mechanisms of pathogenesis, pathophysiology, immunology, antimicrobial sensitivity and molecular characteristics of these amoebae.
Topics: Acanthamoeba; Amebiasis; Amoeba; Animals; Humans; Naegleria fowleri
PubMed: 17428307
DOI: 10.1111/j.1574-695X.2007.00232.x -
Applied and Environmental Microbiology Jan 2021Amoebae are protists that have complicated relationships with bacteria, covering the whole spectrum of symbiosis. Amoeba-bacterium interactions contribute to the study... (Review)
Review
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.
Topics: Amoeba; Bacteria; Bacterial Physiological Phenomena; Microbial Interactions
PubMed: 33158887
DOI: 10.1128/AEM.01866-20 -
Pathogens and Global Health Sep 2022Free-living amoebae (FLA) are considered environmental pathogens and thus pose a public health threat. Their ubiquity in natural sources may magnify the potential... (Review)
Review
Free-living amoebae (FLA) are considered environmental pathogens and thus pose a public health threat. Their ubiquity in natural sources may magnify the potential severity of health outcomes in the future. However, less attention was given despite several probable public health risks that arise from the presence of pathogenic strains in the environment. Here, we provide epidemiological data based on investigations involving the distribution and occurrence of free-living amoebae in the Republic of the Philippines. This aims to connect data of fragmented studies of these organisms and provide potential roadmaps in FLA research in the country. The majority of the reviewed articles (n = 19) focused on characterization studies (36.8%; 7/19) while environmental isolation and isolation from biological samples had an equal frequency of 31.6% (6/19) each. There is a great disparity between the established ubiquity in environmental sources and the number of cases of FLA infections in the country. FLA-related research in the Philippines is still in its inceptive stage with several gaps to fill, which can be used to formulate policy briefs in the future regarding its isolation, identification, diagnosis, therapeutic management, and control of FLA infections in the country.
Topics: Amebiasis; Amoeba; Environmental Monitoring; Epidemiological Monitoring; Humans; Philippines; Public Health
PubMed: 35112656
DOI: 10.1080/20477724.2022.2035626 -
Pathogens and Global Health Mar 2022Pathogenic free-living amoebae affecting the central nervous system are known to cause granulomatous amoebic encephalitis (GAE) or primary amoebic meningoencephalitis...
Pathogenic free-living amoebae affecting the central nervous system are known to cause granulomatous amoebic encephalitis (GAE) or primary amoebic meningoencephalitis (PAM). Although hosts with impaired immunity are generally at a higher risk of severe disease, amoebae such as and can instigate disease in otherwise immunocompetent individuals, whereas species mostly infect immunocompromised people. also cause a sight-threatening eye infection, mostly in contact lens wearers. Although infections due to pathogenic amoebae are considered rare, recently, these deadly amoebae were detected in water supplies in the USA. This is of particular concern, especially with global warming further exacerbating the problem. Herein, we describe the epidemiology, presentation, diagnosis, and management of free-living amoeba infections.
Topics: Acanthamoeba; Amebiasis; Amoeba; Balamuthia mandrillaris; Humans; Naegleria fowleri
PubMed: 34602025
DOI: 10.1080/20477724.2021.1985892 -
Medicina (Kaunas, Lithuania) Aug 2019is one of the most important water-related pathogens. Inside the water supply systems and the biofilms, interact with other bacteria and free-living amoeba (FLA)....
is one of the most important water-related pathogens. Inside the water supply systems and the biofilms, interact with other bacteria and free-living amoeba (FLA). Several amoebas may serve as hosts for bacteria in aquatic systems. This study aimed to investigate the co-occurrence of spp. and FLA in drinking water supply systems. A total of 268 water samples were collected from apartment buildings, hotels, and public buildings. Detection of spp. was performed in accordance with ISO 11731:2017 standard. Three different polymerase chain reaction (PCR) protocols were used to identify FLA. Occurrence of varied from an average of 12.5% in cold water samples with the most frequent occurrence observed in hot water, in areas receiving untreated groundwater, where 54.0% of the samples were positive. The occurrence of FLA was significantly higher. On average, 77.2% of samples contained at least one genus of FLA and, depending on the type of sample, the occurrence of FLA could reach 95%. In the samples collected during the study, was always isolated along with FLA, no samples containing in the absence of FLA were observed. The data obtained in our study can help to focus on the extensive distribution, close interaction, and long-term persistence of and FLA. Lack of risk management plans and control procedures may promote further spread of in water supply systems. In addition, the high incidence of -related FLA suggests that traditional monitoring methods may not be sufficient for control.
