Bacteria are bigger and more complex than viruses, though they can still spread through the air. A bacterium is a single cell, and it can live and reproduce almost anywhere on its own: in soil, in water and in our bodies.

Size of Bacterial Cell The average diameter of spherical bacteria is 0.5-2.0 µm. For rod-shaped or filamentous bacteria, length is 1-10 µm and diameter is 0.25-1 .

Cell morphology

Most Gram-positive bacteria have a relatively thick (about 20 to 80 nm), continuous cell wall (often called the sacculus), which is composed largely of peptidoglycan (also known as mucopeptide or murein).

about 1000 nanometers

Protozoa are single celled organisms. They come in many different shapes and sizes ranging from an Amoeba which can change its shape to Paramecium with its fixed shape and complex structure. They live in a wide variety of moist habitats including fresh water, marine environments and the soil.

Protozoan infections are responsible for diseases that affect many different types of organisms, including plants, animals, and some marine life. Many of the most prevalent and deadly human diseases are caused by a protozoan infection, including African Sleeping Sickness, amoebic dysentery, and malaria.

Protozoa are microscopic, one-celled organisms that can be free-living or parasitic in nature. They are able to multiply in humans, which contributes to their survival and also permits serious infections to develop from just a single organism.

Protozoa. Protozoa play important roles in environmental food web dynamics. They graze on bacteria thus regulating bacterial populations, they part-take in wastewater treatment processes, they maintain fertility in soil by releasing nutrients when they digest bacteria.

Viruses cause familiar infectious diseases such as the common cold, flu and warts. They also cause severe illnesses such as HIV/AIDS, Ebola, and COVID-19. Viruses are like hijackers.

The microscopic ova and parasite examination (O&P) is the traditional method for stool parasite testing. Although the O&P is labor-intensive and requires a high level of skill for optimal interpretation, this test remains the cornerstone of diagnostic testing for the intestinal protozoa.

The signs of a parasite are often caused by the toxins that it releases into the human bloodstream. Here are the most common symptoms: Unexplained constipation, diarrhea, gas, bloating, nausea or other symptoms of Irritable Bowel Syndrome. You traveled internationally and got diarrhea on your trip.

Some parasites enter the body by way of contaminated food or water and some live on the skin and the hair. Examples of parasites include: stomach and gut worms (threadworm, hookworm) skin mites (scabies)