110 Fun Facts About Bacteria

The word 'bacterium' comes from an Ancient Greek word meaning what?

The first ones discovered were rod-shaped, hence the walking-stick image; the spherical kind got a separate word meaning 'grain'.

Bacteria are prokaryotes. Which of these do their cells lack?

Their single circular chromosome sits in an irregular region of the cytoplasm called the nucleoid.

Roughly how many bacteria are thought to exist on Earth?

Their combined biomass is exceeded only by that of plants.

Comma-shaped or slightly curved rod bacteria are known by what name?

The cholera bacterium is the classic vibrio; Robert Koch described it as 'a little bent, like a comma'.

Staphylococci group together in clusters likened to what?

The name itself comes from the Greek for 'grape-cluster berry'; streptococci, by contrast, form chains.

Bacterial cell walls are made of which polymer, which penicillin stops them building?

Plants use cellulose and fungi use chitin, which is why penicillin harms neither.

In a Gram stain, what colour do Gram-negative bacteria appear?

The thick walls of Gram-positive cells hold the purple dye; thin-walled Gram-negatives lose it and take up the pink counterstain.

Inhaling the endospores of which bacterium causes anthrax?

Clostridium tetani spores in deep puncture wounds cause tetanus in much the same way, and both illnesses come from toxins the germinated cells release.

Bacteria reproduce asexually by splitting in two. What is this process called?

Some populations can double as quickly as every 17 minutes.

When bacteria enter a fresh nutrient-rich medium, what is the first stage of growth called, before rapid division begins?

The cells spend it building the proteins they need for the exponential burst that follows.

The transfer of DNA between two bacteria through direct cell contact via a pilus is called what?

Transformation is taking up loose DNA from the environment, and transduction is delivery by a virus.

Which small extra-chromosomal DNA molecules often carry antibiotic-resistance genes in bacteria?

They can hop between species by horizontal gene transfer, which is how resistance spreads.

Bacteria keep fragments of past viral invaders' genomes as an immune memory in which system, later turned into a gene-editing tool?

The 2020 Nobel Prize in Chemistry went to Charpentier and Doudna for turning this bacterial defence into genetic scissors.

A bacterium with a single flagellum is described by which term?

Peritrichous cells such as E. coli are covered all over, which lets them alternate swimming with tumbling.

The bacterial flagellum is built from roughly how many different proteins?

Around another 30 proteins are needed just to assemble and regulate it, all powering a rotary motor at the base.

Bacteria that decide to act only when their population is dense enough use which signalling process?

It controls things like glowing or secreting digestive enzymes that only pay off in a crowd.

Bacteria in biofilms can be how much more resistant to antibacterial agents than free-floating cells of the same species?

This is why infections on implanted devices such as catheters are so hard to clear.

Bacteria that swim along Earth's magnetic field lines contain crystals of which iron mineral inside organelles called magnetosomes?

Some species make greigite, an iron sulphide, instead; the chains of crystals act as a compass needle.

Magnetotactic bacteria were first noticed in 1963 by which Italian, whose work was forgotten until Richard Blakemore rediscovered them in 1975?

Blakemore's paper in Science did not mention him, and Blakemore's term 'magnetotaxis' is the one that stuck.

Which group of bacteria is credited with the Great Oxidation Event, the first flood of free oxygen into Earth's atmosphere?

The same lineage was later swallowed by early eukaryotes and became the chloroplasts of algae and plants.

Which health-food supplement is actually a bacterium, not a true alga, sold as food?

Chlorella and nori are true algae; the supplement's producer was long placed in the genus Arthrospira.

Which layered rock mounds built by microbes still grow at Shark Bay in Western Australia?

They peaked about 1.25 billion years ago and were probably grazed into decline once complex animals appeared.

Which soil bacteria, famous for the earthy smell of rain, produce over two-thirds of clinically useful natural antibiotics?

The smell comes from geosmin, a volatile compound they release, and streptomycin takes its name from them.

