BOSTON — Moms get blamed for a lot — including their kids’ cavities. But new data show that the most common cause of tooth decay, the bacterium Streptococcus mutans, doesn’t always come from mother-to-child transmission.

Researchers from the University of Alabama at Birmingham studied 119 children in rural Alabama and 414 of their household contacts, tracking the path of S. mutans. Contrary to expectation, 40 percent of the children did not share any strains with their mothers. Instead, those strains usually overlapped with those of siblings and cousins. And 72 percent of children carried a strain of S. mutans that no one else in the family had, probably picked up from other children at school, day care or other locations. The research was presented June 17 at ASM Microbe 2016, a meeting of the American Society for Microbiology and the Interscience Conference on Antimicrobial Agents and Chemotherapy.

While maternal transmission was still the most common route, “we’re not trying to say ‘Don’t kiss your babies,’” said Stephanie Momeni, a doctoral candidate at UAB. Rather, the ultimate goal of the research is to learn whether particular strains of S. mutans pose a greater hazard for dental health. Knowing that would help identify children who might be in need of more aggressive dental hygiene.

Driverless cars are revved up to make getting from one place to another safer and less stressful. But clashing views over how such vehicles should be programmed to deal with emergencies may stall the transportation transformation, a new study finds.

People generally approve of the idea of automated vehicles designed to swerve into walls or otherwise sacrifice their passengers to save a greater number pedestrians, say psychologist Jean-François Bonnefon of the Toulouse School of Economics in France and his colleagues. But here’s the hitch: Those same people want to ride in cars that protect passengers at all costs, even if pedestrians end up dying, the researchers report in the June 24 Science.
“Autonomous cars can revolutionize transportation,” says cognitive scientist and study coauthor Iyad Rahwan of the University of California, Irvine and MIT. “But they pose a social and moral dilemma that may delay adoption of this technology.”

Such conflict puts makers of computerized cars in a tough spot, Bonnefon’s group warns. Given a choice between driverless cars programmed for the greater good or for self-protection, consumers will overwhelmingly choose the latter. Regulations to enforce the design of passenger-sacrificing cars would backfire, the scientists suspect, driving away potential buyers. If so, plans for easing traffic congestion, reducing pollution and eliminating many traffic accidents with driverless cars would be dashed.
Further complicating matters, the investigators say, automated vehicles will need to respond to emergency situations in which an action’s consequences can’t be known for sure. Is it acceptable, for instance, to program a car to avoid a motorcycle by swerving into a wall, since the car’s passenger is more likely to survive a crash than the motorcyclist?

“Before we can put our values into machines, we have to figure out how to make our values clear and consistent,” writes Harvard University philosopher and cognitive scientist Joshua Greene in the same issue of Science.
But moral dilemmas have long dogged human civilizations and are sometimes unavoidable, says psychologist Kurt Gray of the University of North Carolina in Chapel Hill. People may endorse conflicting values depending on the situation — say, saving others when taking an impersonal perspective and saving oneself when one’s life is on the line.

Workable compromises can be reached, Gray says. If all driverless cars are programmed to protect passengers in emergencies, automobile accidents will still decline, he predicts. Despite being a danger to pedestrians on rare occasions, those vehicles “won’t speed, won’t drive drunk and won’t text while driving, which would be a win for society.”

Bonnefon’s team examined attitudes toward driverless vehicles in six online surveys conducted between June and November 2015. A total of 1,928 U.S. participants completed surveys.

Participants generally disapproved of automated vehicles sacrificing a passenger to save one pedestrian, but approval rose sharply with the number of pedestrians’ lives that could be saved. For instance, about three-quarters of volunteers in one survey said it was more moral for an automated car to sacrifice one passenger rather than kill 10 pedestrians. That trend held even when volunteers imagined they were in a driverless car with family members.

Bonnefon doubts those participants were simply trying to impress researchers with “noble” answers. But opinions changed when participants were asked about their views of driverless cars in actual practice. Responders to another survey similarly rated pedestrian-protecting automated cars as more moral, but most of those same people readily admitted that they wanted passenger-protecting cars for themselves. Other participants considered driverless cars that swerved to avoid pedestrians as good for others to drive but had little intention to buy one.

Volunteers expressed weak support for a law forcing either human drivers or automated cars to swerve to avoid pedestrians. Even in a hypothetical case where a passenger-sacrificing automated car saved the lives of 10 pedestrians, participants rated their willingness to have such sacrifices legally enforced at only 40 on a scale of 0 to 100. A final survey found that participants were much less likely to consider buying driverless cars subject to pedestrian-protecting regulations after being presented with situations in which they were riding alone, with an unspecified family member or with their child.

NEW ORLEANS — In a primordial soup on ancient Earth, droplets of chemicals may have paved the way for the first cells. Shape-shifting droplets split, grow and split again in new computer simulations. The result indicates that simple chemical blobs can exhibit replication, one of the most basic properties of life, physicist Rabea Seyboldt of the Max Planck Institute for the Physics of Complex Systems in Dresden, Germany, reported March 16 at a meeting of the American Physical Society.

Within a liquid, small droplets of particular chemicals can separate out, like beads of oil in water. Such globules typically remain spherical, growing as they merge with other drops. But in simulations, Seyboldt and colleagues found that droplets might behave in a counterintuitive way under certain conditions, elongating and eventually dividing into two.
If additional droplet material is continuously produced in reactions in the primordial soup, chemicals will accumulate on either end of a droplet, causing it to elongate, the simulations show. Meanwhile, waste products from the droplet are eliminated from the middle, causing the droplet to pinch in and eventually split. The resulting pair of droplets would then grow and split again to create a new generation. In addition to the above reactions, the process requires an energy source, such as heat or chemicals from a hydrothermal vent, to get reactions going.