Topics: Amoeba; Drinking Water; Environmental Monitoring; Legionella; Water Microbiology; Water Supply
PubMed: 31443316
DOI: 10.3390/medicina55080492 -
Protist Feb 2022The Vampyrellida (Endomyxa, Rhizaria) is a group of free-living, predatory amoebae, which is most closely related to the Phytomyxea (plasmodiophorids and phagomyxids).... (Review)
Review
The Vampyrellida (Endomyxa, Rhizaria) is a group of free-living, predatory amoebae, which is most closely related to the Phytomyxea (plasmodiophorids and phagomyxids). It encompasses about 50 credibly described species that have a characteristic life history with the regular alternation of trophic amoebae and immobile digestive cysts. All known vampyrellid amoebae are naked and filose, but the different species display a broad morphological variety. Vampyrellids also vary greatly in their feeding habits, and range from generalist predators to specialized 'protoplast feeders' that exclusively feed on the cell contents of eukaryotic prey. They can be found in freshwater, soil and marine habitats, and appear to be globally distributed. Yet, the phenotypic diversity and ecological roles of the Vampyrellida are still poorly explored. Currently, there are eight well-recognized subclades that comprise four families (Vampyrellidae, Leptophryidae, Placopodidae and Sericomyxidae) as well as some lineages without any phenotypic information. Research on vampyrellids is challenging due to their cryptic occurrence in nature, intricate feeding habits that complicate cultivation, and a convoluted taxonomic history. Here, we review available information about cell structure, diversity, ecology, taxonomy and phylogenetics, and provide an up-to-date introduction to the Vampyrellida that may facilitate future research.
Topics: Amoeba; Cercozoa; Ecosystem; Humans; Phylogeny; Rhizaria
PubMed: 35091168
DOI: 10.1016/j.protis.2021.125854 -
BMC Biology Mar 2022Mitochondria and peroxisomes are the two organelles that are most affected during adaptation to microoxic or anoxic environments. Mitochondria are known to transform...
BACKGROUND
Mitochondria and peroxisomes are the two organelles that are most affected during adaptation to microoxic or anoxic environments. Mitochondria are known to transform into anaerobic mitochondria, hydrogenosomes, mitosomes, and various transition stages in between, collectively called mitochondrion-related organelles (MROs), which vary in enzymatic capacity. Anaerobic peroxisomes were identified only recently, and their putatively most conserved function seems to be the metabolism of inositol. The group Archamoebae includes anaerobes bearing both anaerobic peroxisomes and MROs, specifically hydrogenosomes in free-living Mastigamoeba balamuthi and mitosomes in the human pathogen Entamoeba histolytica, while the organelles within the third lineage represented by Pelomyxa remain uncharacterized.
RESULTS
We generated high-quality genome and transcriptome drafts from Pelomyxa schiedti using single-cell omics. These data provided clear evidence for anaerobic derivates of mitochondria and peroxisomes in this species, and corresponding vesicles were tentatively identified in electron micrographs. In silico reconstructed MRO metabolism harbors respiratory complex II, electron-transferring flavoprotein, a partial TCA cycle running presumably in the reductive direction, pyruvate:ferredoxin oxidoreductase, [FeFe]-hydrogenases, a glycine cleavage system, a sulfate activation pathway, and an expanded set of NIF enzymes for iron-sulfur cluster assembly. When expressed in the heterologous system of yeast, some of these candidates localized into mitochondria, supporting their involvement in the MRO metabolism. The putative functions of P. schiedti peroxisomes could be pyridoxal 5'-phosphate biosynthesis, amino acid and carbohydrate metabolism, and hydrolase activities. Unexpectedly, out of 67 predicted peroxisomal enzymes, only four were also reported in M. balamuthi, namely peroxisomal processing peptidase, nudix hydrolase, inositol 2-dehydrogenase, and D-lactate dehydrogenase. Localizations in yeast corroborated peroxisomal functions of the latter two.
CONCLUSIONS
This study revealed the presence and partially annotated the function of anaerobic derivates of mitochondria and peroxisomes in P. schiedti using single-cell genomics, localizations in yeast heterologous systems, and transmission electron microscopy. The MRO metabolism resembles that of M. balamuthi and most likely reflects the state in the common ancestor of Archamoebae. The peroxisomal metabolism is strikingly richer in P. schiedti. The presence of myo-inositol 2-dehydrogenase in the predicted peroxisomal proteome corroborates the situation in other Archamoebae, but future experimental evidence is needed to verify additional functions of this organelle.