Which glowing bacterium lights up the light organ of the Hawaiian bobtail squid?

The two-species partnership is the textbook model for how bacteria count their neighbours, since they glow only when packed densely enough.

Wolbachia, a bacterium that manipulates insect reproduction, has been released into mosquitoes to suppress which disease?

After infected mosquitoes were released in Townsville, Australia, in 2014, the city reported no cases for four years.

Roughly what share of all insect species are estimated to be potential hosts of Wolbachia?

In some woodlice it feminises males so thoroughly that populations have lost their female-determining chromosome.

Yersinia pestis, the plague bacterium, was isolated in 1894 during an epidemic in which city?

Alexandre Yersin and Kitasato Shibasaburō found it independently within days of each other; Yersin got the naming rights.

Before it got its modern name in 1944, what did Yersin call the plague bacillus in honour of his institute?

Its main vector is the oriental rat flea, though the pneumonic form spreads by airborne droplets.

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

The disease was first traced to spoiled blood sausages in Württemberg in the early 1800s.

Which Belgian microbiologist discovered Clostridium botulinum in 1895 after a fatal outbreak at a funeral where guests ate pickled ham?

Justinus Kerner's 1817-22 descriptions of the illness had already suggested the toxin might be useful medically.

Barry Marshall and Robin Warren won the 2005 Nobel Prize for showing that a bacterium causes which condition?

German scientists had spotted spiral bacteria in the stomach lining as early as 1875 but nobody followed it up.

Roughly what fraction of the world's population is estimated to be infected with Helicobacter pylori?

Most people never have symptoms; the helical body and flagella help it corkscrew into the stomach's mucus lining.

The species name of Staphylococcus aureus is Latin for what colour?

The colour comes from a carotenoid pigment called staphyloxanthin; colonies on blood agar look golden-yellow.

Which Scottish surgeon discovered in 1880 that staphylococci cause wound infections, after seeing them in pus from an abscess?

Fleming's famous mouldy Petri dish, decades later, was growing a culture of the same bacterium.

Which Italian first identified the cholera bacterium in 1854, thirty years before Robert Koch's rediscovery made it famous?

His name survives in the organism's formal designation; the toxin itself was only isolated in Calcutta in 1959.

Cholera toxin is not encoded directly by the bacterium's own genes. What carries the toxin genes?

The virus, CTXphi, only switches the toxin on once it has inserted into the bacterial chromosome.

Theodor Escherich first named the bacterium now called E. coli 'Bacterium coli commune' in 1885. Why 'coli'?

He found it in the faeces of healthy people; the genus was later renamed in his honour.

One of the first commercial uses of recombinant DNA was engineering E. coli to make which human hormone?

Bacteria are the workhorses of biotech because they grow fast and are easy to manipulate.

Which vitamin does E. coli produce for its host in the gut?

It also crowds out harmful pathogens trying to colonise the intestine.

Nearly all animal life depends on bacteria because only they (and some archaea) can synthesise which vitamin?

It travels up the food chain and is essential for the myelin that insulates human nerves.

Which two bacteria are the standard pair used to ferment milk into yogurt?

France only allows the label 'yaourt' if those two alone did the fermenting.

Which Nobel laureate suggested that yogurt explained the long lives of Bulgarian peasants, sparking a craze for it in the West?

He was building on the work of Stamen Grigorov, a Bulgarian medical student who first studied the yogurt's microflora.

Bacillus thuringiensis, sold under names like Dipel, is used in farming as what?

It targets caterpillars specifically and is considered harmless to pollinators and people.

After which 1989 disaster was fertiliser spread on beaches to boost oil-eating bacteria?

The technique worked on beaches that were not too thickly coated in crude.

Who introduced the word 'bacterium' in 1828, originally as a genus of non-spore-forming rods?

Seven years later he defined Bacillus for the spore-forming rods.

