With delicate hues of purple and pink, a lab technique called gram staining has reliably characterized bacteria for more than a century. Yet many scientists are mistaken about why the vivid method works, new research finds.
Contrary to standard scientific texts, the purple dye called crystal violet, a main ingredient in gram staining, does not actually enter bacterial cells, researchers report April 27 in ACS Chemical Biology. Instead, the dye gets trapped in a tight package of sugar-filled polymers, called peptidoglycan, which envelops bacterial cells. The thickness and integrity of the sweet bacterial armor determines whether crystal violet leaves a cell purple or not. That royal shade, or lack of it, reveals a cell’s type of outer structure. Published by Hans Christian Gram in 1884, gram staining distinguishes gram-positive bacteria (purple) from gram-negative bacteria (pink). Gram-positive critters, such as staph, have a thick peptidoglycan layer that shields an inner cellular membrane. Gram-negative cells, such as E. coli, have a thin peptidoglycan layer sandwiched between a porous outer membrane and an inner membrane. Microbiologists thought that crystal violet could easily pass through membranes and into both cell types, says microbiologist Moselio Schaechter, an emeritus professor at Tufts University School of Medicine in Boston. A subsequent harsh shower of alcohol could then corrode both cell types’ membranes. This particularly clobbers gram-negative cells’ outer structures, including the thin layer of peptidoglycan which is bound to the outer membrane, allowing the purple dye to flush away. Meanwhile, gram-positive cells’ sturdier layer of peptidoglycan warps a bit but stays largely intact, keeping the microbes purple. The colorless gram-negative cells can then be stained with another dye, such as safranine, tinting the cells pink.
But that explanation is incorrect, says physical chemist Michael Wilhelm of Temple University in Philadelphia. Using a recently developed spectroscopy technique that monitors molecules as they traverse membranes, Wilhelm and colleagues found that crystal violet doesn’t cross the inner membrane of either cell type.
Instead, crystal violet seeps into the cracks of peptidoglycan, which acts like a “brick wall of sugar,” Wilhelm says. A gram-negative cell’s thin wall crumbles in the alcohol wash and releases the dye, he explains. In gram-positive cells, crystal violet slowly drains from the thick peptidoglycan barrier, but not quickly enough to leave the cell colorless during the protocol.
The study is fascinating, says microbiologist Rita Moyes of Texas A&M University in College Station. Scientists should continue to use new technologies to study old techniques, she says.
“Who’d have thought gram stain lecture material needed an update?” says microbiologist Mark Forsyth of the College of William & Mary in Williamsburg, Va. But, he says, “it may take a while to convince old professors like me to actually change their shtick about how this historic stain works.”
Sci-fi novels and films like Gattaca no longer have a monopoly on genetically engineered humans. Real research scripts about editing the human genome are now appearing in scientific and medical journals. But the reviews are mixed.
In Gattaca, nearly everyone was genetically altered, their DNA adjusted to prevent disease, enhance intelligence and make them look good. Today, only people treated with gene therapy have genetically engineered DNA. But powerful new gene editing tools could expand the scope of DNA alteration, forever changing humans’ genetic destiny.
Not everyone thinks scientists should wield that power. Kindling the debate is a report by scientists from Sun Yat-sen University in Guangzhou, China, who have edited a gene in fertilized human eggs, called zygotes. The team used new gene editing technology known as the CRISPR/Cas9 system. That technology can precisely snip out a disease-causing mutation and replace it with healthy DNA. CRISPR/Cas9 has edited DNA in stem cells and cancer cells in humans. Researchers have also deployed the molecules to engineer other animals, including mice and monkeys (SN Online: 3/31/14; SN: 3/8/14, p. 7). But it had never before been used to alter human embryos. The team’s results, reported April 18 in Protein & Cell, sparked a flurry of headlines because their experiment modified human germline tissue (SN Online: 4/23/15). While most people think it is all right to fix faulty genes in mature body, or somatic, cells, tinkering with the germ line — eggs, sperm or tissues that produce those reproductive cells — crosses an ethical line for many. Germline changes can be passed on to future generations, and critics worry that allowing genetic engineering to correct diseases in germline tissues could pave the way for creating designer babies or other abuses that will persist forever.
