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Viruses Jan 2022Almost two decades after the isolation of the first amoebal giant viruses, indubitably the discovery of these entities has deeply affected the current scientific... (Review)
Review
Almost two decades after the isolation of the first amoebal giant viruses, indubitably the discovery of these entities has deeply affected the current scientific knowledge on the virosphere. Much has been uncovered since then: viruses can now acknowledge complex genomes and huge particle sizes, integrating remarkable evolutionary relationships that date as early as the emergence of life on the planet. This year, a decade has passed since the first studies on giant viruses in the Brazilian territory, and since then biomes of rare beauty and biodiversity (Amazon, Atlantic forest, Pantanal wetlands, Cerrado savannas) have been explored in the search for giant viruses. From those unique biomes, novel viral entities were found, revealing never before seen genomes and virion structures. To celebrate this, here we bring together the context, inspirations, and the major contributions of independent Brazilian research groups to summarize the accumulated knowledge about the diversity and the exceptionality of some of the giant viruses found in Brazil.
Topics: Amoeba; Biodiversity; Brazil; Ecosystem; Genome, Viral; Giant Viruses; History, 21st Century; Phylogeny; Virology
PubMed: 35215784
DOI: 10.3390/v14020191 -
The International Journal of... 2019Social amoebae and humans use common strategies to orchestrate their interactions with the bacteria in their respective environments and within their bodies. These... (Comparative Study)
Comparative Study Review
Social amoebae and humans use common strategies to orchestrate their interactions with the bacteria in their respective environments and within their bodies. These strategies include the elimination of bacteria by phagocytosis, the establishment of mutualistic interactions, the elaboration of physical barriers, and the deployment of innate immune cells. Many of the molecular mechanisms that humans and social amoebae employ differ, but there are striking similarities that may inform studies in each organism. In this topical review we highlight the similarities and consider what we might learn by comparing these highly divergent species. We focus on recent work in Dictyostelium discoideum with hopes of stimulating work in this area and with the expectation that new mechanistic details uncovered in social amoebae-bacteria interactions will inform microbiome management in humans.
Topics: Animals; Bacteria; Dictyostelium; Extracellular Traps; Humans; Intestines; Lectins; Mice; Microbiota; Phagocytosis; Soil; Symbiosis
PubMed: 31840783
DOI: 10.1387/ijdb.190240ak -
PloS One 2022Free-living amoebae (FLA) are gaining attention due to the increasing number of related grave central nervous system (CNS) and sight-threatening eye infections and their...
Isolation and morphological and molecular characterization of waterborne free-living amoebae: Evidence of potentially pathogenic Acanthamoeba and Vahlkampfiidae in Assiut, Upper Egypt.
Free-living amoebae (FLA) are gaining attention due to the increasing number of related grave central nervous system (CNS) and sight-threatening eye infections and their role as Trojan horses for many bacteria and viruses. This study was conducted in Assiut City, Egypt to detect the presence of FLA in different water sources using morphological and molecular approaches and determine their potential pathogenicity. A total of 188 water samples (100 tap, 80 tank, and 8 swimming pool samples) were collected, cultivated on non-nutrient agar seeded with Escherichia coli, and inspected for FLA. Thermo- and osmo-tolerance assays were performed to determine their pathogenicity. Polymerase chain reaction and sequence analysis were performed to confirm the identification and analyze the genotype. Overall, 52 samples (27.7%) were positive for FLA. Of these, 20.7% were identified as Acanthamoeba, 1.6% as Vahlkampfiidae, and 5.3% as mixed Acanthamoeba and Vahlkampfiidae. Seven species of Acanthamoeba were recognized, of which A. triangularis, A. polyphaga, A. lenticulata, and A. culbertsoni are thermo- and osmo-tolerant, and A. astronyxis, A. comandoni, and A. echinulata are non-thermo- and non-osmo-tolerant. The phylogeny analysis revealed T4 and T7 genotypes. Among Vahlkampfiids, 61.5% were identified as thermo- and osmo-tolerant Vahlkampfia, and 30.8% were identified as non-pathogenic Naegleria. One isolate (7.7%) was identified as potentially pathogenic Allovahlkampfia, as confirmed by sequencing. This is the first report documenting the occurrence and phylogeny of waterborne FLA (Acanthamoeba/Vahlkampfiidae) in Assiut, Egypt. The presence of potentially pathogenic FLA highlights the possible health hazards and the need for preventive measures.
