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What is a germ?

A germ is a microorganism that may cause disease. There are four major categories of germs: bacteria, fungi, protozoa, and viruses.

What are the four types of germs?

Germs are microorganisms that may cause disease. There are four major categories of germs: bacteria, fungi, protozoa, and viruses. Germs cannot be seen by the naked eye but they are everywhere around us; in the air, soil, ground, on our food and water, and on animals and humans. Different kinds of germs are unique, in that they all prefer to live in different environments and have their own ways of spreading and growing.

What are the differences between bacteria, fungi, protozoa, and viruses?

  • Bacteria are single-celled organisms that receive their nutrients from the environment around them. Bacteria can be beneficial (like for our gut microbiome) but can also be harmful and lead to issues like infections or cavities. 
  • Fungi are plant-like organisms that are multi celled. They get their nutrition from plants, food, and animals. They like damp and warm environments. Athlete’s foot and yeast infections are two common associations with fungi.
  • Protozoa are also one-celled organisms like bacteria. However they are larger than bacteria and have more complex cell structures. Protozoa also like moist environments.
  • Viruses are smaller than bacteria and solely contain genetic material (either DNA or RNA) within a protein coating. Viruses must use another cell’s structures to reproduce, and they cannot live very long outside of another living cell.

Does alcohol kill germs?

Alcohol can kill germs as long as it is in a high enough concentration. Hand sanitizers will need to have at least 60-95% alcohol and disinfecting alcohol cleaners need to have at least 70% alcohol in order to make them effective at killing germs according to the Centers for Disease Control and Prevention. Additionally, the alcohol should be applied for at least 25-30 seconds. It works by breaking down the cell walls of the microorganism. Alcohol may not be able to kill bacterial spores.

Does vinegar kill germs?

Vinegar can be a disinfectant to some degree. It has acetic acid which may help break down chemical structure of some dirt particles, oil, films, and bacteria. However it is not as effective at killing germs to other commercial disinfectants or bleach. Vinegar is only effective on certain types of germs but not all. The EPA recommends other methods for disinfecting.

Does hydrogen peroxide kill germs?

Hydrogen peroxide may be used to kill some types of organisms such as bacteria, mold spores, viruses, fungi, and yeast, but it must be used in the correct concentration and left on for a certain amount of time in order to be effective. Mosy hydrogen peroxide is sold in the stores at 3% concentration and works best if it is left on a surface for at least 10 minutes. If using hydrogen peroxide, use caution as it may stain clothing and surfaces. It can also be harmful if it touches the skin directly, which is why hydrogen peroxide is not used in hand sanitizers.

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Photo of Kristin Ricklefs-Johnson

Medically reviewed by:

Kristin Ricklefs-Johnson, Ph.D., RD

Kristin is an RDN who also earned her Ph.D. in Nutrition from Arizona State University with an emphasis on insulin resistance, lipid metabolism disorders, and obesity. She completed her post-doctoral fellowship at Mayo Clinic where she focused on nutrition-related proteomic and metabolic research. Her interests include understanding the exact mechanism of action of various genetic variations underlying individual predispositions to nutrition-related health outcomes. Her goal is to help all individuals prevent chronic diseases and achieve long, healthy lives through eating well.

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