“How do you draw a clear, meaningful line between therapy and enhancement?” ponders Marcy Darnovsky, executive director of the Center for Genetics and Society in Berkeley, Calif. About 40 countries ban or restrict such inherited DNA modifications.
Rumors about human germline editing experiments prompted scientists to gather in January in Napa, Calif. Discussions there led two groups to publish recommendations. One group, reporting March 26 in Nature, called for scientists to “agree not to modify the DNA of human reproductive cells,” including the nonviable zygotes used in the Chinese study. A second group, writing in Science April 3, called for a moratorium on the clinical use of human germline engineering, but stopped short of saying the technology shouldn’t be used in research. Those researchers say that while CRISPR technology is still too primitive for safe use in patients, further research is needed to improve it. But those publishing in Nature disagreed.
“Are there ever any therapeutic uses that would demand … modification of the human germ line? We don’t think there are any,” says Edward Lanphier, president of Sangamo BioSciences in Richmond, Calif. “Modifying the germ line is crossing the line that most countries on our planet have said is never appropriate to cross.”
If germline editing is never going to be allowed, there is no reason to conduct research using human embryos or reproductive cells, he says. Sangamo BioSciences is developing gene editing tools for use in somatic cells, an approach that germline editing might render unneeded. Lanphier denies that financial interests play a role in his objection to germline editing.
Other researchers, including Harvard University geneticist George Church, think germline editing may well be the only solution for some people with rare, inherited diseases. “What people want is safety and efficacy,” says Church. “If you ban experiments aimed at improving safety and efficacy, we’ll never get there.”
The zygote experiments certainly demonstrate that CRISPR technology is not ready for daily use yet. The researchers attempted to edit the beta globin, or HBB, gene. Mutations in that gene cause the inherited blood disorder beta-thalassemia. CRISPR/Cas9 molecules were engineered to seek out HBB and cut it where a piece of single-stranded DNA could heal the breach, creating a copy of the gene without mutations. That strategy succeeded in only four of the 86 embryos that the researchers attempted to edit. Those edited embryos contained a mix of cells, some with the gene edited and some without.
In an additional seven embryos, the HBB gene cut was repaired using the nearby HBD gene instead of the single-stranded DNA. The researchers also found that the molecular scissors snipped other genes that the researchers never intended to touch.
“Taken together, our work highlights the pressing need to further improve the fidelity and specificity of the CRISPR/Cas9 platform, a prerequisite for any clinical applications,” the researchers wrote.
The Chinese researchers crossed no ethical lines, Church contends. “They tried to dot i’s and cross t’s on the ethical questions.” The zygotes could not develop into a person, for instance: They had three sets of chromosomes, having been fertilized by two sperm in lab dishes.
Viable or not, germline cells should be off limits, says Darnovsky. She opposes all types of human germline modification, including a procedure approved in the United Kingdom in February for preventing mitochondrial diseases. The U.K. prohibits all other germline editing.
Mitochondria, the power plants that churn out energy in a cell, each carry a circle of DNA containing genes necessary for the organelle’s function. Mothers pass mitochondria on to their offspring through the egg. About one in 5,000 babies worldwide are born with mitochondrial DNA mutations that cause disease, particularly in energy-greedy organs such as the muscles, heart and brain.
Such diseases could be circumvented with a germline editing method known as mitochondrial replacement therapy (SN: 11/17/12, p. 5). In a procedure pioneered by scientists at Oregon Health & Science University, researchers first pluck the nucleus, where the bulk of genetic instructions for making a person are stored, out of the egg of a woman who carries mutant mitochondria. That nucleus is then inserted into a donor egg containing healthy mitochondria. The transfer would produce a person with three parents; most of their genes inherited from the mother and father, with mitochondrial DNA from the anonymous donor. The first babies produced through that technology could be born in the U.K. next year.
