Dive Into Microbiology With Interesting Protozoa Facts

Protozoa are single-celled organisms that feed primarily on bacteria and other protozoa, fungi, and other organisms.

The term ‘protozoa’ is derived from a Greek word that means ‘first animals’. These tiny organisms showcase animal-like behaviors.

They are known to be the descendants of one of the earliest forms of life. There are millions of different kinds of protozoa. And most of the varieties are so small that they cannot be seen by the naked eye. While some protozoa are free-living, some of them thrive in large groups or colonies.

Many varieties of these microorganisms are also called parasites. These parasites live and feed on plants and animals to survive, including humans. A protozoan parasite can live off a human body and make the host very sick, stealing all their essential nutrients.

About 50,000 protozoan species are known to exist and are found in humid or aquatic environments. Many of these species are symbionts, some are parasitic, while others are raiders of soil bacteria and algae.

Did you know that some protozoan species are also considered great for the environment as they make it more productive? They can improve water quality by eating all the bacteria and other particles. While water bacteria can be harmful to humans, soil bacteria are actually helpful as they support decomposition and convert energy into organic soil matter.

Structure Of Protozoa

Protozoa are unicellular eukaryotes. All the metabolic functions of protozoa are performed by some specific internal structures.

A protozoan mostly has only one membrane-bound nucleus in the cell. This nucleus is vesicular with scattered chromatin, giving it a diffused appearance. All the nuclei in an individual organism appear similar. But one of the vesicular nuclei houses a central body that is known as endosome or karyosome. The other nuclei of the nucleus contain DNA.

Furthermore, the ciliates have a micronucleus as well as a macronucleus that appear identical.

The plasma membrane encompasses the cytoplasm and projects the locomotor structure like the cilia, flagella, and pseudopodia. Membrane-bound cells organelles such as lysosomes, mitochondria, and other specialized structures are also present and function, similar to the organs of other animals.

Certain types of protozoa have cell mouth or cytosome for ingestion of food or bacteria. They have food vacuoles, where all the ingested food or bacteria comes. The central vacuole is present for osmoregulation, which is the removal of excess water.

Characteristics Of Protozoa

Protozoa are found in aquatic habitats, such as oceans or freshwater. Some of these organisms are free-living whereas the others can live as a parasite inside plants or animals. Some of the protozoan species are also found in extreme environmental conditions such as hot springs. They form resting cysts to overcome dry environments.

The shape and size of protozoan parasites can vary immensely. While some are microscopic (1µm), others are big enough to be seen by the naked eye. For instance, the shell of unicellular foraminifera may have a diameter as big as 7.9 in (20 cm).

Protozoa lack a rigid cell wall. For this reason, they are flexible and found in a myriad of different shapes.

Some specific types have a hard shell on the outer surface. Also, in certain varieties, especially ciliates, the cell is supported by a pellicle. This pellicle may be rigid or flexible, giving the organism its shape as well as helping in locomotion.

Protozoa have holozoic nutrition. This implies that these species require organic compounds that may be a solution or particulate. They ingest their food, which is mostly bacteria, via phagocytosis. Some protozoa even have a specialized structure for phagocytosis called a cytostome.

Their food is engulfed with a temporary mouth after which, the body of a protozoan performs the digestion and absorption of food vacuole. Finally, waste substance is ejected. Many protozoa also have a permanent mouth for ingesting food.

Almost all protozoa have flagella, pseudopodia, or cilia. These are structures that facilitate locomotion. One variety, sporozoa doesn’t have any locomotive structure. However, they have subpellicular microtubules that help with their slow movement.

Life Cycle Of Protozoa

Protozoa have two stages in their lifecycle. This includes proliferative stages (trophozoites) and dormant cysts.

When protozoa get exposed to very high temperatures or any other kind of extreme environmental conditions then it forms a dormant structure known as cysts. This transformation of a trophozoite into a cyst is called encystation.

During this stage, the protozoa can easily transmit from one host to another. When the environmental conditions go back to normal, they turn back into the trophozoite stage. At this stage, they actively feed.

Protozoa reproduce either by multiple fission or binary fission. Certain types also transfer their genetic material via conjugation.

Protozoa Examples

Protozoan species are broadly categorized into four groups, depending on their structure and locomotive arrangement.

Mastigophora Or Flagellates: Trichomonas, Trypanosoma, and Giardia Leishmania.

Amoeboids Or Sarcodina: Entamoeba and Amoeba.

Sporozoans Or Sporozoa: Myxidium, Plasmodium, Nosema, and Globidium.

Ciliates Or Ciliophora: Vorticella, Paramoecium, and Balantidium.

FAQs

What are protozoa?

Protozoa are single-celled organisms that are heterotrophic. They are either present as free-living microorganisms or protozoan parasites. According to scientists, there are over 50 thousand varieties of protozoa and parasites, and many of them cause diseases in humans and animals. Some of the most common disease-causing varieties include trypanosoma, plasmodium, and trichomonas.

What are the three types of protozoa?

Protozoa are mainly divided into four groups: the flagellates, the ameba, the sporozoa, and the ciliates.

Can protozoa be seen with the naked eye?

Most protozoa are minuscular and only a few grow to a size large enough to be seen by the naked eye.

Is amoeba a protozoan?

Yes, amoebas are considered unicellular protozoan organisms.

Where can we find protozoa?

Protozoa can be found in various moist habitats, such as marine environments, freshwater, and soil.