Before they were classed as prokaryotes, bacteria were lumped into the plant kingdom under what name meaning 'fission fungi'?

That botanical hangover is why the microbes living in a host are still called 'flora'.

Because Antonie van Leeuwenhoek's lenses were at the very limit of what could resolve bacteria, roughly how long passed before anyone else saw them again?

He reported them to the Royal Society in letters and lumped everything he saw together as 'animalcules'.

Which of these bacterial diseases is caused by a Rickettsia species that can only grow inside other cells?

Another Rickettsia causes Rocky Mountain spotted fever; both are spread by arthropods.

Which of these is among the smallest bacteria, at about 0.3 micrometres, as small as the largest viruses?

At the other extreme, Thiomargarita magnifica reaches 2 centimetres, visible without a microscope.

How many bacterial cells are there in a cubic metre of ordinary air?

Ocean bacteria, meanwhile, supply up to half of the oxygen humans breathe.

The oceans' bacteria are estimated to provide up to what share of the oxygen humans breathe?

The seas hold around 3 x 10^26 bacteria, and only about 2% of bacterial species have been fully studied.

Which enzyme lets nitrogen-fixing bacteria such as rhizobia turn atmospheric nitrogen into a form plants can use?

Legumes house them in root nodules, which is why farmers rotate crops with beans and clover.

Myxobacteria that are starved of amino acids swarm together into fruiting bodies containing roughly how many cells?

About one in ten cells climbs to the top and turns into a tough dormant myxospore.

The bacterium with the smallest known genome, Carsonella ruddii, has a chromosome of only about how many base pairs?

It lives inside insects, which supply much of what it can no longer make for itself; soil bacteria can carry 100 times more DNA.

Human mitochondria are descended from which group of bacteria that were engulfed by early cells?

Chloroplasts came later, from a separate swallowing of photosynthetic bacteria.

The gas vacuoles that let blue-green algae float up and down in a lake control what?

That is how summer blooms park themselves at the light level and nutrient layer they like.

Which giant bacterium can reach 2 cm in length, about 50 times larger than other known bacteria?

Its relative Thiomargarita namibiensis reaches half a millimetre, already visible to the naked eye.

Which scientist recognised in 1977 that archaea have a separate line of descent from bacteria?

His insight underpins the three-domain system of Bacteria, Archaea and Eukarya used in microbiology today.

In 1910 Paul Ehrlich created the first antibiotic by modifying dyes that stained which pathogen?

The spirochaete causes syphilis; the resulting drug, Salvarsan, was arsenic-based.

For proving the germ theory through his research into which disease did Robert Koch win the 1905 Nobel Prize?

Koch's postulates, his criteria for showing an organism causes a disease, are still used today.

Which famous shipwreck is slowly being eaten by a rust-making bacterium that is named after it?

Titanic rusticles, icicle-like growths hanging from the wreck, yielded the new species Halomonas titanicae in 2010. The microbes ingest iron from the ship and leave rust behind as waste.

In Operation Sea-Spray, the US Navy secretly sprayed bacteria over which city to mimic a germ attack?

San Francisco was misted from a ship offshore in 1950, and monitors suggested nearly all of its 800,000 residents inhaled the particles. The Army disclosed the tests at Senate hearings in 1977.

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

Armadillo meat and bare-handed contact are both routes of infection. Armadillos are thought to have caught the disease from early European explorers of the Americas.

The sled-dog relay to Nome, Alaska, that made the husky Balto famous carried antitoxin for which bacterial disease?

Diphtheria antitoxin crossed 674 miles in five and a half days, passed between 20 mushers and about 150 dogs. Another dog, Togo, led the longest and most dangerous stretch.

Which wrinkle-smoothing brand is a bacterial nerve poison considered the deadliest natural substance known?

Botox is a purified toxin from Clostridium botulinum that stops nerves telling muscles to contract. The frown lines it relaxes typically stay smooth for two to four months.

Which sweet food should babies under one never be fed because it can carry dangerous bacterial spores?

