98 Fun Facts About Microbiology

In 1796 Edward Jenner infected a boy with cowpox to protect him against which deadlier disease?

Smallpox: Latin vacca, 'cow', is why Jenner's cowpox method gave us the word vaccination.

In which Dutch city did Van Leeuwenhoek live and work for most of his life?

Delft: a cloth merchant there with no university education, he ground his own lenses and became the first person to see bacteria.

Robert Hooke coined the biological term 'cell' after studying thin slices of what?

Cork: the book reporting it, Micrographia, so gripped Samuel Pepys that he sat up until 2 a.m. reading it.

Lyme disease, a bacterial infection, is usually passed to people through the bite of what?

Ticks: the illness takes its name from Lyme, Connecticut, where a mysterious cluster of cases in 1975 led doctors to identify it.

Tetanus is often blamed on rusty nails, but what actually causes it?

Bacteria from soil: rusty nails are simply outdoor objects that tend to carry dirt, and deep, dirty wounds give the germs their best chance.

Louis Pasteur's famous flask experiments were designed to disprove which theory?

Spontaneous generation: his swan-necked flasks let air in but trapped falling dust, so the boiled broth stayed free of microbes for months.

Pasteurization is best known for milk, but Louis Pasteur first developed it to stop which drink spoiling?

Wine: he showed that unwanted microbes caused wine's 'diseases' and that gentle heating destroyed them, and the method reached milk only later.

Before giving his rabies vaccine to a bitten boy in 1885, Louis Pasteur had tested it on which animals?

Dogs: he had protected dogs even after they were bitten, and the boy's recovery helped bring in public donations for the Institut Pasteur.

In 1876 Robert Koch gave the first proof that a specific bacterium causes which disease?

Anthrax: he did it as a country doctor working in his own four-room flat, with a microscope his wife had given him.

World TB Day falls on 24 March because on that date in 1882 Robert Koch announced what?

The bacterium behind TB: the 'cure' Koch later promoted, tuberculin, was hoped to heal the disease but proved ineffective.

How many criteria make up Koch's postulates for linking a microbe to a disease?

They were formulated with Friedrich Loeffler in 1884 and refined by Koch in 1890; modified versions now exist for prions.

The shallow lidded dish used to culture microbes is named after which assistant of Robert Koch?

Julius Richard Petri: Koch's team had been covering their plates with heavy bell jars to keep out dust, until Petri simply added a slightly larger glass lid.

Agar, the jelly Fanny Hesse is credited with suggesting for growing bacteria, is made from what?

Seaweed: unlike the gelatin used before, agar stays solid at the warm temperatures where bacteria grow best.

The Gram stain was devised in Berlin in 1884 by Hans Christian Gram, a scientist of which nationality?

Danish: his first report modestly called the method 'very defective and imperfect', yet it is still a standard first step in identifying bacteria.

In a Gram stain, Gram-positive bacteria retain which primary dye?

Crystal violet: iodine locks the purple dye inside thick cell walls, while thin-walled gram-negative cells lose it to an alcohol wash and turn pink.

Bacterial cell walls are made of which polymer, absent from archaea?

Peptidoglycan: this mesh-like wall is what penicillin attacks, damaging it until the bacterium is destroyed.

Spherical bacteria are called cocci, so what are rod-shaped bacteria called?

Bacilli: Latin for 'little staffs', and the word bacteria itself comes from Greek for a small staff, because the first ones seen were rods.

Which part of our cells, about the size and shape of a bacterium, is thought to have begun as one?

The mitochondrion: one clue is its own small set of DNA, which looks more like a bacterium's than like the DNA in our nucleus.

Thiomargarita magnifica, described in 2022 as the largest known bacterium, typically grows to about what length?

1 centimetre: big enough to see by eye, it also wraps its DNA in membrane sacs, unlike the loose DNA of most bacteria.

Under ideal conditions, roughly how quickly can E. coli reproduce?

Every 20 minutes: at that pace a single cell could, in theory, become over two million bacteria in just seven hours.

Which pediatrician discovered E. coli in the faeces of healthy people in 1885?

Theodor Escherich: studying babies' gut bacteria, he found it in sick and healthy children alike, and the genus Escherichia was later named in his honour.

Which DNA sequence is the standard molecular tool for identifying bacteria?

