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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 -
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 -
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 -
Small (Weinheim An Der Bergstrasse,... Jun 2023Nature provides a successful evolutionary direction for single-celled organisms to solve complex problems and complete survival tasks - pseudopodium. Amoeba, a...
Nature provides a successful evolutionary direction for single-celled organisms to solve complex problems and complete survival tasks - pseudopodium. Amoeba, a unicellular protozoan, can produce temporary pseudopods in any direction by controlling the directional flow of protoplasm to perform important life activities such as environmental sensing, motility, predation, and excretion. However, creating robotic systems with pseudopodia to emulate environmental adaptability and tasking capabilities of natural amoeba or amoeboid cells remains challenging. Here, this work presents a strategy that uses alternating magnetic fields to reconfigure magnetic droplet into Amoeba-like microrobot, and the mechanisms of pseudopodia generation and locomotion are analyzed. By simply adjusting the field direction, microrobots switch in monopodia, bipodia, and locomotion modes, performing all pseudopod operations such as active contraction, extension, bending, and amoeboid movement. The pseudopodia endow droplet robots with excellent maneuverability to adapt to environmental variations, including spanning 3D terrains and swimming in bulk liquids. Inspired by the "Venom," the phagocytosis and parasitic behaviors have also been investigated. Parasitic droplets inherit all the capabilities of amoeboid robot, expanding their applicable scenarios such as reagent analysis, microchemical reactions, calculi removal, and drug-mediated thrombolysis. This microrobot may provide fundamental understanding of single-celled livings, and potential applications in biotechnology and biomedicine.
Topics: Amoeba; Locomotion; Physical Phenomena; Pseudopodia; Magnetic Fields
PubMed: 36869412
DOI: 10.1002/smll.202207360 -
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 -
Laboratory Medicine Sep 2023Primary amebic meningoencephalitis (PAM) is a fulminant fatal human disease caused by the free-living amoeba Naegleria fowleri. Infection occurs after inhalation of... (Review)
Review
Primary amebic meningoencephalitis (PAM) is a fulminant fatal human disease caused by the free-living amoeba Naegleria fowleri. Infection occurs after inhalation of water containing the amoeba, typically after swimming in bodies of warm freshwater. N. fowleri migrates to the brain where it incites meningoencephalitis and cerebral edema leading to death of the patient 7 to 10 days postinfection. Although the disease is rare, it is almost always fatal and believed to be underreported. The incidence of PAM in countries other than the United States is unclear and possibly on track to being an emerging disease. Poor prognosis is caused by rapid progression, suboptimal treatment, and underdiagnosis. As diagnosis is often performed postmortem and testing is only performed by a few laboratories, more accessible testing is necessary. This article reviews the current methods used in the screening and confirmation of PAM and makes recommendations for improved diagnostic practices and awareness.
Topics: Humans; United States; Central Nervous System Protozoal Infections; Brain; Meningoencephalitis; Naegleria fowleri; Clinical Laboratory Techniques; Amebiasis
PubMed: 36638160
DOI: 10.1093/labmed/lmac158