Topics: Acanthamoeba; Amoeba; Egypt; Naegleria; Water
PubMed: 35802617
DOI: 10.1371/journal.pone.0267591 -
Pathogens (Basel, Switzerland) Oct 2022Free-living amoebae (FLA) are protozoa widely distributed in the environment, found in a great diversity of terrestrial biomes. Some genera of FLA are linked to human... (Review)
Review
Free-living amoebae (FLA) are protozoa widely distributed in the environment, found in a great diversity of terrestrial biomes. Some genera of FLA are linked to human infections. The genus is currently classified into 23 genotypes (T1-T23), and of these some (T1, T2, T4, T5, T10, T12, and T18) are known to be capable of causing granulomatous amoebic encephalitis (GAE) mainly in immunocompromised patients while other genotypes (T2, T3, T4, T5, T6, T10, T11, T12, and T15) cause keratitis mainly in otherwise healthy patients. Meanwhile, is the causative agent of an acute infection called primary amoebic meningoencephalitis (PAM), while , like some genotypes, causes GAE, differing from the latter in the description of numerous cases in patients immunocompetent. Finally, other FLA related to the pathologies mentioned above have been reported; sp. is responsible for one case of amoebic encephalitis; has been found in cases of ocular damage, and its extraordinary capacity as endocytobiont for microorganisms of public health importance such as , and , among others. This review addressed issues related to epidemiology, updating their geographic distribution and cases reported in recent years for pathogenic FLA.
PubMed: 36297255
DOI: 10.3390/pathogens11101199 -
Water Research Jun 2017Opportunistic premise (i.e., building) plumbing pathogens (OPPPs, e.g., Legionella pneumophila, Mycobacterium avium complex, Pseudomonas aeruginosa, Acanthamoeba, and... (Review)
Review
Opportunistic premise (i.e., building) plumbing pathogens (OPPPs, e.g., Legionella pneumophila, Mycobacterium avium complex, Pseudomonas aeruginosa, Acanthamoeba, and Naegleria fowleri) are a significant and growing source of disease. Because OPPPs establish and grow as part of the native drinking water microbiota, they do not correspond to fecal indicators, presenting a major challenge to standard drinking water monitoring practices. Further, different OPPPs present distinct requirements for sampling, preservation, and analysis, creating an impediment to their parallel detection. The aim of this critical review is to evaluate the state of the science of monitoring OPPPs and identify a path forward for their parallel detection and quantification in a manner commensurate with the need for reliable data that is informative to risk assessment and mitigation. Water and biofilm sampling procedures, as well as factors influencing sample representativeness and detection sensitivity, are critically evaluated with respect to the five representative bacterial and amoebal OPPPs noted above. Available culturing and molecular approaches are discussed in terms of their advantages, limitations, and applicability. Knowledge gaps and research needs towards standardized approaches are identified.
Topics: Amoeba; Drinking Water; Humans; Legionella pneumophila; Pseudomonas aeruginosa; Sanitary Engineering; Water Microbiology; Water Supply
PubMed: 28390237
DOI: 10.1016/j.watres.2017.03.046 -
Frontiers in Cell and Developmental... 2021The haploid social amoeba is a powerful model organism to study vesicle trafficking, motility and migration, cell division, developmental processes, and host... (Review)
Review
The haploid social amoeba is a powerful model organism to study vesicle trafficking, motility and migration, cell division, developmental processes, and host cell-pathogen interactions. Dynamin superfamily proteins (DSPs) are large GTPases, which promote membrane fission and fusion, as well as membrane-independent cellular processes. Accordingly, DSPs play crucial roles for vesicle biogenesis and transport, organelle homeostasis, cytokinesis and cell-autonomous immunity. Major progress has been made over the last years in elucidating the function and structure of mammalian DSPs. produces at least eight DSPs, which are involved in membrane dynamics and other processes. The function and structure of these large GTPases has not been fully explored, despite the elaborate genetic and cell biological tools available for . In this review, we focus on the current knowledge about mammalian and DSPs, and we advocate the use of the genetically tractable amoeba to further study the role of DSPs in cell and infection biology. Particular emphasis is put on the virulence mechanisms of the facultative intracellular bacterium .