Honey is a known reservoir of Clostridium botulinum spores. In a baby's intestines the bacterium can grow and release its toxin, causing what doctors call floppy baby syndrome.

The microbe nicknamed 'Conan the Bacterium' was named by Guinness as the life form most resistant to what?

Radiation a thousand times the dose that can kill a human leaves Deinococcus radiodurans almost unharmed. It was first found in a tin of meat that spoiled after supposedly sterilising gamma rays.

A bacterium found at a bottle-recycling site in Sakai, Japan, made headlines for digesting which material?

Plastic of the PET kind used in drinks bottles is this microbe's food. Two enzymes working in sequence break it down, and the pieces supply the cell with carbon and energy.

Mary Mallon, an Irish-born New York cook who showed no symptoms herself, infamously spread which bacterial disease?

Typhoid fever followed Mallon from kitchen to kitchen until officials forcibly quarantined her on North Brother Island in the East River. Health officials nicknamed her Typhoid Mary.

Which blood-sucking parasites carry the plague bacterium from rats and other small mammals to people?

Fleas that swallow the microbe end up with a blocked gut, so when they next try to feed they regurgitate bacteria straight into the wound. The Oriental rat flea is the classic carrier.

Which tick-borne bacterial illness is named after a Connecticut town where children developed puzzling arthritis?

Lyme disease was recognised in 1975, when a cluster of children in Lyme and Old Lyme seemed to have juvenile rheumatoid arthritis. Its spiral bacterium was named Borrelia burgdorferi in 1982.

The holes in Swiss cheeses such as Emmental are bubbles of which gas, given off by bacteria as the cheese ripens?

Carbon dioxide from Propionibacterium freudenreichii collects into the bubbles cheesemakers call eyes. The bubbles start around microscopic specks of hay dust that get into the milk.

Which scientist returned from a holiday to find mould killing the bacteria on a culture plate he had left out?

Alexander Fleming had left plates of staphylococci on a bench before a family break in Suffolk in 1928. He shared the 1945 Nobel Prize with Howard Florey and Ernst Chain for the discovery and its power to cure infections.

Thermus aquaticus, the heat-loving bacterium whose enzyme powers PCR tests, was first found in which national park?

Yellowstone's Mushroom Spring yielded the microbe, reported in 1969. Its Taq polymerase survives the near-boiling steps of PCR, so fresh enzyme no longer has to be added after every heating cycle.

Which common skin condition is linked to a bacterium that lives deep in hair follicles and feeds on oily sebum?

Acne flares when a blocked follicle or a surge of sebum lets Cutibacterium acnes multiply. The same microbe also lives quietly on the surface of healthy skin.

Which fizzy fermented tea is brewed with a rubbery floating mat of bacteria and yeast known as a SCOBY?

Kombucha's mat is often called a mushroom, but it is really a growth of acetic acid bacteria and yeast. The yeast makes alcohol from the sugar, and the bacteria turn it into tangy acid.

Stubborn gut infections with Clostridioides difficile bacteria are treated by transplanting what from a healthy donor?

Stool from a healthy person restores the gut microbes a patient has lost, and it works in about 90 percent of severe cases. Chinese medicine recorded the idea some 1,700 years ago.

Which structures in plant cells descend from free-living photosynthetic bacteria engulfed by an early cell?

Chloroplasts kept their own DNA as a relic of their free-living past. With one known exception, every chloroplast on Earth traces back to a single swallowing event.

Measured by carbon, the bacteria on Earth outweigh which entire kingdom of life more than thirty times over?

Animals, from insects to whales, hold only about 0.4% of the carbon in living things, against roughly 13% for bacteria. Only the plant kingdom, at more than 82%, outweighs the microbes.

Salmonella bacteria have nothing to do with fish: the name honours Daniel Salmon, an American in which profession?