Yet another new gene-editing technique could eliminate the need to use donor eggs by specifically destroying only disease-carrying mitochondria, researchers from the Salk Institute for Biological Studies in La Jolla, Calif., reported April 23 in Cell (SN Online: 4/23/15).
Such unproven technologies shouldn’t be attempted when alternatives already exist, Darnovsky says, such as screening embryos created through in vitro fertilization and discarding those likely to develop the disease.
But banning genome-altering technology could leave people with genetic diseases, and society in general, in the lurch, says molecular biologist Matthew Porteus of Stanford University.
“There is no benefit in my mind of having a child born with a devastating genetic disease,” he says.
Alternatives to germline editing come with their own ethical quandaries, he says. Gene testing of embryos may require creating a dozen or more embryos before finding one that doesn’t carry the disease. The rest of the embryos would be destroyed. Many people find that prospect ethically questionable.
But that doesn’t argue for sliding into Gattaca territory, where genetic modification becomes mandatory. “If we get there,” says Porteus, “we’ve really screwed up.”
An unusual blast of radio waves from deep space had a sense of rhythm. Over the few seconds in December 2019 when the burst was detected, it kept a steady beat. That tempo holds clues to the potential origin of the mysterious outburst, one of a class of flares called fast radio bursts.
Of the hundreds of previously detected fast radio bursts, most last for mere milliseconds. But this one persisted for roughly three seconds, Daniele Michilli and colleagues report in the July 14 Nature. The burst consisted of multiple brief pulses, repeating about every two-tenths of a second. Scientists have previously observed fast radio bursts that repeat with a delay of minutes or days (SN: 3/2/16). “With this one it was a train of [pulses] one after the other, a heartbeat, like, ‘boom boom boom boom,’” says Michilli, an astronomer at MIT.
That makes this fast radio burst very special, says astrophysicist Bing Zhang of the University of Nevada, Las Vegas, who was not involved with the research. Compared with other fast radio bursts, “this is a different animal.”
Scientists still don’t know how fast radio bursts are generated, but evidence has been building that they are associated with ultradense, spinning dead stars called neutron stars and, in particular, highly magnetic neutron stars called magnetars (SN: 6/4/20).
The steady repetition rate hints at what may have caused this particular blast, discovered by the Canadian Hydrogen Intensity Mapping Experiment, a radio telescope in British Columbia.
Only certain types of cosmic processes produce such metronome-like signals. Neutron stars, for example, can appear to pulse as they spin, because they emit beams of radio waves that can sweep past Earth at regular intervals. Neutron stars tend to have tempos similar to that of the pulsating fast radio burst. But that burst was much more luminous than normal neutron star pulses, suggesting some unknown process would need to have amped up the emission.
Another idea is that large outbursts on magnetars could cause starquakes that jostle those stars’ solid crusts, generating regular barrages of radio waves. The rhythmic burst’s pulsing “is sort of consistent with a frequency with which we expect that magnetars could be shaking,” says astrophysicist Cecilia Chirenti of the University of Maryland in College Park, who was not involved with the new study.
Or the pulsing might result from two neutron stars that orbit one another. Outbursts could occur at regular points in that orbit, when the magnetic regions that surround each neutron star interact.
Scientists don’t know if all fast radio bursts are generated in the same way. An outlier like this one might have a different origin story than a more standard, one-off blast. That means it’s hard to make conclusions about other fast radio bursts, Zhang says. “Whatever we can derive from this one, I would not easily extrapolate to the other guys.”
Pocket gophers certainly don’t qualify as card-carrying 4-H members, but the rodents might be farming roots in the open air of their moist, nutrient-rich tunnels.
