Archaea: refer to single-celled microorganisms, which contain no nucleus.

Amoeba: is a type of cell or organism which has the ability to change its shape.



Bifidobacteria: are a major group of bacteria which are found in many places in nature, such as the gut, mouth and on animals.

Bacteria: are single celled microorganisms that live in diverse environments. They can live in soil, the ocean and the human gut, just to name a few places. Some bacteria are extremophiles, which means they can survive in extreme conditions that are detrimental to most life forms, such as in glaciers, hydrothermal vents or alkaline lakes.

Bacteriophage: may also be called phage. They are a type of virus which attack bacteria and Archaea.



Carnivore: refers to an organism that gets its nutrients from eating only animal tissue. Examples include lions, tigers and other cat animals.

Caecum: is a pouch which is connected to the large intestine.

Ciliates: are a group of microorganisms which have hair-like particles called cilia on the outside of their cells.

Colon: the main part of the large intestine, which absorbs water and electrolytes from food which has remained undigested. It is home to the majority of the microbes in the human microbiome.



DNA: Stands for deoxyribonucleic acid. It contains the genetic instructions used to make all the cells in an organism.



Ecological Niche: is the role and position that an animal species has in its environment. The niche of a deer is to live in a forest habitat.

Eukaryote: is an organism whose cells are enclosed in membranes and also contain a nucleus (the brain of the cell which contains the DNA).



Fermentation: is the process by which a substance is broken down by bacteria, yeasts or other microorganisms.

Fungus: refer to microorganisms which include yeasts and moulds, including the more familiar mushrooms.



Herbivore: refers to an organisms which only eats plants. Examples include deer and rabbits.


Kefir: is a milk product which has been fermented by microorganisms.



Lactobacillus (plural = lactobacilli) is a rod shaped bacterium. Lactobacilli are involved in the fermentation of many food products we eat, such as cheese, meats and yogurt.



Microbe: is a small microorganism, such as bacteria, which have the ability to cause disease.

Microorganism: is a microscopic organism, invisible to the naked eye.

Microbiology: is the study of microscopic organisms, such as bacteria, viruses and fungi.

Microbiome: refers to all microorganisms living in a particular environment. The gut microbiome refers to the microbiome of the human gut.

Microbiota: is a community of microorganisms. A microbiota includes bacteria, archaea, fungi and viruses. The human microbiota refers to all of the microorganisms found in/on the human body.

MRSA: stands for Methicillin Resistant Staphylococcus Aureus. It is a type of bacteria which is resistant to most antibiotics and other forms of medicine. It is often referred to as a “superbug”.

Microbial diversity: refers to the broad variety of microorganisms present in a microbiota.


Photosynthesis: is a process used by plants to get energy. They convert light energy from the sun, into chemical energy which can be used by the cells in the plant.

Prokaryote: is an organism whose cells lack membranes and does not contain a nucleus.


Rumen: is another word for the first stomach of animals such as cows, sheep and goats. Interestingly, cows have four stomachs!


Virus: is a small infectious microorganism which lives by infecting the living cells of its host. Viruses can infect animals, plants and other microorganisms such as bacteria.


Yeast: are a type of fungus, which are used for a range of functions, including: baking, beer making, wine making and industrial processes.


If there are any other terms about microbiomes that you have seen or heard and do not understand, please contact us and we would be happy to explain. 

Likewise, if there are any terms you think we have left out, please contact us.


You can email us at info@worldmicrobiomeday.com and apc@ucc.ie