Entamoeba

Entamoeba is a group of tiny organisms that belong to the Amoebozoa. These tiny creatures can live inside animals, either helping them or causing problems. One important moment in history happened in 1875 when a scientist named Fedor Lösch found the first clear case of a sickness called amoebic dysentery in St. Petersburg, Russia. He saw these tiny creatures under a microscope and called them Amoeba coli.

Later, scientists gave these organisms a new name: Entamoeba. One type, Entamoeba histolytica, can make people very sick. A scientist named Fritz Schaudinn gave this name in 1903, but sadly, he later died from an infection while studying these organisms. For a while, scientists changed the name to Endamoeba, but they changed it back in the late 1950s, and the name Entamoeba has been used ever since.

Species

Several types of Entamoeba live in humans and animals. Entamoeba histolytica can cause sickness such as amoebiasis, which includes amoebic dysentery and amoebic liver abscesses. Other types like Entamoeba coli and Entamoeba dispar do not harm the host. Most Entamoeba species live in the intestines of their hosts, except for Entamoeba gingivalis which lives in the mouth, and E. moshkovskii, often found in river and lake sediments. Entamoeba invadens affects reptiles and can cause illness similar to E. histolytica. Many more species of Entamoeba may still be waiting to be discovered.

Structure

Entamoeba cells are tiny, with one nucleus and usually one lobose pseudopod, which looks like a clear bump at the front. These cells have a simple life cycle. The feeding form, called a trophozoite, is about 10 to 20 micrometers across and mainly eats bacteria. It splits into two smaller cells through a process called binary fission. Most kinds of Entamoeba create cysts, which help them move from one host to another. One exception is Entamoeba gingivalis, which does not form cysts. The number and size of nuclei in these cysts can help scientists tell different species apart.

Classification

Entamoeba is part of a group called the Archamoebae. These tiny living things do not need oxygen and have simpler versions of special parts inside their cells called mitochondria. Other similar organisms in this group include Endolimax and Iodamoeba, which also live inside animal intestines and look much like Entamoeba. There are also free-moving types such as those in the genus Mastigamoeba. Some other related organisms, like Endamoeba, might actually be the same as Entamoeba, but scientists are still figuring this out.

Culture

Scientists have studied how a type of tiny organism called Entamoeba invadens splits into two parts. They found that sometimes, one cell can’t split on its own, so it asks a nearby cell, called a “midwife,” to help. The midwife moves close and breaks the connection between the two new cells, letting all three move away.

Another similar organism, Dictyostelium, shows the same behavior. Researchers also use E. invadens to study how these organisms form protective shells because it’s easier to watch them grow without other living things around.

Differentiation and cell biology

Some tiny organisms called Uninucleated can change into special resting forms called cysts. This change is called encystation. The number of parts inside these cysts can differ between species, which helps scientists tell them apart. For example, one type forms cysts with eight parts, while others have four. Studying this process in detail is tricky for some species, so scientists use a related organism that causes similar sickness in reptiles. Recently, new tools were developed to help researchers study these changes better.

Meiosis

In tiny living things that can have babies, a special process called homologous recombination usually happens during meiosis. A special protein called Dmc1 helps this process in E. histolytica. This protein can pair up DNA and swap pieces of it, which is important for meiosis.

Studies in another type called E. invadens showed that when it changes from one form to another, homologous recombination gets better. Genes that help with meiosis also become more active during this change. This, along with what we see in E. histolytica, tells us that meiosis happens in Entamoeba.