Ultrasound can now track bacteria in the body like sonar detects submarines.

For the first time, researchers have genetically modified microbes to form gas-filled pouches that scatter sound waves to produce ultrasound signals. When these bacteria are placed inside an animal, an ultrasound detector can pick up those signals and reveal the microbes’ location, much like sonar waves bouncing off ships at sea, explains study coauthor Mikhail Shapiro, a chemical engineer at Caltech.

This technique, described in the Jan. 4 Nature, could help researchers more closely monitor microbes used to seek and destroy tumors or treat gut diseases (SN: 11/1/14, p. 18).
Repurposing ultrasound, a common tissue-imaging method, to map microbes creates “a tool that nobody thought was even conceivable,” says Olivier Couture, a medical biophysicist at the French National Center for Scientific Research in Paris, who wasn’t involved in the work.

Until now, researchers have tracked disease-fighting bacteria in the body by genetically engineering them to glow green in ultraviolet images. But that light provides only blurry views of microbes in deeper tissue — if it can be seen at all. With ultrasound, “we can go centimeters deep and still see things with a spatial precision on the order of a hundred micrometers,” Shapiro says.

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Shapiro and his colleagues engineered a strain of E. coli used to treat gut infection to form gas compartments, and injected these bacteria into mice’s bellies. Unlike glowing bacteria — which could only be pinpointed to somewhere in a mouse’s abdomen — ultrasound images located the gas-filled microbes in the colon. The researchers also used their ultrasound technique in mice to image Salmonella bacteria, which could be used to deliver cancer-killing drugs to tumor cells.

Bacteria that produce ultrasound signals can also be designed to help diagnose illnesses, Shapiro says. For instance, a patient could swallow bacteria engineered to create gas pockets wherever the microbes sense inflammation. A doctor could then use ultrasound to search for inflamed tissue, rather than performing a more invasive procedure like a colonoscopy.

Newly described little scaly bits could push back the fossil record of the moth-and-butterfly branch on the tree of life by some 70 million years. That raises the question of whether the drinking-straw mouthparts evolved long before the flower nectar many drink today.

The microscopic ridged scales date from roughly 200 million years ago, around the time of one of Earth’s less famous mass extinctions, says fossil-pollen specialist Bas van de Schootbrugge of Utrecht University in the Netherlands. During an unrelated study of ocean oxygen during this dire time, he and his colleagues pulled up cores of sediment in northern Germany near Braunschweig from what had once been a huge lagoon. In the sediment lay mere dots of insect scales.
Comparing the ridges and inner structure of the scales with those from modern insects suggests the fossils came from the evolutionary branch of insects that today gives us moths and butterflies with nectar-sipping mouthparts. No recognizable mouthparts appeared in the sediment. Yet the early existence of distinctive scales might mean this moth-butterfly drinking organ, a proboscis, evolved before the explosion of the classic flowering plants that offer nectar for pollination, van de Schootbrugge and colleagues propose January 10 in Science Advances.
The land already had plants: ferns, mosses and their relatives growing under trees that formed just-about naked seeds, without cushy protective ovaries and other floral coddling. Naked-seeded plants, many of them wind-pollinated such as pines and other conifers, thrive today. But the great evolutionary burst of true flowers—magnolias, roses, legumes, asters and the whole multicolored rainbow — that many moths and butterflies pollinate had yet to arise.These fossils date from a turbulent time when the great land mass called Pangea was cracking into continents. As the Triassic Period ended and the Jurassic dawned, volcanic eruptions on the straining land spewed greenhouse gases and toxins that changed the atmosphere and climate.
The previous record-holder for earliest moth-butterfly fossils came from about 130 million years ago, a bit after a major expansion of flowering plants. But when coauthor Timo van Eldijk, also at Utrecht, compared the newly found insect scales with those from silverfish, beetles and other scaly insects, modern scales of a big branch of the moth-butterfly lineage proved the best match.
In the times of the ancient scales, generally hot and dry conditions might have favored mouthparts specialized for drinking whatever liquids were to be found, the researchers propose.

Other work on how this proboscis evolved proposes that early moths started with chewing mouthparts and ate spores and pollen, says Harald W. Krenn of the University of Vienna. He and colleagues have proposed an intermediate phase of a short, tubelike structure good for slurping up droplets such as “honeydew” copiously excreted by sap-feeding aphids. A big question, though, is when early moths might have evolved such a drinking convenience.

The notion that the moth mouthparts arose before a big floral takeover sounds plausible to paleoecologist Conrad Labandeira of the Smithsonian Institution in Washington, D.C. Drinking-straw mouthparts had evolved in at least three other big insect groups (dipteran flies, lacewings and scorpionflies) somewhat before the full floral evolutionary extravaganza. Even some of the ancient naked-seeded plant groups, such as cycads, secrete nutritious droplets from reproductive structures that modern insects visit.

