Anthrax in the context of Eubacteria

A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in Jain literature authored in 6th-century BC India. 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.

Microorganisms are extremely diverse, representing most unicellular organisms in all three domains of life: two of the three domains, Archaea and Bacteria, only contain microorganisms. The third domain, Eukaryota, includes all multicellular organisms as well as many unicellular protists and protozoans that are microbes. Some protists are related to animals and some to green plants. Many multicellular organisms are also microscopic, namely micro-animals, some fungi, and some algae.

Bacteria are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit the air, soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in mutualistic, commensal and parasitic relationships with plants and animals. Most bacteria have not been characterised and there are many species that cannot be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.

Like all animals, humans carry vast numbers (approximately 10 to 10) of bacteria. Most are in the gut, though there are many on the skin. Most of the bacteria in and on the body are harmless or rendered so by the protective effects of the immune system, and many are beneficial, particularly the ones in the gut. However, several species of bacteria are pathogenic and cause infectious diseases, including cholera, syphilis, anthrax, leprosy, tuberculosis, tetanus and bubonic plague. The most common fatal bacterial diseases are respiratory infections. Antibiotics are used to treat bacterial infections and are also used in farming, making antibiotic resistance a growing problem. Bacteria are important in sewage treatment and the breakdown of oil spills, the production of cheese and yogurt through fermentation, the recovery of gold, palladium, copper and other metals in the mining sector (biomining, bioleaching), as well as in biotechnology, and the manufacture of antibiotics and other chemicals.

The word "murrain" /ˈmʌrɪn/ (like an archaic use of the word "distemper") is an antiquated term covering various infectious diseases affecting cattle and sheep. The word originates from Middle English moreine or moryne, in parallel to Late Latin morina ("plague"), a probable derivative of Latin mori ("to die").

The word "murrain", much like the word "pestilence", did not refer to a specific disease but rather served as an umbrella term for what veterinary science now recognises as a number of different diseases with high morbidity and mortality, such as rinderpest, erysipelas, foot-and-mouth disease, anthrax, and streptococcus infections. Some of these livestock diseases can also affect humans. The term "murrain" also referred to an epidemic of such a disease.

Heinrich Hermann Robert Koch (/kɒx/ KOKH; German: [ˈʁoːbɛʁt kɔx] ; 11 December 1843 – 27 May 1910) was a German physician and microbiologist. As the discoverer of the specific causative agents of deadly infectious diseases including tuberculosis, cholera and anthrax, he is regarded as one of the main founders of modern bacteriology. As such he is popularly nicknamed the father of microbiology (with Louis Pasteur), and as the father of medical bacteriology. His discovery of the anthrax bacterium (Bacillus anthracis) in 1876 is considered as the birth of modern bacteriology. Koch used his discoveries to establish that germs "could cause a specific disease" and directly provided proofs for the germ theory of diseases, therefore creating the scientific basis of public health, saving millions of lives. For his life's work Koch is seen as one of the founders of modern medicine.

While working as a private physician, Koch developed many innovative techniques in microbiology. He was the first to use the oil immersion lens, condenser, and microphotography in microscopy. His invention of the bacterial culture method using agar and glass plates (later developed as the Petri dish by his assistant Julius Richard Petri) made him the first to grow bacteria in the laboratory. In appreciation of his work, he was appointed to government advisor at the Imperial Health Office in 1880, promoted to a senior executive position (Geheimer Regierungsrat) in 1882, Director of Hygienic Institute and Chair (Professor of hygiene) of the Faculty of Medicine at Berlin University in 1885, and the Royal Prussian Institute for Infectious Diseases (later renamed Robert Koch Institute after his death) in 1891.

The Pasteur Institute (French: Institut Pasteur, pronounced [ɛ̃stity pastœʁ]) is a French non-profit private foundation dedicated to the study of biology, micro-organisms, diseases, and vaccines. It is named after Louis Pasteur, who invented pasteurization and vaccines for anthrax and rabies. The institute was founded on 4 June 1887 and inaugurated on 14 November 1888.

For over a century, the Institut Pasteur has researched infectious diseases. This worldwide biomedical research organization based in Paris was the first to isolate HIV, the virus that causes AIDS, in 1983. It has also been responsible for discoveries that have enabled medical science to control diseases such as diphtheria, tetanus, tuberculosis, poliomyelitis, influenza, yellow fever, and plague.

Biological agents, also known as biological weapons or bioweapons, are pathogens used as weapons. In addition to these living or replicating pathogens, toxins and biotoxins are also included among the bio-agents. More than 1,200 different kinds of potentially weaponizable bio-agents have been described and studied to date, and experts expect that in the future it will be possible to design novel biological weapons.

Some biological agents have the ability to adversely affect human health in a variety of ways, ranging from relatively mild allergic reactions to serious medical conditions, including serious injury, as well as serious or permanent disability or death. Many of these organisms are ubiquitous in the natural environment where they are found in water, soil, plants, or animals. Bio-agents may be amenable to "weaponization" to render them easier to deploy or disseminate. Genetic modification may enhance their incapacitating or lethal properties, or render them impervious to conventional treatments or preventives. Since many bio-agents reproduce rapidly and require minimal resources for propagation, they are also a potential danger in a wide variety of occupational settings.

