Ikigai Daily
Menu
WonderFact

Bacteria do not only pass genes from parent to offspring: they can also hand them directly to other bacteria, even of different species. This is one of the main ways antibiotic resistance spreads.

Ikigai Daily

Science

The story behind the card

Biologists call this horizontal gene transfer. It happens in three main ways: bacteria can pass a plasmid, a small ring of DNA separate from their main chromosome, through direct contact (conjugation); they can pick up loose DNA left behind by dead cells (transformation); or viruses that infect bacteria can carry genes from one cell to the next (transduction). Its medical importance became clear in Japan, where a 1959 publication showed that resistance to several antibiotics could jump between different species of gut bacteria. A recent example is mcr-1, a gene that makes bacteria resistant to colistin, one of the last-resort antibiotics. It was reported in 2015 on a plasmid in bacteria from pigs in China and was soon found in many countries. This is why resistance can move through a hospital or farm far faster than inheritance alone would allow.

Türkçe oku
Bakteriler genlerini yalnızca bölünerek oluşan yeni hücrelere aktarmaz; başka bakterilere, hatta farklı türlerden bakterilere de doğrudan verebilir. Antibiyotik direncinin başlıca yayılma yollarından biri budur.

Biyologlar buna yatay gen aktarımı der. Bunun üç temel yolu vardır. Bakteriler, ana kromozomlarından ayrı duran küçük DNA halkalarını, yani plazmitleri doğrudan temasla birbirine geçirebilir (konjugasyon). Ölen hücrelerden ortada kalan DNA'yı içlerine alabilirler (transformasyon). Bakterileri enfekte eden virüsler de bir hücreden ötekine gen taşıyabilir (transdüksiyon). Konunun tıptaki önemi Japonya'da anlaşıldı: 1959'da yayımlanan bir çalışma, birkaç antibiyotiğe karşı direncin farklı bağırsak bakterisi türleri arasında geçebildiğini gösterdi. Daha yeni bir örnek mcr-1 genidir: Bu gen bakterileri, son çare olarak kullanılan antibiyotiklerden kolistine karşı dirençli kılar. 2015'te Çin'de domuzlardan alınan bakterilerde, bir plazmit üzerinde bildirildi ve kısa sürede birçok ülkede bulundu. Bu yüzden direnç bir hastanede ya da çiftlikte, yalnızca kalıtımla mümkün olabileceğinden çok daha hızlı yayılabilir.

Sources and further reading

Background reading: Horizontal gene transfer
Get the mobile appAbout our cards

Related cards

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

WonderHistory

The Industrial Revolution put the clock in charge of the working day. Before factories, most people worked by daylight, the seasons and the task in hand; from the 1770s, mills such as Richard Arkwright's at Cromford in Derbyshire ran day and night in twelve-hour shifts.

The historian E. P. Thompson traced this change in a famous essay of 1967, “Time, Work-Discipline, and Industrial Capitalism”. Farm and craft work, he argued, had been measured by tasks: milking, harvesting, finishing a piece. Factory work was measured in hours. Cromford Mill, opened in 1771, was the world's first water-powered cotton-spinning mill. It started with about 200 workers, most of them women and children, the youngest only seven. Bells rang at 5 in the morning and 5 in the evening, the gates were shut at exactly 6, and anyone late lost that day's pay and was fined another. In industrial towns, where alarm clocks were not yet cheap or reliable, “knocker-ups” were paid a few pence a week to tap on upstairs windows with long poles.

Ikigai DailyRead card
WonderHistory

Less than 66 years, well within a single lifetime, separate the first powered aeroplane flight from the first Moon landing. Orville Wright flew for 12 seconds and 37 metres on 17 December 1903; Apollo 11 landed on the Moon on 20 July 1969.

The Wright brothers, bicycle makers from Dayton, Ohio, flew near Kitty Hawk, North Carolina, and that first hop was shorter than the wingspan of a Boeing 747. What followed came fast. In 1919 John Alcock and Arthur Brown flew non-stop across the Atlantic; in 1927 Charles Lindbergh did it alone, from New York to Paris; and in 1947 Chuck Yeager flew faster than sound. Orville Wright died in 1948, nine years before the Soviet satellite Sputnik opened the space age. Yuri Gagarin orbited the Earth in 1961, and in July 1969 Neil Armstrong took a scrap of the 1903 Flyer's wood and fabric with him to the Moon.

Ikigai DailyRead card
WonderHistory

The Cold War between the United States and the Soviet Union (1947–1991) was fought mostly without direct battles between the two. They competed instead through weapons, science, sport, films, propaganda and the race into space.

George Orwell used the phrase “cold war” in 1945, and the American journalist Walter Lippmann made it popular in 1947. Because nuclear weapons made open war between the superpowers too dangerous, the rivalry spread into other arenas. After the Soviet Union launched the Sputnik satellite in 1957, the United States passed the National Defense Education Act of 1958 to fund science, maths and language teaching. In 1959, at an American exhibition in Moscow, Vice-President Richard Nixon and the Soviet leader Nikita Khrushchev argued about capitalism and communism in a model kitchen, an exchange remembered as the Kitchen Debate. In 1972 in Reykjavík, the American Bobby Fischer beat the Soviet champion Boris Spassky for the world chess title. The Olympics were boycotted in turn: the United States and many allies stayed away from Moscow in 1980, and most of the Soviet bloc from Los Angeles in 1984.

Ikigai DailyRead card
WonderHistory

The Apollo Guidance Computer, which helped steer astronauts to the Moon, was one of the first computers built from integrated circuits: small silicon chips that each carry several electronic components. Until 1965, Apollo was the biggest user of these new chips.

The computer was designed at the MIT Instrumentation Laboratory from 1962 and built by Raytheon, and one flew in every Apollo command module and lunar module. The chip was still a new invention: Jack Kilby and Robert Noyce had made the first ones in 1958 and 1959. MIT used almost a single type throughout, a simple logic circuit designed by Fairchild Semiconductor, repeated thousands of times. According to the Computer History Museum, Apollo bought some 200,000 of them at 20 to 30 dollars each, and by 1965 the Minuteman missile programme had become the bigger buyer. Orders like these kept the young industry going until prices fell: the average chip cost 50 dollars in 1962 and 2.33 dollars in 1968. The Space Race is often credited with GPS too, but GPS was a separate US Department of Defense project, begun in 1973.

Ikigai DailyRead card
WonderHistory

On 12 April 1961 the Soviet cosmonaut Yuri Gagarin, aged 27, became the first human in space. His Vostok 1 spacecraft circled the Earth once, and the flight lasted 108 minutes from launch to landing.

Gagarin, who had trained as a foundry worker before becoming an air force pilot, was launched from Baikonur, in today's Kazakhstan. As the rocket lifted off he called out “Poyekhali!” (“Let's go!”). His orbit took him as high as 327 kilometres. On the way back he ejected from the capsule about 7 kilometres above the ground and came down by his own parachute near Engels, in the Saratov region, where a farm worker and her granddaughter were the first to meet him. Because the record rules of the day required pilots to land inside their craft, the Soviet Union claimed he had, and admitted the truth only in 1971. Gagarin became famous around the world. He died in a training-jet crash in 1968, aged 34. Since 2011 the United Nations has marked 12 April as the International Day of Human Space Flight.

Ikigai DailyRead card
Next card in the archiveAntibiotics kill bacteria or stop them multiplying by attacking parts that viruses do not have, such as the bacterial cell wall. Colds and flu are caused by viruses, so antibiotics cannot treat them.Read next →