The 16S rRNA gene: comparing it is how Carl Woese and George Fox showed in 1977 that archaea are a separate line of life, not bacteria.

Archaea living in the digestive tracts of cows produce which gas?

Methane: a potent greenhouse gas, which is why livestock are counted with fossil fuels and landfills in tallies of its emissions.

An enzyme from a heat-loving bacterium found in hot springs made which DNA technique practical?

PCR: its enzyme survives the near-boiling heat of each cycle, so scientists no longer had to add fresh enzyme again and again.

The first virus ever identified, in the 1890s, infects which plant?

Tobacco: in 1898 Martinus Beijerinck confirmed that the germ slipped through filters that trap bacteria, yet it multiplied inside living plants.

The word 'virus' comes from a Latin word meaning what?

Poison: English doctors long used 'virus' for poisonous or infectious matter, and only pinned it on these tiny germs once they were discovered in the 1890s.

Bacteriophages, viruses that infect bacteria, take their name from a Greek word meaning what?

To devour: d'Herelle's 'bacterium-eaters' were soon put to work as medicine, and from the 1920s to the 1940s phage therapy treated many infections.

Alexander Fleming discovered which enzyme after putting his own nasal mucus onto a dish of bacteria?

Lysozyme: it attacked only a few harmless kinds of bacteria, so it had little use as a medicine.

Ignaz Semmelweis cut childbed fever deaths in 1847 by insisting doctors do what?

Wash their hands in chlorinated lime: his doctors and students came to deliveries straight from autopsies, while the midwives' clinic, which did none, saw far fewer deaths.

Joseph Lister pioneered antiseptic surgery in Glasgow using which chemical?

Modern-day phenol; he used it on instruments, sutures, wounds and surgeons' hands.

Before germ theory, the leading medical theory blamed diseases such as cholera on what?

Bad air, or miasma: the belief lives on in the word malaria, from the Italian for 'bad air', once blamed for that fever.

Barry Marshall proved Helicobacter pylori causes gastritis by doing what?

Drinking a culture of the bacterium gave him stomach inflammation within days, and ulcers are now cured with a short course of antibiotics.

A 2016 estimate found the bacteria living in a person's body roughly match the number of what?

Your own human cells: about 38 trillion bacteria to 30 trillion of our cells, busting the decades-old claim that bacteria outnumber us ten to one.

Deinococcus radiodurans, famed for surviving huge doses of radiation, has which nickname?

Conan the Bacterium: it was discovered in 1956 in a tin of meat that spoiled even though radiation should have sterilised it.

Prochlorococcus was described in a 2015 review as the most abundant what on Earth?

Photosynthetic organism: though far too small to see, these ocean cells make a large share of the oxygen in our biosphere.

What are the dormant, centuries-surviving structures formed by Bacillus and Clostridium bacteria called?

One report describes viable Bacillus spores in salt crystals about 25 million years old.

In 2019 the crashed Israeli lunar lander Beresheet may have spilled which tough micro-animals onto the Moon?

Tardigrades: they were added at the last minute, dried out and sealed in resin inside a small archive of human knowledge.

Baker's and brewer's yeast, which turns sugars into carbon dioxide and alcohol, is which species?

Saccharomyces cerevisiae: Louis Pasteur showed that fermentation is the work of living yeast cells, not simply a chemical reaction.

The tuberculosis bacterium resists the Gram stain because of a waxy coat rich in what?

Mycolic acid: the waxy coat holds on to dye even after an acid wash, which is why TB is detected with an 'acid-fast' stain instead.

Which of these is a sub-discipline of microbiology concerned with fungi?

Mycology: it was long treated as a branch of botany, but fungi turned out to be more closely related to animals than to plants.

Which ancient Indian religion teaches its monks and nuns to wear face masks to avoid breathing in tiny living things?

Jainism: out of the same care for the smallest lives, its monks and nuns gently sweep the path ahead so they don't step on insects.

What are the infectious proteins that cause diseases such as BSE called?

Prions: they resist ordinary disinfection, and a few people have caught CJD from contaminated brain-surgery instruments.

What usually causes a 'red tide' in coastal waters?

An algal bloom: its toxins can make shellfish unsafe to eat, which is why states closely monitor the shellfish that fishermen harvest.

