"A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells."
Types of microorganisms that cause infectious diseases, such as bacteria, viruses, fungi, protozoa, and helminths.
Microbial anatomy and physiology: This topic covers the structure and function of microorganisms, including their cellular components, metabolic pathways, and growth cycles.
Microbial genetics: This topic covers the transmission and expression of microbial genetic material, including DNA replication, transcription, translation, and mutation.
Microbial ecology: This topic covers the relationships among microorganisms and their environment, including the roles of microorganisms in nutrient cycling, bioremediation, and disease transmission.
Host-pathogen interactions: This topic covers the mechanisms by which microorganisms cause disease, including virulence factors, host susceptibility, and immune response.
Epidemiology: This topic covers the spread and control of infectious diseases within populations, including disease surveillance, outbreak investigation, and intervention strategies.
Antimicrobial agents: This topic covers the mechanisms and efficacy of antimicrobial agents, including antibiotics, antivirals, and antifungals.
Microbial pathogenesis: This topic covers the mechanisms by which microorganisms cause disease, including colonization, invasion, and dissemination.
Immunology: This topic covers the immune response to infectious agents, including innate and adaptive immunity, antigen recognition, and immune evasion.
Diagnostic methods: This topic covers the laboratory detection and identification of microorganisms, including culture-based, serologic, and molecular methods.
Public health measures: This topic covers the policies and practices aimed at preventing and controlling infectious diseases at the population level, including vaccination, sanitation, and quarantine measures.
Bacteria: Single-celled organisms that can survive independently, but can also cause infections that vary from mild to life-threatening. Examples include streptococcus, staphylococcus, tuberculosis, etc.
Viruses: Tiny infectious agents with genetic material, enclosed in a protein coat, that can replicate inside host cells, causing various infectious diseases from the common cold to HIV, influenza, and Ebola.
Fungi: Multicellular or unicellular microorganisms that thrive in warm, moist environments and can cause skin infections (e.g., ringworm), thrush, athlete's foot, etc.
Protozoa: Single-celled organisms that can infect human and animal hosts and cause diseases such as malaria, toxoplasmosis, and amoebic dysentery.
Parasites: Typically larger than other microbes, they can dwell inside or outside human hosts and cause various infections like trichomoniasis, leishmaniasis, Chagas disease, etc.
Prions: Abnormally folded proteins that can cause degenerative neurological diseases, like Creutzfeldt-Jakob disease.
Rickettsiae: Intracellular bacteria transmitted by ticks or fleas that can cause conditions like Rocky Mountain spotted fever.
Mycoplasma: Bacteria with no cell wall that are sometimes classified as fungi; they can cause pneumonia, urethritis, and other respiratory infections.
Chlamydia: Bacteria-like microorganisms that can cause sexually transmitted infections, like chlamydia and lymphogranuloma venereum.
"The scientific study of microorganisms began with their observation under the microscope in the 1670s by Anton van Leeuwenhoek."
"In the 1850s, Louis Pasteur found that microorganisms caused food spoilage, debunking the theory of spontaneous generation."
"In the 1880s, Robert Koch discovered that microorganisms caused the diseases tuberculosis, cholera, diphtheria, and anthrax."
"Because microorganisms include most unicellular organisms from all three domains of life they can be extremely diverse."
"Some are adapted to extremes such as very hot or very cold conditions, others to high pressure, and a few, such as Deinococcus radiodurans, to high radiation environments."
"Microorganisms also make up the microbiota found in and on all multicellular organisms."
"There is evidence that 3.45-billion-year-old Australian rocks once contained microorganisms, the earliest direct evidence of life on Earth."
"Microbes are important in human culture and health in many ways, serving to ferment foods and treat sewage, and to produce fuel, enzymes, and other bioactive compounds."
"Microbes are essential tools in biology as model organisms."
"Microbes have been put to use in biological warfare and bioterrorism."
"Microbes are a vital component of fertile soil."
"In the human body, microorganisms make up the human microbiota, including the essential gut flora."
"The pathogens responsible for many infectious diseases are microbes and, as such, are the target of hygiene measures."
"The possible existence of unseen microbial life was suspected from ancient times, such as in Jain scriptures from the sixth century BC India."
"The two of the three domains, Archaea and Bacteria, only contain microorganisms."
"There are also many multicellular organisms that are microscopic, namely micro-animals, some fungi, and some algae, but these are generally not considered microorganisms."
"Microorganisms can have very different habitats, and live everywhere from the poles to the equator, deserts, geysers, rocks, and the deep sea."
"Some are adapted to extremes such as very hot or very cold conditions, others to high pressure, and a few, such as Deinococcus radiodurans, to high radiation environments."
"Microorganisms serve to ferment foods and treat sewage."