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The germ theory of disease is the currently accepted scientific theory for many diseases. It states that microorganisms known as pathogens or "germs" can cause disease. These small organisms, which are too small to be seen without magnification, invade humans, other animals, and other living hosts. Their growth and reproduction within their ...
The combined domains of archaea and bacteria make up the most diverse and abundant group of organisms on Earth and inhabit practically all environments where the temperature is below +140 °C (284 °F). They are found in water, soil, air, as the microbiome of an organism, hot springs and even deep beneath the Earth's crust in rocks. [48]
Nearly all animal life is dependent on bacteria for survival as only bacteria and some archaea possess the genes and enzymes necessary to synthesise vitamin B 12, also known as cobalamin, and provide it through the food chain. Vitamin B 12 is a water-soluble vitamin that is involved in the metabolism of every cell of the
Infectious disease. Waterborne diseases are conditions (meaning adverse effects on human health, such as death, disability, illness or disorders) [ 1 ]: 47 caused by pathogenic micro-organisms that are transmitted by water. These diseases can be spread while bathing, washing, drinking water, or by eating food exposed to contaminated water. [ 2 ]
The term pathogen came into use in the 1880s. [ 2 ][ 3 ] Typically, the term pathogen is used to describe an infectious microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus. [ 4 ][ 5 ][ 6 ] Small animals, such as helminths and insects, can also cause or transmit disease. However, these animals are usually ...
Salmonella species can be found in the digestive tracts of humans and animals, especially reptiles. Salmonella on the skin of reptiles or amphibians can be passed to people who handle the animals. [39] Food and water can also be contaminated with the bacteria if they come in contact with the feces of infected people or animals. [40]
Three-domain system. The three-domain system is a taxonomic classification system that groups all cellular life into three domains, namely Archaea, Bacteria and Eukarya, introduced by Carl Woese, Otto Kandler and Mark Wheelis in 1990. [ 1 ] The key difference from earlier classifications such as the two-empire system and the five-kingdom ...
Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food.This includes the study of microorganisms causing food spoilage; pathogens that may cause disease (especially if food is improperly cooked or stored); microbes used to produce fermented foods such as cheese, yogurt, bread, beer, and wine; and microbes with other useful roles, such as producing ...