Mary Mallon, a New York cook who infected others without ever feeling ill, carried which disease?

Typhoid fever: after she went back to cooking, officials confined her on an island for the last 23 years of her life.

Robert Koch's 1883-84 cholera investigation in Egypt and India tied the disease's spread to what?

Contaminated water: yet the cholera germ itself had already been described in 1854, by the Italian researcher Filippo Pacini.

Microscope pioneer Antonie van Leeuwenhoek was appointed trustee of which painter's estate?

Johannes Vermeer: the painter died deep in debt, so a trustee had to deal with his creditors.

Antonie van Leeuwenhoek sent letters about what he saw through his one-lens microscopes to which scientific body?

The Royal Society: he could write to it only in his native Dutch, yet it published many of his letters in its journal.

Ireland's Great Famine of the 1840s was caused by which potato disease?

Late blight: it hit potatoes across Europe, but Ireland suffered worst because so many people depended on potatoes for most of their food.

A single honey fungus spreading under more than 2,000 acres of forest in which US state may be Earth's largest organism?

Oregon is home to the 'humongous fungus', an Armillaria colony covering more than three square miles of Malheur National Forest. The mushrooms seen above ground are only its fruiting tips.

The fungus Ophiocordyceps unilateralis turns which insects into 'zombies' that clamp onto leaves before dying?

Ants infected by the fungus leave their nests, bite into the underside of a leaf and die there, in a spot that suits the fungus. Alfred Russel Wallace discovered it in 1859.

The Black Death was caused by Yersinia pestis, a bacterium spread mainly by the bites of which insects?

Fleas living on black rats most likely carried the plague from Crimea aboard Genoese ships. Once ashore it may also have passed straight from person to person as a lung infection.

Toxoplasma gondii, a parasite carried by up to half of all people, can reproduce sexually only inside which animals?

Cats are the parasite's only definitive hosts. Infected rodents behave in ways that make them easier prey, which carries the parasite back to the one place it can breed.

Salmonella bacteria are named not after the fish but after Daniel Salmon, an American in which profession?

Veterinarian Daniel Salmon headed the veterinary division of the US Department of Agriculture. His assistant Theobald Smith actually isolated the first strain in 1885.

Which mammals of the southern United States can carry the leprosy bacterium and pass it to people who handle them?

Armadillos are among the few mammals besides humans that catch leprosy. They are thought to have picked it up from early European explorers of the Americas and kept it circulating.

The chickenpox virus can lie dormant in nerve cells for decades and then return as which painful, blistering rash?

Shingles appears when the dormant virus reawakens and travels along a nerve to the skin. Someone with the rash can give chickenpox, but not the rash itself, to a person who never had it.

The 1918 flu pandemic is misleadingly named after which neutral country, whose uncensored newspapers reported it freely?

Spain had no wartime censors, so its papers covered the outbreak while the warring nations hushed it up. The pandemic did not start there, and Spaniards called it the French flu.

The so-called brain-eating amoeba Naegleria fowleri, found in warm fresh water, infects people by entering through what?

The nose is its only way in: the amoeba follows the smell nerves up to the brain when water is forced into the nostrils. Swallowing the same water causes no infection.

Which disease is caused by single-celled Plasmodium parasites carried between people by female Anopheles mosquitoes?

Malaria comes from a parasite, not a virus or bacterium. Only female mosquitoes pass it on, because only they feed on blood, which they need to develop their eggs.

Which highly contagious viral disease produces tiny white Koplik spots inside the mouth before its red rash spreads?

Measles is one of the most contagious human diseases: where nobody is immune, a single case typically infects 12 to 18 other people.

Which American virologist developed the polio vaccine that came into use in 1955 and was never patented?

Jonas Salk was hailed as a miracle worker when the vaccine's success was announced. Asked on television who owned the patent, he said it belonged to the people.

Coronaviruses take their name from the Latin word for what, after the fringe of spikes seen around each particle?

Crown, or wreath, is what the Latin 'corona' means. Under an electron microscope the spikes form a halo around each particle, much like the corona of the Sun.

The Ebola virus, first identified in 1976, takes its name from what in the Democratic Republic of the Congo?

A river near the village of Yambuku, where one of the first known outbreaks struck, gave the virus its name. A second outbreak was unfolding at the same time in what is now South Sudan.

