Daily briefing: Largest bacterium ever discovered is 2 cm long

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Dinosaurs met their end in spring

Palaeontologists have unearthed fossilized fish that suggest the asteroid that killed off the dinosaurs struck in spring. The fossils come from Tanis, a remarkable site in North Dakota, which some scientists think captured what happened just hours after the asteroid crashed. But some are yet to be convinced by this explanation because detailed descriptions of the site’s geology aren’t available, and relatively few scientists have visited it.

Briefing readers might remember Tanis from 2019, when its extraordinary geology was controversially first reported in The New Yorker.

Nature | 5 min read

Reference: Nature paper & Scientific Reports paper

Three shots might hit ‘ceiling of immunity’

A fourth booster of a COVID-19 vaccine seems to restore antibodies to levels observed after the third dose, but provides only a modest boost in protection. A small trial carried out in Israel, which has not yet been peer reviewed, suggests that current mRNA vaccines hit a ‘ceiling of immunity’ after the third dose. However, observational studies from Israel have shown higher levels of protection against infection and severe disease from a fourth shot, which could be crucial for people at high risk.

Nature | 4 min read

Reference: medRxiv preprint 1 & medRxiv preprint 2

Largest bacterium ever discovered

A newly discovered bacterium, Thiomargarita magnifica, challenges the definition of a microbe: its filament-like single cell is up to 2 centimetres long. T. magnifica achieves its unprecedented size by having unique cellular features: two membrane sacs. One is filled with its genetic material; the other, which is much larger, helps to keep its cellular contents pressed up against its outer cell wall so that the molecules it needs can diffuse in and out. Researchers have dubbed these sacs ‘pepins’ — inspired by the pips in fruit — and note that they blur the line between single-celled prokaryotes and eukaryotes (the group that includes humans), which pack their DNA into a nucleus.

Science | 6 min read

Reference: bioRxiv preprint (not peer reviewed)

Nations gather for plastic-pollution treaty

Almost 200 countries will convene next week to draw up a blueprint for the first-ever global agreement on plastic pollution. Negotiators will attend the United Nations Environment Assembly (UNEA), in person and remotely, in Kenya. They will aim to set the groundwork for a final deal, which will be hammered out in detail over the following years. A draft resolution, modelled on the United Nations’s climate treaty, suggests a legally binding commitment to address the full lifecycle of plastics.

Science | 5 min read

Reference: Draft resolution

Features & opinion

Female scientists are changing Africa

A series of Nature interviews with female African scientists and a poll of 249 African researchers show that many women working in research in African countries are thriving. But they still need policies that help to lower the barriers to their success. Our series also illustrates the impacts of chronic funding shortages in Africa. Researchers outside the continent have an important part to play by collaborating with those who live there and sharing knowledge, experience and funding.

Nature | 5 min read

Smash barriers for physician-scientists

Gender equity in medicine has been elusive, and the challenges of the pandemic have made the situation even worse, argue eight physician-scientists. “While similar numbers of men & women enroll in MD/PhD programs… only 27% of women (vs 73% of men) plan to continue significant research,” writes co-author Joy Wu in an accompanying Twitter thread detailing the evidence of the barriers to advancement. They outline a framework for retaining female physicians in research, with a particular focus on the unequal burden of childcare.

Nature Medicine | 8 min read & accompanying Twitter thread

The mystery of the false teeth

Paul Bishop, a civil servant from Greater Manchester, received a package one day with a complete top set of his own false teeth, which he had last seen on a boozy holiday to Spain, when he vomited them into a bin. The package came with a letter stating that the teeth had been found by waste collectors, who sent them to one of Spain’s largest public research bodies, where they were eventually swabbed for DNA that was matched to Bishop. The story went viral, but a closer examination reveals the truth might not be what it seems.

Wired | 12 min read