60 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.