Veterinarian Daniel Salmon earned the first DVM degree granted in the United States. The germ named in his honour was actually discovered by his research assistant, Theobald Smith.

Rhizobia, soil bacteria that capture nitrogen from the air, make their home in root swellings of which plant family?

Legumes such as peas, beans and clover feed the microbes carbohydrates and get usable nitrogen in return. Some of it stays in the soil, which is why farmers use them in crop rotation.

Cows cannot digest the cellulose in grass themselves, so bacteria do it for them in which chamber of the gut?

Rumen bacteria make enzymes called cellulases that split the tough fibre. Further along the gut, the cow goes on to digest the bacteria themselves.

Sauerkraut keeps for months because bacteria turn the sugars in cabbage leaves into which sour preservative?

Lactic acid gives sauerkraut both its sour flavour and its long shelf life. Captain James Cook took the fermented cabbage on his sea voyages to prevent scurvy.

Which sticky, stringy Japanese food is made by fermenting whole soybeans with bacteria once sourced from rice straw?

Natto was historically wrapped in rice straw, which supplied the microbe, until a starter culture made the straw unnecessary around the 1910s. Stirring it draws out long sticky strings.

Which disease, caught when soil bacteria enter a cut or puncture wound, is nicknamed lockjaw?

Tetanus has nothing to do with rust itself: a rusty nail is just a dirty object that drives soil bacteria deep into the body. The first spasms usually strike the jaw muscles.

Legionnaires' disease takes its name from a deadly outbreak at an American Legion convention in which city?

Philadelphia's Bellevue-Stratford Hotel hosted the 1976 gathering, where 29 of the 182 people infected died. The newly found bacterium thrives in hot water tanks and air-conditioning cooling towers.

Bacteria known as cocci, including the staphylococci and streptococci, have which basic shape?

Spherical bacteria can stay attached after dividing, so they turn up in pairs, chains, clusters or flat squares of four called tetrads.

Unlike the linear chromosomes in human cells, the single chromosome of most bacteria takes which form?

Circular DNA has no loose ends, so bacteria can do without the telomeres that human cells need to keep the tips of their chromosomes stable.

English translations of Antonie van Leeuwenhoek's letters used which word for the bacteria and tiny creatures he saw?

Animalcules was the word Henry Oldenburg chose when translating the Dutch letters. Leeuwenhoek found the creatures everywhere he looked, including on his own teeth.

Which piece of lab equipment is named after the assistant of Robert Koch who perfected it?

Petri dish inventor Julius Petri was refining his boss's idea: Koch had developed an earlier version in his private laboratory in 1881, and Petri made the final changes in 1887.

Which seaweed jelly did Fanny Hesse suggest for growing bacteria after using it in her kitchen for jams?

Agar stayed firm in summer heat that turned gelatin to liquid, which is why Hesse liked it for fruit jams and jellies. It had reached Europe through Dutch colonists in the East Indies.

Which Hungarian doctor cut deaths from childbed fever, a bacterial infection, by making colleagues wash their hands?

Ignaz Semmelweis saw maternal deaths at his Vienna clinic fall from 18% to under 2% once hands were washed in chlorinated lime. Offended doctors mocked him, and his ideas were rejected in his lifetime.

Which food-poisoning bacterium, able to grow at fridge temperatures, is named after a pioneer of antiseptic surgery?

Listeria honours Joseph Lister, and it is hardy enough to grow anywhere from 4 °C in a refrigerator up to body temperature. Deli meats, ready-to-eat salads and soft cheeses are common culprits.

The bacterial infection pertussis, whose violent fits can drag on for ten weeks or more, goes by which common name?

Whooping cough is named for the high-pitched gasp a patient makes when breathing in after a fit. Its other nickname is the 100-day cough, and a vaccine prevents it.

John Snow traced a deadly London cholera outbreak to contaminated water from a public pump on which Soho road?

Broad Street's pump was put out of action when parish authorities removed its handle on Snow's advice. The John Snow Society marks the moment with its annual Pumphandle Lectures.