PubMed: 34746129
DOI: 10.3389/fcell.2021.731964 -
Nature Protocols Jan 2024Giant viruses (GVs) provide an unprecedented source of genetic innovation in the viral world and are thus, besides their importance in basic and environmental virology,... (Review)
Review
Giant viruses (GVs) provide an unprecedented source of genetic innovation in the viral world and are thus, besides their importance in basic and environmental virology, in the spotlight for bioengineering advances. Their host, Acanthamoeba castellanii, is an accidental human pathogen that acts as a natural host and environmental reservoir of other human pathogens. Tools for genetic manipulation of viruses and host were lacking. Here, we provide a detailed method for genetic manipulation of A. castellanii and the GVs it plays host to by using CRISPR-Cas9 or homologous recombination. We detail the steps of vector preparation (4 d), transfection of amoeba cells (1 h), infection (1 h), selection (5 d for viruses, 2 weeks for amoebas) and cloning of recombinant viruses (4 d) or amoebas (2 weeks). This procedure takes ~3 weeks or 1 month for the generation of recombinant viruses or amoebas, respectively. This methodology allows the generation of stable gene modifications, which was not possible by using RNA silencing, the only previously available reverse genetic tool. We also include detailed sample-preparation steps for protein localization by immunofluorescence (4 h), western blotting (4 h), quantification of viral particles by optical density (15 min), calculation of viral lethal dose 50 (7 d) and quantification of DNA replication by quantitative PCR (4 h) to allow efficient broad phenotyping of recombinant organisms. This methodology allows the function of thousands of ORFan genes present in GVs, as well as the complex pathogen-host, pathogen-pathogen or pathogen-symbiont interactions in A. castellanii, to be studied in vivo.
Topics: Humans; Acanthamoeba castellanii; Giant Viruses; Viruses
PubMed: 37964008
DOI: 10.1038/s41596-023-00910-y -
Toxins Jul 2021Numerous microorganisms, pathogenic for mammals, come from the environment where they encounter predators such as free-living amoebae (FLA). The selective pressure due... (Review)
Review
Numerous microorganisms, pathogenic for mammals, come from the environment where they encounter predators such as free-living amoebae (FLA). The selective pressure due to this interaction could have generated virulence traits that are deleterious for amoebae and represents a weapon against mammals. Toxins are one of these powerful tools that are essential for bacteria or fungi to survive. Which amoebae are used as a model to study the effects of toxins? What amoeba functions have been reported to be disrupted by toxins and bacterial secreted factors? Do bacteria and fungi effectors affect eukaryotic cells similarly? Here, we review some studies allowing to answer these questions, highlighting the necessity to extend investigations of microbial pathogenicity, from mammals to the environmental reservoir that are amoebae.
Topics: Amoeba; Bacteria; Bacterial Toxins; Fungi; Mycotoxins; Phagocytosis
PubMed: 34437397
DOI: 10.3390/toxins13080526 -
Trends in Cell Biology Mar 2022Cell migration is essential for many biological processes, while abnormal cell migration is characteristic of cancer cells. Epithelial cells become motile by undergoing... (Review)
Review
Cell migration is essential for many biological processes, while abnormal cell migration is characteristic of cancer cells. Epithelial cells become motile by undergoing epithelial-to-mesenchymal transition (EMT), and mesenchymal cells increase migration speed by adopting amoeboid features. This review highlights how amoeboid behaviour is not merely a migration mode but rather a cellular state - within the EMT spectra - by which cancer cells survive, invade and colonise challenging microenvironments. Molecular biomarkers and physicochemical triggers associated with amoeboid behaviour are discussed, including an amoeboid associated tumour microenvironment. We reflect on how amoeboid characteristics support metastasis and how their liabilities could turn into therapeutic opportunities.
Topics: Amoeba; Cell Line, Tumor; Cell Movement; Epithelial-Mesenchymal Transition; Humans; Tumor Microenvironment
PubMed: 34836782
DOI: 10.1016/j.tcb.2021.10.004 -
Genes Mar 2021Multicellularity evolved repeatedly in the history of life, but how it unfolded varies greatly between different lineages. Dictyostelid social amoebas offer a good... (Comparative Study)
Comparative Study Review
Multicellularity evolved repeatedly in the history of life, but how it unfolded varies greatly between different lineages. Dictyostelid social amoebas offer a good system to study the evolution of multicellular complexity, with a well-resolved phylogeny and molecular genetic tools being available. We compare the life cycles of the Dictyostelids with closely related amoebozoans to show that complex life cycles were already present in the unicellular common ancestor of Dictyostelids. We propose frost resistance as an early driver of multicellular evolution in Dictyostelids and show that the cell signalling pathways for differentiating spore and stalk cells evolved from that for encystation. The stalk cell differentiation program was further modified, possibly through gene duplication, to evolve a new cell type, cup cells, in Group 4 Dictyostelids. Studies in various multicellular organisms, including Dictyostelids, volvocine algae, and metazoans, suggest as a common principle in the evolution of multicellular complexity that unicellular regulatory programs for adapting to environmental change serve as "proto-cell types" for subsequent evolution of multicellular organisms. Later, new cell types could further evolve by duplicating and diversifying the "proto-cell type" gene regulatory networks.
Topics: Amoeba; Biological Evolution; Cold Temperature; Dictyostelium; Evolution, Molecular; Life Cycle Stages; Phylogeny; Signal Transduction; Stress, Physiological
PubMed: 33801615
DOI: 10.3390/genes12040487