Interpreting the scales as a sign of an early moth proboscis is “possible,” says taxonomist Erik van Nieukerken of the Naturalis Biodiversity Center in Leiden, the Netherlands, whose specialties include early moths. There are other possibilities, too, for imagining ancient moth mouthparts, he cautions. Saying definitely that the newfound scales reveal the dawn of the proboscis might be “a bit too quick.”

A pair of ancient Egyptian mummies, known for more than a century as the Two Brothers, were actually half brothers, a new study of their DNA finds.

These two, high-ranking men shared a mother, but had different fathers, say archaeogeneticist Konstantina Drosou of the University of Manchester in England and her colleagues. That muted family tie came to light thanks to the successful retrieval of two types of DNA from the mummies’ teeth, the scientists report in the February Journal of Archaeological Science: Reports. The finding highlights the importance ancient Egyptians placed on maternal lines of descent, Drosou’s group contends.
Questions have swirled about the biological backgrounds of the mummified men ever since they were found together in a tomb near the village of Rifeh in 1907. The tomb dates to ancient Egypt’s 12th Dynasty, between 1985 B.C. and 1773 B.C. Coffin inscriptions mention a female, Khnum-Aa, as the mother of both men. And both mummies are described as sons of an unnamed local governor. It has always been unclear if those inscriptions refer to the same man, but discoverers decided the mummies were full brothers, because the two were buried next to each other and had the same mother.

Over time, differences discovered in the men’s skull shapes and other skeletal features raised suspicions that the Two Brothers were not biologically related at all. And some researchers argued that the inscriptions indicating the men had the same mother were misleading.

Adding to those doubts, a 2014 paper reported differences between the two mummies’ mitochondrial DNA, suggesting one or both had no biological link to Khnum-Aa. Mitochondrial DNA typically gets inherited from the mother.

But that study extracted ancient DNA from liver and intestinal samples using a method susceptible to contamination with modern human and bacterial DNA, Drosou’s team argues. In the new work, researchers isolated and assembled short pieces of mitochondrial and Y-chromosome DNA from both mummies’ teeth using the latest methods. The Y chromosome determines male sex and gets passed from father to son. This approach minimizes potential contamination from modern sources (SN Online: 5/31/17).
That new DNA evidence “proves the hieroglyphic text [on the mummies’ coffins] to be accurate,” at least in saying the mummified men had the same mother, says Egyptologist and study coauthor Campbell Price, curator of the Egypt and Sudan collections at the Manchester Museum in England.

Unlike the deference given to Khnum-Aa as a named parent of both interred individuals, he says, the coffin inscriptions must refer to different fathers who were considered peripheral family members and thus left unnamed. “Power may have been transferred down the female line rather than simply by a son inheriting [high rank] from his father,” Price suggests. Khnum-Aa’s background, social standing and genetic makeup, however, remain a mystery.

Genetic evidence that two half brothers were buried in the same tomb and placed in coffins that name only their mother makes sense, says Egyptologist Joann Fletcher at the University of York in England. Many written sources from ancient Egypt show precedence to the maternal line, “from the official lists of Egypt’s early kings whose names are accompanied by those of their mothers to nonroyal individuals, who likewise cite only their mother’s name,” Fletcher explains.

Dates of death on the mummies’ linen wrappings suggest that Khnum-Nakht died first, at around age 40, Price says. A few months later, Nakht-Ankh died at about age 60. The causes of their deaths are unknown.

Unless you are a recent arrival from another universe, you’ve no doubt heard that this one is expanding. It’s getting bigger all the time. What’s more, its growth rate is accelerating. Every day, the universe expands a little bit faster than it did the day before.

Those day-to-day differences are negligible, though, for astronomers trying to measure the universe’s expansion rate. They want to know how fast it is expanding “today,” meaning the current epoch of cosmic history. That rate is important for understanding how the universe works, knowing what its ultimate fate will be and even what it is made of. After all, the prime mission of the Hubble Space Telescope when it was launched in 1990 was to help determine that expansion rate (known, not coincidentally, as the Hubble constant, named for the astronomer Edwin Hubble).
Since then evidence from Hubble (the telescope) and other research projects has established a reasonably precise answer for the Hubble constant: 73, in the units commonly used for this purpose. (It means that two independent astronomical bodies separated by 3.26 million light-years will appear to be moving away from each other at 73 kilometers per second.) Sure, there’s a margin of error, but not much. The latest analysis from one team, led by Nobel laureate Adam Riess, puts the Hubble constant in the range of 72–75, as reported in a paper posted online January 3. Considering that as late as the 1980s astronomers argued about whether the Hubble constant was closer to 40 or 90, that’s quite an improvement in precision.

