Naegleria Fowleri
Domain: Eukaryota
Kingdom: Protista
Phylum: Percoloza
Class: Heterolobosea
Order: Schizopyrenida
Family: Vahlkampfiidae
Genus: Naegleria
Species: fowleri
Naegleria fowleri is a type of protist, specifically amoeba, that is also known by the common name “brain-eating amoeba”. N. fowleri conforms with the basic description of all protists: it is a eukaryotic organism that does not fit in with the descriptions of plants, animals or fungi. This amoeba is unicellular, as most protists are, and is a pathogenic organism that can cause brain infection. Like all protists, N. fowleri prefers a wet environment, specifically warm freshwater and damp soil, and also likes warm temperatures, ideally 42 degrees Celsius [28], [29]. One interesting thing about the N. fowleri is that in order to obtain food, they will use a food-cup to help them ingest bacteria and yeast, as well as cells when in inside the human body.
During its lifecycle, the brain-eating amoeba can change its form between three different recognizable shapes. The first shape is the trophozoite, which is the form that the N. fowleri takes during the infective stage of its life. While in this shape, this amoeba is between 10 and 20 mm long [29]. Also, the trophozoite shape of N. fowleri has a big chromosome (called a karyosome) and is surrounded by a halo. Another characteristic of this shape is that, in accordance with the majority of protists, trophozoites reproduce through binary fission, and they are able to move with the help of lobopodia, a type of pseudopodia which are a common mode of protistan motility. The next shape is the flagellate. N. fowleri will enter the flagellate stage when there is change of pH in its environment. The change between trophozoites and flagellates can be done by the amoeba in as little as a few minutes to a few hours [29]. In this form, the N. fowleri has two flagella and is longer. Finally, in adverse conditions such as not enough nutrients, too cold or too dry temperatures, N. fowleri can change into cysts. When in cyst form, the amoeba 8 to 15 mm long and round [29]. Nevertheless, when reintroduced into benign environments, the N. fowleri can quickly change back into the trophozoite form and and once more be infectious.
As mentioned earlier, Naegleria fowleri can cause an infection in a human’s brain, and it is the only species within the genus Naegleria that can infect people. While usually this amoeba will feed off of bacteria, it can enter a human’s brain through their nose while that person is in fresh water. Then, it will cause an infection to the brain called primary amebic meningoencephalitis (PAM), hence its common name, brain-eating amoeba, by killing and ingesting the neurons in the brain [28].
Paramecium caudatum
Domain: Eukaryota
Kingdom: Protista
Phylum: Ciliophora
Class: Ciliatea
Subclass: Rhabdophorina
Order: Hymenostomatida
Suborder: Peniculina
Family: Parameciidae
Genus: Paramecium
Species: Caudatum
Paramecium caudatum is a type of protist that, like the majority of protists, is eukaryotic and unicellular [30]. Another characteristic of P. caudatum that fits within the classification of Protists is its mode of nutrition. All protists are either photosynthesizers or obtain their food by ingesting bacteria and various other organic particles. P. caudatum fits into the latter group, procuring food through heterotrophic means. They will ingest bacteria, as well as some yeasts, algae, and small protozoa through phagocytosis [30]. One paramecium can actually ingest up to 5,000 bacteria in a single day. P. caudatum, like most protists, also have a limited form of motility. Specifically, they have cilia that cover their entire body that are able to push it along. Also, this paramecium does not have a nervous system, a characteristic that holds true in the entire kingdom of Protista. Finally, P. caudatum can reproduce both sexually, through conjugation, and asexually, through binary fission [30].
P. caudatum can be between 120 and 330 micrometers in length. It is elongate, with cilia, longer on its rear end, that aid it in motility. This paramecium also has a long oral groove leading to an oral cavity that is also lined with cilia [31]. The P. caudatum has two nuclei, a macronucleus and a micronucleus [30,31]. It also has two star- shaped contractile vacuoles that contract to let water out of the cell. They are commonly found in salty, brackish and freshwater environments [31].
Paramecium caudatum reproduce both sexually and asexually. Binary fission, (which is asexual,) is their main mode of reproduction, and a paramecium will often reproduce this way two to three times a day. During binary fission, the macronucleus of the P. caudatum will elongate, then eventually split into two [30]. The P. caudatum can also reproduce sexually through conjugation, although this usually only occurs under stressful conditions for the paramecium. During this process, two paramecium will temporarily join together by a bridge of cytoplasm called a conjugation bridge. The micronucleus of each organism will then go through meiosis to form 4 haploid micronuclei, three of which disintegrate. The fourth one will go through mitosis, then fuse with the micronuclei from the other cell. The macronucleus will also disintegrate and be replaced during conjugation [30].
P. caudatum eat by feeding on bacteria as well and some small eukaryotic cells. They can release a small structure called a trichocyte, which helps them detect food within their surroundings. It will also obtain other nutrients in the water around it through osmosis [30].
