Amoeba: A genus of ameboid protozoa. Characteristics include a vesicular nucleus and the formation of several lodopodia, one of which is dominant at a given time. Reproduction occurs asexually by binary fission.Amebiasis: Infection with any of various amebae. It is an asymptomatic carrier state in most individuals, but diseases ranging from chronic, mild diarrhea to fulminant dysentery may occur.Acanthamoeba: A genus of free-living soil amoebae that produces no flagellate stage. Its organisms are pathogens for several infections in humans and have been found in the eye, bone, brain, and respiratory tract.Naegleria: A free-living soil amoeba pathogenic to humans and animals. It occurs also in water and sewage. The most commonly found species in man is NAEGLERIA FOWLERI which is the pathogen for primary amebic meningoencephalitis in primates.Acanthamoeba castellanii: A species of free-living soil amoebae in the family Acanthamoebidae. It can cause ENCEPHALITIS and KERATITIS in humans.Dictyostelium: A genus of protozoa, formerly also considered a fungus. Its natural habitat is decaying forest leaves, where it feeds on bacteria. D. discoideum is the best-known species and is widely used in biomedical research.Naegleria fowleri: A species of parasitic protozoa having both an ameboid and flagellate stage in its life cycle. Infection with this pathogen produces PRIMARY AMEBIC MENINGOENCEPHALITIS.Amoebida: An order of ameboid protozoa that is commonly uninucleate and possess mitochondria. Most organisms are nonpathogenic.Hartmannella: A genus of free-living amoebae found in fresh water. The cysts usually pass harmlessly through the intestinal tract of man and may thus be found in feces. Occasionally, these organisms cause respiratory tract infections or generalized fatal meningoencephalitis.Entamoeba histolytica: A species of parasitic protozoa causing ENTAMOEBIASIS and amebic dysentery (DYSENTERY, AMEBIC). Characteristics include a single nucleus containing a small central karyosome and peripheral chromatin that is finely and regularly beaded.Lobosea: A class of amoeboid EUKARYOTES that forms either filiform subpseudopodia or lobopodia. Characteristics include the absence of sorocarps, sporangia, or similar fruiting bodies. Lobosea were formerly members of the phylum Sarcomastigophora, subphylum Sarcodina, under the old five kingdom paradigm.Spores, Protozoan: A vegetative stage in the life cycle of sporozoan protozoa. It is characteristic of members of the phyla APICOMPLEXA and MICROSPORIDIA.Central Nervous System Protozoal Infections: Infections of the brain, spinal cord, or meninges by single celled organisms of the former subkingdom known as protozoa. The central nervous system may be the primary or secondary site of protozoal infection. These diseases may occur as OPPORTUNISTIC INFECTIONS or arise in immunocompetent hosts.Amebicides: Agents which are destructive to amebae, especially the parasitic species causing AMEBIASIS in man and animal.Legionella pneumophila: A species of gram-negative, aerobic bacteria that is the causative agent of LEGIONNAIRES' DISEASE. It has been isolated from numerous environmental sites as well as from human lung tissue, respiratory secretions, and blood.Chlamydiales: An order of obligately intracellular, gram-negative bacteria that have the chlamydia-like developmental cycle of replication. This is a two-stage cycle that includes a metabolically inactive infectious form, and a vegetative form that replicates by binary fission. Members of Chlamydiales are disseminated by aerosol or by contact. There are at least six recognized families: CHLAMYDIACEAE, Criblamydiaceae, Parachlamydiaceae, Rhabdochlamydia, Simkaniaceae, and Waddliaceae.Myxomycetes: A division of organisms that exist vegetatively as complex mobile plasmodia, reproduce by means of spores, and have complex life cycles. They are now classed as protozoa but formerly were considered fungi.Trophozoites: Cells or feeding stage in the life cycle of sporozoan protozoa. In the malarial parasite, the trophozoite develops from the MEROZOITE and then splits into the SCHIZONT. Trophozoites that are left over from cell division can go on to form gametocytes.Amoebozoa: A supergroup (some say phylum) of ameboid EUKARYOTES, comprising ARCHAMOEBAE; LOBOSEA; and MYCETOZOA.Dictyosteliida: An order of protozoa characterized by their ability to aggregate to form a multicellular pseudoplasmodium, which gives rise to a multispored fruiting body. A stalk tube is present.Entamoeba: A genus of ameboid protozoa characterized by the presence of beaded chromatin on the inner surface of the nuclear membrane. Its organisms are parasitic in invertebrates and vertebrates, including humans.Entamoebiasis: Infection with amoebae of the genus ENTAMOEBA. Infection with E. histolytica causes DYSENTERY, AMEBIC and LIVER ABSCESS, AMEBIC.Meningoencephalitis: An inflammatory process involving the brain (ENCEPHALITIS) and meninges (MENINGITIS), most often produced by pathogenic organisms which invade the central nervous system, and occasionally by toxins, autoimmune disorders, and other conditions.Protozoan Proteins: Proteins found in any species of protozoan.Acanthamoeba Keratitis: Infection of the cornea by an ameboid protozoan which may cause corneal ulceration leading to blindness.Mimiviridae: A family of nucleocytoplasmic, large, double-stranded DNA viruses with extremely complex genomes.Legionella: Gram-negative aerobic rods, isolated from surface water or thermally polluted lakes or streams. Member are pathogenic for man. Legionella pneumophila is the causative agent for LEGIONNAIRES' DISEASE.Liver Abscess, Amebic: Single or multiple areas of PUS due to infection by any ameboid protozoa (AMEBIASIS). A common form is caused by the ingestion of ENTAMOEBA HISTOLYTICA.Dimethyldithiocarbamate: A chemical that acts as a dopamine beta-hydroxylase inhibitor. Its salts are agricultural fungicides. It is inferior to diethyldithiocarbamate as a chelating agent.Genes, Protozoan: The functional hereditary units of protozoa.Eukaryota: One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.Dysentery, Amebic: DYSENTERY caused by intestinal amebic infection, chiefly with ENTAMOEBA HISTOLYTICA. This condition may be associated with amebic infection of the LIVER and other distant sites.Chemotaxis: The movement of cells or organisms toward or away from a substance in response to its concentration gradient.Physarum: A genus of protozoa, formerly also considered a fungus. Characteristics include the presence of violet to brown spores.DNA, Protozoan: Deoxyribonucleic acid that makes up the genetic material of protozoa.Physarum polycephalum: A protozoan, previously also considered a fungus. Characteristics include sporangia that are stalked and multilobed. It is widely used in biomedical research.Pinocytosis: The engulfing of liquids by cells by a process of invagination and closure of the cell membrane to form fluid-filled vacuoles.Microscopy, Electron: Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.Cytoplasmic Streaming: The movement of CYTOPLASM within a CELL. It serves as an internal transport system for moving essential substances throughout the cell, and in single-celled organisms, such as the AMOEBA, it is responsible for the movement (CELL MOVEMENT) of the entire cell.