Prokaryotic cells (i.e., Bacteria and Archaea) are fundamentally different from the eukaryotic cells that constitute other forms of life. Prokaryotic cells are defined by a much simpler design than is found in eukaryotic cells.

Bacteria, also called germs, are microscopic organisms not visible with the naked eye. Bacteria are everywhere, both inside and outside of your body. Bacteria can live in a variety of environments, from hot water to ice. Some bacteria are good for you, while others can make you sick.

Bacteria are economically important as these microorganisms are used by humans for many purposes. The beneficial uses of bacteria include the production of traditional foods such as yogurt, cheese, and vinegar. Microbes are also important in agriculture for the compost and fertilizer production.

Like all other organisms, bacteria contain ribosomes for the production of proteins, but the structure of the bacterial ribosome is different from that of eukaryotes and Archaea. Some bacteria produce intracellular nutrient storage granules, such as glycogen, polyphosphate, sulfur or polyhydroxyalkanoates.

First seen as poisons, then as life-forms, then biological chemicals, viruses today are thought of as being in a gray area between living and nonliving: they cannot replicate on their own but can do so in truly living cells and can also affect the behavior of their hosts profoundly.

Because they can’t reproduce by themselves (without a host), viruses are not considered living. Nor do viruses have cells: they’re very small, much smaller than the cells of living things, and are basically just packages of nucleic acid and protein.

Two scientists contributed to the discovery of the first virus, Tobacco mosaic virus. Ivanoski reported in 1892 that extracts from infected leaves were still infectious after filtration through a Chamberland filter-candle. Bacteria are retained by such filters, a new world was discovered: filterable pathogens.

The English word “virus” is based on a Latin word for “poisonous secretion,” and early on it often kept to its original meaning of “venom,” either the literal or figurative kind.

Mimivirus is the largest and most complex virus known.

Viruses are much smaller. The largest of them are smaller than the smallest bacteria. Unlike bacteria, viruses can’t survive without a host. They can only reproduce by attaching themselves to cells.

Viruses are even smaller than bacteria and require living hosts — such as people, plants or animals — to multiply. Otherwise, they can’t survive. When a virus enters your body, it invades some of your cells and takes over the cell machinery, redirecting it to produce the virus.

Bacterial Infections Symptoms persist longer than the expected 10-14 days a virus tends to last.

The term “germs” refers to the microscopic bacteria, viruses, fungi, and protozoa that can cause disease. Washing hands well and often is the best way to prevent germs from leading to infections and sickness.

The four major types of germs are bacteria, viruses, fungi, and protozoa. They can invade plants, animals, and people, and sometimes they can make us sick. Bacteria (say: BAK-teer-ee-uh) are tiny, one-celled creatures that get nutrients from their environments in order to live.

Germs can get into the body through the mouth, nose, breaks in the skin, eyes and genitals (privates). Once disease-causing germs are inside the body they can stop it from working properly. They may breed very quickly and in a very short time a small number of germs can become millions.

The B lymphocytes (or B-cells) create antibodies and alert the T lymphocytes (or T-cells) to kill the pathogens. White blood cells are a part of the lymphatic system, a network of lymph vessels that collect excess fluids from tissues throughout the body and then return them to your bloodstream.

When germs invade the body, they get ready to stay for a while. These germs draw all their energy from the host. They may damage or destroy healthy cells. As they use up your nutrients and energy, they may make proteins known as toxins, which can help the germ in its mission to destroy.

Microbes inhabit just about every part of the human body, living on the skin, in the gut, and up the nose. Sometimes they cause sickness, but most of the time, microorganisms live in harmony with their human hosts, providing vital functions essential for human survival.

Your gut is home to most of the microbes in your body, but your skin, mouth, lungs, and genitalia also harbour diverse populations. And as research continues into body biomes, it should reveal answers about how these microorganisms are promoting health or even disease.

The area that was found to have the most bacteria at the time was the forearm, with a median of 44 species, followed by behind the ear with a median of 15 species.

While many people assume that the bathroom doorknob would be the dirtiest, the NSF found other spots that ranked higher with bacteria, including:

• bathroom light switches.
• refrigerator handles.
• stove knobs.
• microwave handles.