Topics: Amoeba; Anaerobiosis; Archamoebae; Genomics; Humans; Mitochondria; Peroxisomes; Saccharomyces cerevisiae
PubMed: 35227266
DOI: 10.1186/s12915-022-01247-w -
Frontiers in Cellular and Infection... 2018A small subset of bacteria in soil interact directly with eukaryotes. Which ones do so can reveal what is important to a eukaryote and how eukaryote defenses might be...
A small subset of bacteria in soil interact directly with eukaryotes. Which ones do so can reveal what is important to a eukaryote and how eukaryote defenses might be breached. Soil amoebae are simple eukaryotic organisms and as such could be particularly good for understanding how eukaryote microbiomes originate and are maintained. One such amoeba, , has both permanent and temporary associations with bacteria. Here we focus on culturable bacterial associates in order to interrogate their relationship with . To do this, we isolated over 250 fruiting body samples from soil and deer feces at Mountain Lake Biological Station. In one-third of the wild we tested, one to six bacterial species were found per fruiting body sorus (spore mass) for a total of 174 bacterial isolates. The remaining two-thirds of fruiting body samples did not contain culturable bacteria, as is thought to be the norm. A majority (71.4%) of the unique bacterial haplotypes are in Proteobacteria. The rest are in either Actinobacteria, Bacteriodetes, or Firmicutes. The highest bacterial diversity was found in fruiting bodies originating from deer feces (27 OTUs), greater than either of those originating in shallow (11 OTUs) or in deep soil (4 OTUs). Rarefaction curves and the Chao1 estimator for species richness indicated the diversity in any substrate was not fully sampled, but for soil it came close. A majority of the -associated bacteria were edible by and supported its growth (75.2% for feces and 81.8% for soil habitats). However, we found several bacteria genera were able to evade phagocytosis and persist in cells through one or more social cycles. This study focuses not on the entire microbiome, but on the culturable subset of bacteria that have important eukaryote interactions as prey, symbionts, or pathogens. These eukaryote and bacteria interactions may provide fertile ground for investigations of bacteria using amoebas to gain an initial foothold in eukaryotes and of the origins of symbiosis and simple microbiomes.
Topics: Amoeba; Animals; Bacteria; Biodiversity; Deer; Dictyostelium; Feces; Microbiota; Phagocytosis; Phylogeny; Soil; Soil Microbiology; Symbiosis; Virginia
PubMed: 30533398
DOI: 10.3389/fcimb.2018.00411 -
Frontiers in Cellular and Infection... 2022A variety of bacteria have evolved the ability to interact with environmental phagocytic predators such as amoebae, which may have facilitated their subsequent...
A variety of bacteria have evolved the ability to interact with environmental phagocytic predators such as amoebae, which may have facilitated their subsequent interactions with phagocytes in animal hosts. Our recent study found that the animal pathogen can evade predation by the common soil amoeba , survive within, and hijack its complex life cycle as a propagation and dissemination vector. However, it is uncertain whether the mechanisms allowing interactions with predatory amoebae are conserved among species, because divergence, evolution, and adaptation to different hosts and ecological niches was accompanied by acquisition and loss of many genes. Here we tested 9 diverse species in three assays representing distinct aspects of their interactions with . Several human and animal pathogens retained the abilities to survive within single-celled amoeba, to inhibit amoebic plaque expansion, and to translocate with amoebae to the fruiting body and disseminate along with the fruiting body. In contrast, these abilities were partly degraded for the bird pathogen , and for the human-restricted species and . Interestingly, a different lineage of only known to infect sheep retained the ability to interact with , demonstrating that these abilities were lost in multiple lineages independently, correlating with niche specialization and recent rapid genome decay apparently mediated by insertion sequences. has been isolated sporadically from diverse human and environmental sources, has acquired insertion sequences, undergone genome decay and has also lost the ability to interact with amoebae, suggesting some specialization to some unknown niche. A genome-wide association study (GWAS) identified a set of genes that are potentially associated with the ability to interact with . These results suggest that massive gene loss associated with specialization of some species to a closed life cycle in a particular host was repeatedly and independently accompanied by loss of the ability to interact with amoebae in an environmental niche.
Topics: Amoeba; Animals; Bordetella; Bordetella bronchiseptica; Dictyostelium; Genome-Wide Association Study; Sheep
PubMed: 35223538
DOI: 10.3389/fcimb.2022.798317