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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 -
Cells & Development Dec 2021Macropinocytosis is a form of endocytosis performed by ruffles and cups of the plasma membrane. These close to entrap droplets of medium into micron-sized vesicles,... (Review)
Review
Macropinocytosis is a form of endocytosis performed by ruffles and cups of the plasma membrane. These close to entrap droplets of medium into micron-sized vesicles, which are trafficked through the endocytic system, their contents digested and useful products absorbed. Macropinocytosis is constitutive in certain immune cells and stimulated in many other cells by growth factors. It occurs across the animal kingdom and in amoebae, implying a deep evolutionary history. Its scientific history goes back 100 years, but increasingly work is focused on its medical importance in the immune system, cancer cell feeding, and as a backdoor into cells for viruses and drugs. Macropinocytosis is driven by the actin cytoskeleton whose dynamics can be appreciated with lattice light sheet microscopy: this reveals a surprising variety of routes for forming macropinosomes. In Dictyostelium amoebae, macropinocytic cups are organized around domains of PIP3 and active Ras and Rac in the plasma membrane. These attract activators of the Arp2/3 complex to their periphery, creating rings of actin polymerization that shape the cups. The size of PIP3 domains is controlled by RasGAPs, such as NF1, and the lipid phosphatase, PTEN. It is likely that domain dynamics determine the shape, evolution and closing of macropinocytic structures.
Topics: Actin Cytoskeleton; Amoeba; Animals; Biology; Dictyostelium; Endocytosis; Pinocytosis
PubMed: 34175511
DOI: 10.1016/j.cdev.2021.203713 -
Current Biology : CB Sep 2021Macorano and Nowack provide an overview of Paulinella chromatophora, a filose amoeba that harbors an organelle called a chromatophore and only the second known case of a... (Review)
Review
Macorano and Nowack provide an overview of Paulinella chromatophora, a filose amoeba that harbors an organelle called a chromatophore and only the second known case of a eukaryote forming a primary endosymbiosis with a photosynthetic bacterium. Studying this relatively young relationship offers the chance to study the early stages of endosymbiosis.
Topics: Amoeba; Chromatophores; Photosynthesis; Rhizaria; Symbiosis
PubMed: 34520707
DOI: 10.1016/j.cub.2021.07.028 -
Genes Feb 2021Symbiosis is the living together of dissimilar organisms [...].
Symbiosis is the living together of dissimilar organisms [...].
Topics: Amoeba; Animals; Bacteria; Bacterial Physiological Phenomena; Biological Evolution; Evolution, Molecular; Fungi; Insecta; Plants; Symbiosis
PubMed: 33668704
DOI: 10.3390/genes12030327 -
The New Phytologist Sep 2021Endosymbiosis is a relationship between two organisms wherein one cell resides inside the other. This affiliation, when stable and beneficial for the 'host' cell, can... (Review)
Review
Endosymbiosis is a relationship between two organisms wherein one cell resides inside the other. This affiliation, when stable and beneficial for the 'host' cell, can result in massive genetic innovation with the foremost examples being the evolution of eukaryotic organelles, the mitochondria and plastids. Despite its critical evolutionary role, there is limited knowledge about how endosymbiosis is initially established and how host-endosymbiont biology is integrated. Here, we explore this issue, using as our model the rhizarian amoeba Paulinella, which represents an independent case of primary plastid origin that occurred c. 120 million yr ago. We propose the 'chassis and engine' model that provides a theoretical framework for understanding primary plastid endosymbiosis, potentially explaining why it is so rare.
Topics: Amoeba; Biological Evolution; Eukaryota; Phylogeny; Plastids; Symbiosis
PubMed: 34018613
DOI: 10.1111/nph.17478 -
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 -
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 -
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 -
JAAD International Mar 2022Balamuthia mandrillaris, a free-living amoeba, causes an uncommon infection that is characterized by cutaneous and neurological involvement, which carries a poor...
INTRODUCTION
Balamuthia mandrillaris, a free-living amoeba, causes an uncommon infection that is characterized by cutaneous and neurological involvement, which carries a poor prognosis.
METHODS
This is a retrospective observational study including patients with clinical suspicion of cutaneous balamuthiasis, their skin biopsies, and/or a positive direct immunofluorescence test. The data were collected from the Dermatology and Pathology service of the Hospital Cayetano Heredia and the Instituto Tropical Alexander von Humboldt, Lima, Peru, from January 1985 to June 2007. We identified 60 biopsies from 35 patients, from which clinical data were available in 30.
RESULTS
Twenty-two (73%) patients had centrofacial lesions, mostly located on the nose. The classical lesion was an asymptomatic, erythematous, or violaceous infiltrated plaque. Twenty-two (73%) patients had neurologic involvement. Fifty (83%) biopsies showed granulomatous dermatitis and 75% showed ill-defined tuberculoid granulomas without caseous necrosis. Multinucleated giant cells were observed in 52 (87%) biopsies. Trophozoite forms were identified in the biopsies of 25 (71%) patients. Direct immunofluorescence was positive in 25 (71%) patients.
CONCLUSION
is a pathogen that is capable of inducing a characteristic skin lesion with a reaction pattern of ill-defined tuberculoid granulomas and many giant cells.
PubMed: 35059659
DOI: 10.1016/j.jdin.2021.11.005