More than 160 known types of which virus group are the most frequent cause of the common cold?

Rhinoviruses cause at least half of all colds. Immunity to one type gives little protection against the rest, which is the main obstacle to making a vaccine.

Nearly all cervical cancer is caused by which virus, the target of a vaccine offered mainly to girls aged 9 to 14?

Human papillomavirus comes in many strains, but just two of them, HPV16 and HPV18, account for about 70% of cervical cancer cases.

Doctors stage an HIV infection by counting which type of white blood cell, the virus's main target, in a blood sample?

Helper T cells carry the CD4 protein on their surface, so the test is called a CD4 count. A fall below 200 per microlitre of blood marks the onset of AIDS.

In flu strain names such as H1N1, the H stands for haemagglutinin and the N for which other surface protein?

Neuraminidase is the enzyme that cuts newly made flu particles free from an infected cell. Antiviral drugs such as oseltamivir (Tamiflu) work by jamming it.

Rinderpest, declared eradicated in 2011 after a long vaccination campaign, was a viral plague mainly of which animals?

Cattle gave the disease its German name, which means 'cattle plague'. It is only the second disease in history to be wiped out completely.

Scarlet fever, known for its red rash and 'strawberry tongue', is caused by bacteria of which genus?

Streptococcus pyogenes causes the rash only when it carries a toxin gene delivered by a virus that infects bacteria. Without it, the same germ gives an ordinary sore throat.

MRSA, a notorious 'superbug', is a strain of Staphylococcus aureus that resists which antibiotic, the M in its name?

Methicillin was developed in 1959, and the first strains able to resist it were reported in Britain just two years later.

Legionnaires' disease is named after a 1976 outbreak at an American Legion convention held in which city?

Philadelphia was hosting the veterans at the Bellevue-Stratford Hotel when a mystery pneumonia began killing them. The bacterium responsible, unknown until then, was identified the following January.

Pertussis, a bacterial infection that is most dangerous to babies, is better known by which everyday name?

Whooping cough is named after the high-pitched gasp that follows a coughing fit. The fits can last ten weeks or more, which is why it is also called the 100-day cough.

Which food-borne bacterium, a hazard in soft cheeses and deli meats, can keep multiplying at refrigerator temperatures?

Listeria can grow at temperatures as low as 0 °C, so chilling food slows it without stopping it. Most other food-poisoning bacteria survive in the cold but cannot multiply there.

Rhizobium bacteria living in swellings on the roots of peas and beans supply the plants with which element?

Nitrogen makes up most of the atmosphere, but plants cannot use it as a gas. The bacteria in the root nodules convert it into ammonia with an enzyme called nitrogenase.

Cyanobacteria transformed Earth's atmosphere more than two billion years ago by releasing which gas as a waste product?

Oxygen was toxic to most of the life that existed at the time. Its build-up, known as the Great Oxidation Event, may have caused a mass extinction among early microbes.

Yogurt gets its tart flavour and thick texture when bacteria ferment the sugars in milk into what?

Lactic acid acts on the milk proteins as it builds up, which is what thickens yogurt. The same kind of fermentation makes sauerkraut and kimchi.

Paul Ehrlich's 'magic bullet' Salvarsan, launched in 1910, was the first effective drug treatment for which disease?

Syphilis was the target of the arsenic-based drug, known in Ehrlich's laboratory as compound 606. It remained the standard treatment until penicillin replaced it in the 1940s.

Fungi stiffen their cell walls with which tough polymer, also found in the shells of insects and crabs?

Chitin is one of the traits that put fungi in a different kingdom from plants, whose cell walls are built from cellulose. It also forms the beaks of squid and octopuses.

LSD was first made in 1938 from compounds found in ergot, a fungus whose most common host is which cereal?

Rye bread tainted with ergot caused medieval outbreaks of 'Saint Anthony's fire', which brought gangrene, convulsions and hallucinations.

Which itchy skin infection is caused by a fungus, despite a name that suggests a burrowing parasite?

Ringworm takes its misleading name from the ring-shaped red patches it leaves on the skin. Athlete's foot and jock itch are the same kind of infection in other places.

African sleeping sickness is caused by single-celled trypanosomes injected by the bite of which blood-feeding insect?

Tsetse fly bites inject the parasites, which weeks or months later cross into the brain. The confusion and disturbed sleep that follow give the disease its name.

