Ikigai Daily
Menu
WonderMicrobiology fact

Bacteria can sense how many of their kind are nearby. Each cell releases signal molecules, and once enough have built up, the whole group switches certain behaviours on together. This is called quorum sensing.

American Society for Microbiology / NIH

ScienceNature

The story behind the card

The name borrows 'quorum', the minimum number of members a meeting needs before it can take decisions. It was first seen in 1970 in a glowing marine bacterium now called Aliivibrio fischeri, which lights up only when its population is dense, as inside the light organ of the Hawaiian bobtail squid; a single cell glowing alone would waste energy. The term itself was coined in 1994 by the microbiologists Claiborne Fuqua, Stephen Winans and Peter Greenberg. From 1998 to 2001, Bonnie Bassler showed that many kinds of bacteria use such signals, some even across species. Because disease-causing bacteria often wait for a quorum before attacking, researchers are testing drugs that block the signals instead of killing the bacteria.

Türkçe oku
Bakteriler, çevrelerinde kendi türlerinden kaç hücre bulunduğunu algılayabilir. Her hücre ortama sinyal molekülleri salar; bu moleküller yeterince birikince bütün grup belirli davranışları aynı anda başlatır. Buna çoğunluk algılama (quorum sensing) denir.

Adındaki “quorum” sözcüğü, bir toplantının karar alabilmesi için gereken en az üye sayısı, yani yeter sayı anlamına gelir. Olgu ilk kez 1970'te, bugün Aliivibrio fischeri adıyla bilinen, ışık saçan bir deniz bakterisinde gözlendi. Bu bakteri ancak kalabalıkken ışık verir; örneğin Hawaii'de yaşayan küçük bir mürekkep balığının ışık organının içinde. Tek başına ışıyan bir hücre enerjisini boşa harcamış olurdu. Terimi 1994'te mikrobiyologlar Claiborne Fuqua, Stephen Winans ve Peter Greenberg ortaya attı. Bonnie Bassler da 1998-2001 arasında pek çok bakteri türünün bu tür sinyaller kullandığını, bazılarının başka türlerle bile bu yolla haberleştiğini gösterdi. Hastalık yapan bakteriler saldırmak için çoğu zaman yeter sayıya ulaşmayı beklediğinden, araştırmacılar bakteriyi öldürmek yerine bu sinyalleri engelleyen ilaçlar üzerinde çalışıyor.

Sources and further reading

Background reading: Quorum sensing
Get the mobile appAbout our cards

Related cards

These cards share a subject or reading mode with the card above.

WonderScience

Some Great Basin bristlecone pines in the western United States are more than 4,800 years old, older than Egypt's Great Pyramid of Giza.

The oldest known living one, nicknamed Methuselah, grows in the White Mountains of eastern California; counting its growth rings shows it is more than 4,850 years old, and its exact location is kept secret to protect it. The Great Pyramid was built around 2560 BCE, a few centuries after Methuselah sprouted. Bristlecones grow extremely slowly on thin, dry dolomite soil, a rock similar to limestone, where few other plants survive, which spares them competition and fire. Their dense, resin-filled wood resists insects, fungi and rot, and dead trees can stand for thousands of years. In 1964 a researcher in Nevada cut down one tree, later called Prometheus, and counted at least 4,862 rings, making it the oldest tree then known.

Ikigai DailyRead card
WonderScience

Many fig trees can be pollinated only by tiny fig wasps, which crawl inside the closed fig to reach the hundreds of flowers hidden within.

A fig is not a single fruit but a closed cluster of flowers, lined inside with tiny blossoms. A female fig wasp, only one or two millimetres long, pushes in through a narrow opening at the tip, often losing her wings, then pollinates the flowers, lays her eggs and dies inside. Her young hatch and mate within the fig, and the new females leave carrying pollen to another tree. Most fig species rely on their own wasp species, a partnership thought to be tens of millions of years old. In western Turkey, around Aydın, growers still hang branches of wild male figs in their orchards so the wasps can pollinate the Smyrna-type figs grown for drying; this is called caprification. Many common garden figs ripen with no wasp at all.

USDA Forest Service / Royal SocietyRead card
StillnessScience

Seagrass meadows cover only about 0.1% of the seafloor, yet they account for roughly a tenth of the carbon buried in ocean sediments. Seagrasses are flowering plants that grow underwater along coasts.

Unlike seaweeds, which are algae, seagrasses have roots, leaves and flowers, and they grow in shallow coastal water on every continent except Antarctica. Their leaves slow the current so fine particles settle, and their roots bind the seabed. Dead leaves and roots are buried in mud with little oxygen, where they rot very slowly, so their carbon can stay locked away for centuries. Carbon stored by coastal plants in this way is called blue carbon. In the Mediterranean, including the Turkish coast, Posidonia oceanica meadows build thick mats of roots and sediment over thousands of years. Since the late nineteenth century, more than a fifth of the world's known seagrass area has been lost to dredging, pollution and coastal building.

NOAARead card
StillnessScience

Kelp forests grow in cool coastal seas from giant brown algae, not plants, and shelter a great variety of fish, invertebrates, seals and sea otters.

Kelp are large brown algae. Instead of roots they have a grip-like base called a holdfast, and gas-filled bulbs hold their fronds up towards the light. Giant kelp can grow up to about 60 centimetres a day and reach more than 30 metres, forming a canopy at the surface like the treetops of a forest. Kelp forests grow along cool coasts from California and Chile to South Africa, Australia and Norway. In the North Pacific, sea otters help protect them by eating sea urchins, which graze on kelp. Where otters were hunted out for their fur, urchins multiplied and stripped forests down to bare rock, leaving what are called urchin barrens.

NOAA Ocean ServiceRead card
WonderHistory

Amazonian dark earth, or terra preta, is an unusually fertile black soil made by people. Over generations, charcoal, broken pottery, bones and food waste built up around Indigenous settlements and turned thin rainforest soil rich.

Terra preta is Portuguese for 'black earth'. These soils formed between about 450 BCE and 950 CE at sites across the Amazon Basin, and in places the dark layer reaches one to two metres deep. Ordinary rainforest soil is poor, because heavy rain washes nutrients away, but charcoal barely breaks down and holds nutrients and water in place for centuries. Local farmers still use the soil today. It also changed how archaeologists see the Amazon: not as untouched wilderness, but as a landscape shaped by large, settled communities. Scientists now try to copy the method with 'biochar', charcoal made from farm waste and mixed into poor soils.

MIT / Amazonian dark earth researchRead card
Next card in the archiveMorse code spells each letter as a pattern of short and long signals, so a message can travel as clicks, tones, flashes of light or electrical pulses. From the 1840s it let the electric telegraph carry messages over long distances.Read next →