The study, which was also described in Nature Physics in December, is theoretical — the researchers didn’t select particular chemicals for study but simply showed that certain types of reactions could cause droplets to split.

How such droplets would have evolved into vastly more complicated cells is unknown. “This is really a minimal scenario that’s supposed to give the very first indications of something that goes towards life, but if you look at living cells today, they’re infinitely more complex,” Seyboldt said.

PHILADELPHIA — Protein-manufacturing factories within cells are picky about which widgets they construct, new research suggests. These ribosomes may not build all kinds of proteins, instead opting to craft only specialty products.

Some of that specialization may influence the course of embryo development, developmental biologist and geneticist Maria Barna of Stanford University School of Medicine and colleagues discovered. Barna reported the findings December 5 at the joint meeting of the American Society for Cell Biology and European Molecular Biology Organization.
Ribosomes, which are themselves made up of many proteins and RNAs, read genetic instructions copied from DNA into messenger RNAs. The ribosomes then translate those instructions into other proteins that build cells and carry out cellular functions. A typical mammalian cell may carry 10 million ribosomes. “The textbook view of ribosomes is that they are all the same,” Barna said. Even many cell biologists have paid little attention to the structures, viewing them as “backstage players in controlling the genetic code.”

But that view may soon change. Ribosomes actually come in many varieties, incorporating different proteins, Barna and colleagues found. Each variety of ribosome may be responsible for reading a subset of messenger RNAs, recent studies suggest. For instance, ribosomes containing the ribosomal protein RPS25 build all of the proteins involved in processing vitamin B12, Barna and colleagues reported July 6 in Molecular Cell. Vitamin B12 helps red blood cells and nerves work properly, among other functions. Perhaps other biological processes are also controlled, in part, by having specific types of ribosomes build particular proteins, Barna said.

In unpublished work presented at the meeting, Barna and colleagues also found that certain ribosome varieties may be important at different stages of embryonic development. The researchers coaxed embryonic stem cells growing in lab dishes to develop into many types of cells. The team then examined the ribosomal proteins found in each type of cell. Of the 80 ribosomal proteins examined, 31 changed protein levels in at least one cell type, Barna said. The finding may indicate that specialized ribosomes help set a cell’s identity.

Although Barna’s idea of diverse ribosomes goes against the classical textbook view, “the concept is not heretical at all,” says Vassie Ware, a molecular cell biologist at Lehigh University in Bethlehem, Pa., not involved in the work.
These findings may help explain why some people with mutations in certain ribosomal protein genes develop conditions such as Diamond-Blackfan anemia — a blood disorder in which the bone marrow doesn’t make enough red blood cells — but don’t have problems in other body tissues, Ware says.

That disease is caused by mutations in the RPL5 and RPL11 genes, which encode ribosomal building blocks. If all ribosomes were alike, people with mutations in ribosomal components should have malfunctions all over their bodies, or might not ever be born. RPL5 and RPL11 proteins may be part of specialized ribosomes that are important in the bone marrow but not elsewhere in the body.

LOS ANGELES — Quantum computers are bulking up.

Researchers from Google are testing a quantum computer with 72 quantum bits, or qubits, scientists reported March 5 at a meeting of the American Physical Society — a big step up from the company’s previous nine-qubit chip.

The team hopes to use the larger quantum chip to demonstrate quantum supremacy for the first time, performing a calculation that is impossible with traditional computers (SN: 7/8/17, p. 28), Google physicist Julian Kelly reported.
Achieving quantum supremacy requires a computer of more than 50 qubits, but scientists are still struggling to control so many finicky quantum entities at once. Unlike standard bits that take on a value of 0 or 1, a qubit can be 0, 1 or a mashup of the two, thanks to a quantum quirk known as superposition.

Nicknamed Bristlecone because its qubits are arranged in a pattern resembling a pinecone’s scales, the computer is now being put through its paces. “We’re just starting testing,” says physicist John Martinis of Google and the University of California, Santa Barbara. “From what we know so far, we’re very optimistic.” The quantum supremacy demonstration could come within a few months if everything works well, Martinis says.

Google is one of several companies working to make quantum computers a reality. IBM announced it was testing a 50-qubit quantum computer in November 2017 (SN Online: 11/10/17), and Intel announced a 49-qubit test chip in January.

And the winner is in. Of the roughly 34,000 submissions sent in by the public, NASA has finally chosen an official nickname for the New Horizons spacecraft’s next destination: Ultima Thule.

New Horizons is scheduled to visit the tiny Kuiper Belt object on New Year’s Day 2019. NASA announced in November that it was seeking public input for a catchier name than the object’s existing moniker: 2014 MU69. Submissions varied wildly, ranging from the mythological Olympus to the much less grandiose Nubbin, defined as a “small lump or residual part” (SN Online: 11/7/17).

The final choice, Ultima Thule (pronounced “thoo-lee”), was announced March 13. It means “beyond the borders of the known world.” The nickname is a nice fit since the object will be the most distant solar system body ever visited.

After the flyby, NASA will submit a formal name to the International Astronomical Union based on whether Ultima Thule is a single object, a binary pair or a multi-object system.