Which water-borne parasite has been the target of an eradication campaign spearheaded by the Carter Center since 1986?

Guinea worm infected an estimated 3.5 million people a year when the campaign began. With no vaccine or medicine against it, the effort relies on filtering the water people drink.

Giardiasis, a gut infection caught by campers who drink untreated water, is nicknamed which animal's 'fever'?

Beaver fever is a misleading nickname twice over: only about 15% of patients run a fever, and pets, sheep and many other animals carry the parasite as well.

Physarum polycephalum, which can find the shortest route through a maze, is what kind of brainless organism?

A slime mould is one giant cell with many nuclei. In a 2010 experiment, oat flakes were laid out like Tokyo and 36 nearby towns, and it linked them with an efficient network.

Diatoms, tiny algae whose fossil remains form diatomaceous earth, build their ornate shells from what?

Silica, the raw material of glass, forms a shell of two halves around each diatom. The fossil deposits are used in water filters, as a mild abrasive and to stabilise dynamite.

Panama disease, a fungal wilt, all but wiped out commercial plantings of which banana variety during the 1950s?

Gros Michel supplied almost the whole export trade until the fungus struck, forcing growers to switch to the resistant Cavendish. A later strain attacks Cavendish too.

The chytrid fungus Batrachochytrium dendrobatidis is blamed for the decline of over 500 species of which animals?

Amphibians catch the fungus through their skin, where it attacks the outer layers. A 2019 review counted 90 species confirmed or presumed extinct in the wild because of it.

Which word did English translations of Antonie van Leeuwenhoek's Dutch letters use for the microbes he had seen?

Animalcules, from the Latin for 'little animals', was the translator Henry Oldenburg's rendering of Dutch words such as 'dierkens'. Most of them were what we now call single-celled organisms.

Which Y-shaped proteins does the immune system make to recognise and lock onto one specific germ or toxin?

Antibodies each recognise one particular target, known as an antigen. That word joins 'anti(body)' to the ending '-gen', marking a substance that generates antibodies.

What is the general term, built from Greek words for 'suffering' and 'producer', for any microbe that causes disease?

Pathogen is a broad label that covers viruses, bacteria, fungi and protozoa alike. The word only came into use in the 1880s.

What is the term for an infectious disease, such as rabies or Ebola, that passes from animals to humans?

Zoonosis is how roughly 60% of known human infectious diseases began, along with up to 75% of newly emerging ones.

Which animals are natural hosts of the Marburg, Nipah and Hendra viruses, all of which can spread to people?

Bats are also the suspected original source of the SARS and MERS viruses, although camels are thought to pass MERS on to people.

The five different hepatitis viruses, labelled A to E, all cause inflammation of which organ?

The liver can carry hepatitis B or C for years without symptoms. These long-lasting infections are a major cause of cirrhosis and liver cancer.

Which gene-editing tool was adapted from a defence system that bacteria use to chop up the DNA of invading viruses?

CRISPR began as a kind of immune memory: bacteria keep fragments of a virus's DNA so they can recognise and cut it next time. The editing technique won the 2020 Nobel Prize in Chemistry.

Glowing bacteria such as Aliivibrio fischeri switch on their light only at high numbers, using which signalling process?

Quorum sensing lets each cell judge how crowded it is from chemical signals its neighbours release. Aliivibrio fischeri uses it to light up an organ inside the Hawaiian bobtail squid.

Mosquitoes are deliberately infected with which bacterium, common in other insects, to stop them spreading dengue?

Wolbachia makes it harder for the virus to multiply inside the insect, and mothers hand it down through their eggs. City-wide releases began in Townsville, Australia, in 2014.

Faecal microbiota transplants are an effective treatment for recurring gut infections with which bacterium?

C. difficile tends to take hold after antibiotics kill off its competitors in the gut. A transplant of donor microbes works in about 85–90% of cases where more antibiotics have failed.

A disease that is constantly present at a steady level in one region is described as what?

Endemic says nothing about how severe a disease is, only that the number of cases stays predictable. A usually steady disease that suddenly surges becomes an epidemic.

The densest community of microbes found anywhere in or on the human body lives in which organ?

The colon holds between 300 and 1,000 different species, nearly all of them microbes that live without air.