Wiping out gut bacteria impairs brain

Obliterating bacteria in the gut may hurt the brain, too.

In mice, a long course of antibiotics that wiped out gut bacteria slowed the birth of new brain cells and impaired memory, scientists write May 19 in Cell Reports. The results reinforce evidence for a powerful connection between bacteria in the gut and the brain (SN: 4/2/16, p. 23).

After seven weeks of drinking water spiked with a cocktail of antibiotics, mice had fewer newborn nerve cells in a part of the hippocampus, a brain structure important for memory. The mice’s ability to remember previously seen objects also suffered.
Further experiments revealed one way bacteria can influence brain cell growth and memory. Injections of immune cells called Ly6Chi monocytes boosted the number of new nerve cells. Themonocytes appear to carry messages from gut to brain, Susanne Wolf of the Max Delbrück Center for Molecular Medicine in Berlin and colleagues found.

Exercise and probiotic treatment with eight types of live bacteria also increased the number of newborn nerve cells and improved memory in mice treated with antibiotics. The results help clarify the toll of prolonged antibiotic treatment, and hint at ways to fight back, the authors write.

Fruit fly’s giant sperm is quite an exaggeration

Forget it, peacocks. Nice try, elk. Sure, sexy feathers and antlers are showy, but the sperm of a fruit fly could be the most over-the-top, exaggerated male ornamentation of all.

In certain fruit fly species, such as Drosophila bifurca, males measuring just a few millimeters produce sperm with a tail as long as 5.8-centimeters, researchers report May 26 in Nature. Adjusted for body size, the disproportionately supersized sperm outdoes such exuberant body parts as pheasant display feathers, deer antlers, scarab beetle horns and the forward-grasping forceps of earwigs.
Fruit flies’ giant sperm have been challenging to explain, says study coauthor Scott Pitnick of Syracuse University in New York.

Now he and his colleagues propose that a complex interplay of male and female benefits has accelerated sperm length in a runaway-train scenario.

Males with longer sperm deliver fewer sperm, bucking a more-is-better trend. Yet, they still manage to transfer a few dozen to a few hundred per mating. And as newly arrived sperm compete to displace those already waiting in a female’s storage organ, longer is better. Fewer sperm per mating means females tend to mate more often, intensifying the sperm-vs.-sperm competition. Females that have the longest storage organs, which favor the longest sperm, benefit too: Males producing greater numbers of megasperm, the researchers found, tend to be the ones with good genes likely to produce robust offspring. “Sex,” says Pitnick, “is a powerful force.”
Among courtship-oriented body ornaments and weapons (red), the giant sperm of fruit flies (Drosophila) are the most disproportionately exaggerated, according to an index adjusted for body size. Higher numbers (bottom axis) indicate greater exaggeration.

Biologist Kate Rubins’ big dream takes her to the space station

When molecular biologist Kate Rubins blasts off from Kazakhstan on June 24, strapped into the Soyuz spacecraft bound for the International Space Station, the trip will cap off seven years of preparing — and 30 years of hoping.

As a child, Rubins plastered her Napa, Calif., bedroom with pictures of the space shuttle, proudly announcing her intention to be an astronaut. A week at Space Camp in Huntsville, Ala., in seventh grade cemented her vision. But by high school, she concluded that astronaut wasn’t “a realistic job,” she says.
Flash forward to 2009: Rubins is running a lab at the Whitehead Institute for Biomedical Research in Cambridge, Mass., focusing on virus-host interactions and viral genomics. A friend points out a NASA ad seeking astronaut candidates, and Rubins’ long-dormant obsession awakens. Since then, she has learned how to fly a T-38 jet, speak Russian to communicate with her cosmo-naut crewmates, conduct a spacewalk, operate the robotic arm on the ISS and even fix the habitable satellite’s toilet.

Joining NASA meant leaving her 14-person lab behind. But Rubins gained the rare opportunity to collaborate with dozens of scientists in fields as diverse as cell biology and astrophysics. On the space station, she’ll be “their hands, eyes and ears,” conducting about 100 experiments over five months.

She will, for instance, probe how heart cells behave when gravity doesn’t get in the way. And she’ll test a hand-held DNA sequencer, which reads out the genetic information stored in DNA and will be important to future missions looking for signatures of life on Mars.

At times, Rubins will be both experimenter and subject. In one study, she will observe bone cells in a lab dish, comparing their behavior with what happens in a simulated gravity-free environment on the ground. Because astronauts in space are vulnerable to rapid bone loss, CT scanning before and after the mission will also document changes in Rubins’ own hip bone.