Anthrax vaccines are vaccines to prevent the livestock and human disease anthrax, caused by the bacterium Bacillus anthracis.

They have had a prominent place in the history of medicine, from Pasteur's pioneering 19th-century work with cattle (the first effective bacterial vaccine and the second effective vaccine ever) to the controversial late 20th century use of a modern product to protect American troops against the use of anthrax in biological warfare. Human anthrax vaccines were developed by the Soviet Union in the late 1930s and in the US and UK in the 1950s. The current vaccine approved by the U.S. Food and Drug Administration (FDA) was formulated in the 1960s.  

Bacillus anthracis is a gram-positive and rod-shaped bacterium that causes anthrax, a deadly disease to livestock and, occasionally, to humans. It is the only permanent (obligate) pathogen within the genus Bacillus. Its infection is a type of zoonosis, as it is transmitted from animals to humans. It was discovered by a German physician Robert Koch in 1876, and became the first bacterium to be experimentally shown as a pathogen. The discovery was also the first scientific evidence for the germ theory of diseases.

B. anthracis measures about 3 to 5 μm long and 1 to 1.2 μm wide. The reference genome consists of a 5,227,419 bp circular chromosome and two extrachromosomal DNA plasmids, pXO1 and pXO2, of 181,677 and 94,830 bp respectively, which are responsible for the pathogenicity. It forms a protective layer called endospore by which it can remain inactive for many years and suddenly becomes infective under suitable environmental conditions. Because of the resilience of the endospore, the bacterium is one of the most popular biological weapons. The protein capsule (poly-D-gamma-glutamic acid) is key to evasion of the immune response. It feeds on the heme of blood protein haemoglobin using two secretory siderophore proteins, IsdX1 and IsdX2.

Bacillus cereus biovar anthracis is a variant of the Bacillus cereus bacterium that has acquired plasmids similar to those of Bacillus anthracis. As a result, it is capable of causing anthrax. In 2016, it was added to the CDC's list of select agents and toxins.

Bacillus cereus biovar anthracis infection has caused significant mortality in numerous mammalian species, including chimpanzees.

The Indian rhinoceros (Rhinoceros unicornis), also known as the greater one-horned rhinoceros, great Indian rhinoceros or Indian rhino, is a species of rhinoceros found in the Indian subcontinent. It is the second largest living rhinoceros species, with adult males weighing 2.07–2.2 t (2.04–2.17 long tons; 2.28–2.43 short tons) and adult females 1.6 t (1.6 long tons; 1.8 short tons). Its thick skin is grey-brown with pinkish skin folds. It has a single horn on its snout that grows up to 57.2 cm (22.5 in) long. Its upper legs and shoulders are covered in wart-like bumps, and it is nearly hairless aside from the eyelashes, ear fringes and tail brush.

The Indian rhinoceros is native to the Indo-Gangetic Plain and occurs in 12 protected areas in northern India and southern Nepal. It is a grazer, eating mainly grass, but also twigs, leaves, branches, shrubs, flowers, fruits and aquatic plants. It is a largely solitary animal, only associating in the breeding season and when rearing calves. Females give birth to a single calf after a gestation of 15.7 months. The birth interval is 34–51 months. Captive individuals can live up to 47 years. It is susceptible to diseases such as anthrax, and those caused by parasites such as leeches, ticks and nematodes.

Procaine benzylpenicillin also known as penicillin G procaine, is an antibiotic useful for the treatment of a number of bacterial infections. Specifically it is used for syphilis, anthrax, mouth infections, pneumonia, diphtheria, cellulitis, and animal bites. It is given by injection into a muscle.

Side effects include pain at the site of injection, blood clotting problems, seizures, and allergic reactions including anaphylaxis. When used to treat syphilis a Jarisch–Herxheimer reaction may occur. It is not recommended in those with a history of penicillin allergy or procaine allergy. Use during pregnancy and breastfeeding is relatively safe. Procaine benzylpenicillin is in the penicillin and beta lactam family of medications. It works via benzylpenicillin and results in bacterial death. Procaine makes the combination long acting.

The Homeland Security Act (HSA) of 2002 (Pub. L. 107–296 (text) (PDF), 116 Stat. 2135, enacted November 25, 2002) was introduced in the aftermath of the September 11 attacks and subsequent mailings of anthrax spores. The HSA was cosponsored by 118 members of Congress. The act passed the U.S. Senate by a vote of 90–9, with one Senator not voting. It was signed into law by President George W. Bush in November 2002.

HSA created the United States Department of Homeland Security and the new cabinet-level position of secretary of homeland security. It is the largest federal government reorganization since the Department of Defense was created via the National Security Act of 1947 (as amended in 1949). It also includes many of the organizations under which the powers of the USA PATRIOT Act are exercised.