But there’s a snag in this success. Current knowledge of the universe suggests a way to predict what the Hubble constant ought to be. And that prediction gives a probable range of only 66–68. The two methods don’t match.

“This is very surprising, I think, and very interesting,” Riess, of the Space Telescope Science Institute in Baltimore, said in a talk January 9 at a meeting of the American Astronomical Society.

It’s surprising because astrophysicists and cosmologists thought they had pretty much figured the universe out. It’s made up of a little bit of ordinary matter, a lot of some exotic “dark matter” of unknown identity, and even more of a mysterious energy permeating the vacuum of space, exerting gravitational repulsion. Remember that acceleration of the expansion rate? It implies the existence of such energy. Because nobody knows what it is, people call it “dark energy,” while suspecting that its real name is lambda, the Greek letter that stands for “cosmological constant.” (It’s called a constant because any part of space should possess the same amount of vacuum energy.) Dark energy contributes something like 70 percent of the total mass-energy content of the universe, various lines of evidence indicate.
If all that’s right, then it’s not all that hard to infer how fast the universe should be expanding today. You just take the recipe of matter, dark matter and dark energy and add some ghostly subatomic particles known as neutrinos. Then you carefully measure the temperature of deep space, where the only heat is the faint glow remaining from the Big Bang. That glow, the cosmic microwave background radiation, varies slightly in temperature from point to point. From the size of those variations, you can calculate how far the radiation from the Big Bang has been traveling to reach our telescopes. Combine that with the universe’s mass-energy recipe, and you can calculate how fast the universe is expanding. (You can, in fact, do this calculation at home with the proper mathematical utensils.)

An international team’s project using cosmic microwave background data inferred a Hubble constant of 67, substantially less than the 73 or 74 based on actually measuring the expansion (by analyzing how the light from distant supernova explosions has dimmed over time).

When this discrepancy first showed up a few years ago, many experts believed it was just a mirage that would fade with more precise measurement. But it hasn’t.

“This starts to get pretty serious,” Riess said at the astronomy meeting. “In both cases these are very mature measurements. This is not the first time around for either of these projects.”

One commonly proposed explanation contends that the supernova studies are measuring the local value of the Hubble constant. Perhaps we live in a bubble, with much less matter than average, skewing expansion measurements. In that case, the cosmic microwave background data might provide a better picture of the “global” expansion rate for the whole universe. But supernovas observed by the Hubble telescope extend far enough out to refute that possibility, Riess said.

“Even if you thought we lived in a void…, you still are basically stuck with the same problem.”

Consequently it seems most likely that something is wrong with the matter-energy recipe for the universe (technically, the cosmological standard model) used in making the expansion rate prediction. Maybe the vacuum energy driving cosmic acceleration is not a cosmological constant after all, but some other sort of field filling space. Such a field could vary in strength over time and throw off the calculations based on a constant vacuum energy. But Riess pointed out that the evidence is growing stronger and stronger that the vacuum energy is just the cosmological constant. “I would say there we have less and less wiggle room.”

Another possibility, appealing to many theorists, is the existence of a new particle, perhaps a fourth neutrino or some other relativistic (moving very rapidly) particle zipping around in the early universe.

“Relativistic particles — theorists have no trouble inventing new ones, ones that don’t violate anything else,” Riess said. “Many of them are quite giddy about the prospect of some evidence for that. So that would not be a long reach.”

Other assumptions built into the current cosmological standard model might also need to be revised. Dark matter, for example, is presumed to be very aloof from other forms of matter and energy. But if it interacted with radiation in the early universe, it could have an effect similar to that of relativistic particles, changing how the energy in the early universe is divided up among its components. Such a change in energy balance would alter how much the universe expands at early times, corrupting the calibrations needed to infer the current expansion rate.

It’s not the first time that determining the Hubble constant has provoked controversy. Edwin Hubble himself initially (in the 1930s) vastly overestimated the expansion rate. Using his rate, calculations indicated that the universe was much younger than the Earth, an obvious contradiction. Even by the 1990s, some Hubble constant estimates suggested an age for the universe of under 10 billion years, whereas many stars appeared to be several billion years older than that.

Hubble’s original error could be traced to lack of astronomical knowledge. His early overestimates turned out to be signals of a previously unknown distinction between different generations of stars, some younger and some older, Riess pointed out. That threw off distance estimates to some stars that Hubble used to estimate the expansion rate. Similarly, in the 1990s the expansion rate implied too young a universe because dark energy was not then known to exist and therefore was not taken into account when calculating the universe’s age.

So the current discrepancy, Riess suggested, might also be a signal of some astronomical unknown, whether a new particle, new interactions of matter and radiation, or a phenomenon even more surprising — something that would really astound a visitor from another universe.