Rubins is particularly eager to examine how liquid behaves in microgravity on a molecular scale. In 2013, Canadian astronaut Chris Hadfield created an Internet sensation when he demonstrated that wringing out a wet washcloth in space caused water to form a bubble that enveloped the cloth and his hands. “It’s incredibly bizarre,” Rubins says. Understanding how fluids move in test tubes in space will help NASA plan for Mars exploration, among other applications.
Before any of the research can begin, Rubins has to get off the ground. As treacherous as accelerating to 17,500 miles per hour may sound, she’s not worried.

“An important part of the training experience is making all the information and skills routine,” she says. She predicts that sitting down in the Soyuz spacecraft, pulling out her procedures and getting ready to launch will feel a lot like going into the lab and picking up a pipette — “a normal day at the office.”

Until the engines turn on, anyway. “I think it’s going to feel different when there’s a rocket underneath.”

Francis Crick’s good luck revolutionized biology

When Francis Crick was 31, he decided he needed to change his luck. As a graduate student in physics during World War II, his research hadn’t gone so well; his experiment was demolished by a bomb. To beat the war, he joined it, working on naval warfare mines for the British Admiralty.

After the war, he sought a new direction.

“There are lots of ways of being unlucky,” Crick told me in an interview in 1998. “One is sticking to things too long. Another is not adventuring at all.”

He decided to adventure.

Molecular biologists everywhere will celebrate that decision on June 8, the centennial of Crick’s birth, in Weston Favell, Northampton, England, in 1916.

“Crick was one of the central figures, one might say the central figure, in the molecular revolution that swept through biology in the latter half of the 20th century,” science historian Robert Olby wrote in a biographical sketch.

In 1953, at the University of Cambridge, Crick and his collaborator James Watson figured out how life’s most important molecule, deoxyribonucleic acid, was put together. DNA, the stuff that genes are made of, became the most famous of biological molecules. Today the image of its double helix structure symbolizes biology itself. It would be easy to make the case that discovering DNA’s structure was the single greatest event in the history of biology — and always will be. In 1962, Watson and Crick won the Nobel Prize for their work (which was, of course, greatly aided by X-ray diffraction imagery from Rosalind Franklin, who unfortunately died before the Nobel was awarded).

Crick’s DNA adventure began at a time when molecular biology was ripe for revolution. But Crick didn’t know that. His choice was lucky.
“I had no idea when I started that molecular biology would advance so fast,” he said. “No idea at all.”

In fact, Crick very nearly chose a different path. His interest in genes was equaled by his curiosity about the brain. Both were topics that he liked to gossip about.

“But I didn’t know enough about either subject,” he said. He just knew a little bit more about biochemistry.

“I thought ‘Well look, I have a training in physics and I know a bit of chemistry, I don’t know anything about the brain.’” So he decided it would be more sensible to start with genes.

“I thought that problem of what genes were and how they replicate and what they did would last me the rest of my life,” he said.

As it happened, genes did occupy him for a couple of decades. Crick made major contributions to elucidating the genetic code during that time. But he never forgot his interest in the brain, and more specifically, consciousness. In the 1970s, he moved from England to California, where he began consciousness research in San Diego at the Salk Institute for Biological Studies.

Consciousness turned out to be a much tougher problem than understanding genes. In retrospect, Crick could see why.

With genetics, “what really made the thing was the simplicity of the double helix. It wrote the whole research program,” he said. “It probably goes back to near the origin of life, when things had to be simple.” Consciousness appeared on the scene only much later, after the evolution of the brain’s vast complexity.

Nevertheless, Crick perceived parallels between genetics and consciousness as subjects for scientific inquiry. As the 20th century came to an end, he mused that consciousness as a concept remained vague — researchers did not all agree about what the word meant. The situation with genes had at one time been similar.

“In a sense people were just as vague about what genes were in the 1920s as they are now about consciousness,” Crick said. “It was exactly the same. The more professional people in the field, which was biochemistry at that time, thought that it was a problem that was too early to tackle. And I think they were right in the ’20s.”

At the end of the 20th century, research on consciousness found itself in much the same state.

“Everybody agrees that it’s an interesting question,” Crick said, “but there are two points of view among scientists: One is that it isn’t a scientific question and is best left to philosophers. And the other one is that, even if it’s a scientific question, it’s too early to tackle it now.”

Crick tackled it anyway. Until his death in 2004, he worked vigorously on the subject with his collaborator Christof Koch, making substantial inroads into identifying the brain activity associated with conscious awareness. Crick was not lucky enough to solve the problem of consciousness, but he perhaps brought the arrival of that solution a little closer.