The M in MRSA, a superbug strain of Staphylococcus aureus common in hospitals, stands for which antibiotic?

Methicillin is no longer even produced, but its name stuck. MRSA strains shrug off almost every beta-lactam drug, a family that includes the penicillins and cephalosporins.

Giant tube worms at deep-sea vents have no mouth or gut, relying on bacteria that draw energy from which gas?

Hydrogen sulfide gushing from the vents feeds bacteria housed in an organ called the trophosome. The worm's larvae start life with a mouth and gut, then lose them as adults.

Which machine, built like a pressure cooker, uses steam at about 121 °C to kill bacteria and their spores on lab tools?

Autoclave steam is held under pressure for 15 to 60 minutes, reaching a heat that open boiling cannot. Charles Chamberland invented the machine in 1879.

Pseudomonas syringae, a bacterium living on crop leaves, does much of its damage by causing what to form on them?

Frost forms at warmer temperatures than usual because proteins on the microbe's surface seed ice crystals. The same proteins are used to make artificial snow.

Griffith's famous mouse experiment showed harmless bacteria picking up a deadly trait from dead ones by which process?

Transformation is the uptake of loose DNA from the surroundings. Later experiments showed that the mysterious 'transforming principle' Frederick Griffith described in 1928 was the genetic material itself.

The Q in Q fever, a bacterial disease first described in Australian slaughterhouse workers, stands for which word?

Query was chosen because the cause was a mystery at the time. Rival names such as abattoir fever, or one using Queensland, were dropped to spare the cattle industry and the state bad publicity.

Agrobacterium tumefaciens, a bacterium used to slip new genes into crops, naturally causes which tumour-forming disease?

Crown gall tumours grow because the bacterium inserts a small segment of its own DNA into the host's genome. Genetic engineers replace that segment with the genes they want delivered.

Many antibiotics work by jamming bacterial ribosomes, which have which size on the Svedberg sedimentation scale?

70S ribosomes are built from a 30S and a 50S subunit: the figures do not add up because they measure how fast particles settle, not mass. Human ribosomes are 80S, so the drugs leave them alone.

Which discoverer of Prontosil, an early antibacterial drug, was forced by the Nazis to decline a Nobel Prize?

Gerhard Domagk was detained by the Gestapo for a week after the 1939 award was announced. He had already trusted the drug at home, using it to save his young daughter's arm from amputation.

Epulopiscium, a giant bacterium big enough to see with the naked eye, lives in the gut of which reef fish?

Surgeonfish that graze on algae host the microbe, first found in a specimen from the Red Sea in 1985. Its scientific name is Latin for 'a guest at a banquet of fish'.

In Richard Lenski's decades-long evolution experiment, one E. coli population famously learned to feed on what?

Citrate had been in the flasks all along, but E. coli normally cannot use it when oxygen is present. One of the twelve populations found a way after about 31,000 generations.

Swimming bacteria such as E. coli find food by alternating straight 'runs' with random changes of direction called what?

Tumbles happen when the flagella reverse and their rotating bundle flies apart, leaving the cell turning on the spot. When the food signal is improving, the bacterium simply tumbles less often.

Which German biologist, called a founder of bacteriology, first sorted bacteria into four groups according to shape?

Ferdinand Cohn's four groups were spheres, short rods, threads and spirals. He was also the first to show that some bacteria ride out harsh conditions by turning into tough dormant spores.

In Diamond v. Chakrabarty, the US Supreme Court ruled that an engineered oil-eating bacterium could be what?

Patented living things became possible with this 1980 ruling, which held that being alive is no bar to protection. Ananda Chakrabarty had built the microbe at General Electric to clean up oil spills.

The Gram stain, which sorts bacteria into two major classes, is named after a scientist from which country?

Denmark's Hans Christian Gram developed the method in 1884 while working in Berlin. The stain bears his surname, which is why Gram is written with a capital G.