Since long before it gained fame as a precise gene-editing tool, CRISPR has had another job defending bacteria against viral invaders. And it’s far from alone. Ten sets of bacterial genes have similar, newly discovered defense roles, researchers report online January 25 in Science.

The discovery “probably more than doubles the number of immune systems known in bacteria,” says Joseph Bondy-Denomy, a microbiologist at the University of California, San Francisco, who wasn’t involved in the study.
Bacteria are vulnerable to deadly viruses called phages, which can hijack bacteria’s genetic machinery and force them to produce viral DNA instead. Some bacteria protect themselves against phage attacks with a system called CRISPR, which stores pieces of past invaders’ DNA so bacteria can recognize and fend off those phages in the future (SN: 4/15/17, p. 22). But only about 40 percent of bacteria have CRISPR, says study coauthor Rotem Sorek, a microbial genomicist at the Weizmann Institute of Science in Rehovot, Israel. That’s why he and his colleagues are hunting for other defense mechanisms.

Defense-related genes tend to cluster together in the genome, Sorek says. So his team sifted through genetic information from 45,000 microbes, flagging groups of genes with unknown functions that were located near known defense-related genes.

Many of the bacteria with these gene families hail from far-flung locations like the bottom of the ocean. So the researchers used the genomic data to synthesize the relevant bits of DNA and inserted them into Escherichia coli and Bacillus subtilis, which can both be grown and studied in the lab. Then, the researchers tracked how well the bacteria resisted phage attacks when various genes in a family were deleted. If getting rid of some of the genes affected the bacteria’s ability to fight off phages, that result suggested the group of genes was a defense system.

Nine groups of bacterial genes turned out to be antiphage defense systems, and one system protected against plasmids, another source of foreign DNA, the researchers found.
Previously discovered antiphage protective systems, such as CRISPR, have been described with acronyms, but, Sorek jokes, “we ran out of acronyms.” So the new systems are named after protective deities — like the Zorya, a pair of goddesses from Slavic mythology.

The data also reveal a possible shared origin between bacterial immune systems and similar defenses in more complex organisms, Sorek says. Some of the genes contained fragments of DNA that are also known to be an important part of the innate immune system in plants, mammals and invertebrates.

It’s likely the research will unleash a flurry of new studies to figure out how these new defense systems work and whether they, like CRISPR, might also be useful biotechnology tools, Bondy-Denomy predicts.

The physics behind a weird electrical phenomenon — glowing orbs of lightning — may be mimicked by something even stranger. A magnetic structure proposed for the natural oddity known as ball lightning makes an appearance in a newfound variety of a knotlike entity called a skyrmion, a team of scientists reports.

Typically observed during thunderstorms, ball lightning is poorly understood. Anecdotal reports describe eerily glowing spheres that float through the air for several seconds before fading (SN: 2/9/02, p. 87). That’s much longer than standard lightning strikes, which last tens of microseconds, and researchers are still struggling to explain how the fireballs persist.
One theory, proposed in the 1990s, suggests that ball lightning is a plasma held together by magnetic fields arranged in rings that link together into a knot. “Because it’s linked up in this tight way, it can’t really fall apart,” says physicist David Hall of Amherst College in Massachusetts. “That could provide a reason why ball lightning survives as long as it does.”
Now, Hall and colleagues have created an analog of such linked magnetic fields in a seemingly unrelated type of knotted structure, a skyrmion. Found in a variety of substances — from thin films of magnetic materials to liquid crystals — skyrmions are a kind of disturbance within matter
( SN: 2/17/18, p. 18 ). The objects can move like independent particles , shifting from place to place within a material while maintaining their knotted configuration ( SN: 10/18/14, p. 22 ). And like a tight knot in a thread, skyrmions are difficult to undo, making them relatively stable structures.
Hall and colleagues created their skyrmion in a state of matter called a Bose-Einstein condensate, composed of atoms cooled to a temperature so low that they all take on the same quantum state and begin acting as if they are one unified entity (SN: 10/13/01, p. 230). The atoms that make up the Bose-Einstein condensate each have a quantum property called spin, which makes them behave like tiny magnets.

When the scientists switched on a specially designed magnetic field, the spins arranged into a twisting structure of loops, knotting up into a configuration known as a Shankar skyrmion. That arrangement was predicted theoretically about 40 years ago, but not seen in the real world until now. While skyrmions found in thin magnetic materials are two-dimensional whirls, the new skyrmion is a 3-D beast, the researchers report March 2 in Science Advances.

Within the condensate, the spins produced something analogous to a magnetic field: The condensate behaved as if it were a charged particle being pushed around by a magnetic field when in reality no such magnetic field existed. Like the skyrmion itself, the scientists realized, the imitation magnetic field was knotted, and it matched the interlinked rings of magnetic fields proposed for ball lightning.

Eventually, studying 3-D knotted magnetic fields like those potentially present in ball lightning might help scientists devise better ways to control plasmas within future fusion reactors for generating power, the researchers suggest.

The creation of knotted structures in Bose-Einstein condensates is in its infancy, and such efforts are “very welcomed” says physicist Egor Babaev of KTH Royal Institute of Technology in Stockholm, who was not involved with the research. “People are just starting to scratch the surface of these objects.”

If signals from an alien civilization ever reach Earth, odds are the aliens will already be dead.

In an effort to update the 1961 Drake Equation, which estimates the number of detectable, intelligent civilizations in the Milky Way, physicist Claudio Grimaldi and colleagues calculated the area of the galaxy that should be filled with alien signals at a given time (SN Online: 11/1/09).

The team, which includes Frank Drake (now a professor emeritus at the SETI Institute in Mountain View, Calif., and the University of California, Santa Cruz), assumed technologically savvy civilizations are born and die at a constant rate. When a civilization dies out and stops broadcasting, the signals it had sent continue traveling like concentric ripples on a pond. Part of the Milky Way should be filled with these ghost signals.
If the civilization lasted less than 100,000 years — the time it takes light to cross the galaxy — then the odds of the signals reaching Earth while the civilization is still broadcasting are vanishingly small, the researchers report February 27 at arXiv.org. Humans, for example, have been transmitting radio waves for only about 80 years, so our radio waves cover less than 0.001 percent of the Milky Way.

“If the civilization emitted from the other side of the galaxy, when the signal arrives here, the civilization will already be gone,” says Grimaldi, of the Federal Polytechnical School of Lausanne in Switzerland.

Surprisingly, the team also calculated that the average number of E.T. signals crossing Earth at a given time should equal the number of civilizations currently transmitting — even if the civilizations we hear from aren’t the same ones presently broadcasting. Grimaldi is now working on a paper about what it means that we’ve found none so far.