The gophers subsist mostly on roots encountered in the tunnels that the rodents excavate. But the local terrain doesn’t always provide enough roots to sustain gophers, two researchers report in the July 11 Current Biology. To make up the deficit, the gophers practice a simple type of agriculture by creating conditions that promote more root growth, suggest ecologist Jack Putz of the University of Florida in Gainesville and his former zoology undergraduate student Veronica Selden. But some scientists think it’s a stretch to call the rodents’ activity farming. Gophers aren’t actively working the soil, these researchers say, but inadvertently altering the environment as the rodents eat and poop their way around — much like all animals do.
Tunnel digging takes a lot of energy — up to 3,400 times as much as walking along the surface for gophers. To see how the critters were getting all this energy, Selden and Putz in 2021 began investigating the tunnels of southeastern pocket gophers (Geomys pinetis) in an area being restored to longleaf pine savanna in Florida that Putz partially owns.
The pair took root samples from soil adjacent to 12 gopher tunnels and extrapolated how much root mass a gopher would encounter as it excavated a meter of tunnel. Then the researchers calculated the amount of energy that those roots would provide.
“We were able to compare energy cost versus gain, and found that on average there is a deficit, with about half the cost of digging being unaccounted for,” Selden says.
Upon examining some tunnels, Selden and Putz saw gopher feces spread through the interior along with signs of little bites taken out of roots and churning of the soil.
The gophers, the researchers conclude, provide conditions that favor root growth by spreading their own waste as fertilizer, aerating the soil and repeatedly nibbling on roots to encourage new sprouting. “All of these activities encourage root growth, and once the roots grow into the tunnels, the gophers crop the roots,” Selden says. She and Putz say that this amounts to a rudimentary form of farming. If so, gophers would be the first nonhuman mammals to be recognized as farmers, Putz says. Other organisms, such as some insects, also farm food and started doing so much earlier than humans (SN: 4/23/20).
But the study has its skeptics. “I don’t really think you can call it farming per the human definition. All herbivores eat plants, and everybody poops,” says J.T. Pynne, a wildlife biologist at the Georgia Wildlife Federation in Covington who studies southeastern pocket gophers. So the root nibbling and tunnel feces might not be signs of agriculture, just gophers doing what all animals do.
Evolutionary biologist Ulrich Mueller agrees. “If we accept the tenuous evidence presented in the Selden article as evidence for farming … then most mammals and most birds are farmers because each of them accidentally have also some beneficial effects on some plants that these mammals or birds also feed on,” he says.
Not only that, but the study is also dangerous, says Mueller, of the University of Texas at Austin. The public will see through “the shallowness of the data,” he says, and will conclude that science is “just a bunch of storytelling, eroding general trust in science.”
For her part, Selden says she understands that because gophers don’t plant their crops, not everyone is comfortable calling them farmers. Still, she argues that “what qualifies the gophers as farmers and sets them apart from, say, cattle, which incidentally fertilize the grass they eat with their wastes, is that gophers cultivate and maintain this ideal environment for roots to grow into.”
At the very least, Putz says, he hopes their research makes people kinder toward the rodents. “If you go to the web and put in ‘pocket gopher,’ you’ll see more ways to kill them than you can count.”
Humans have long tried to wrangle water. We’ve straightened once-meandering rivers for shipping purposes. We’ve constructed levees along rivers and lakes to protect people from flooding. We’ve erected entire cities on drained and filled-in wetlands. We’ve built dams on rivers to hoard water for later use.
“Water seems malleable, cooperative, willing to flow where we direct it,” environmental journalist Erica Gies writes in Water Always Wins. But it’s not, she argues.
Levees, which narrow channels causing water to flow higher and faster, nearly always break. Cities on former wetlands flood regularly — often catastrophically. Dams starve downstream environs of sediment needed to protect coastal areas against rising seas. Straightened streams flow faster than meandering ones, scouring away riverbed ecosystems and giving water less time to seep downward and replenish groundwater supplies.
In addition to laying out this damage done by supposed water control, Gies takes readers on a hopeful global tour of solutions to these woes. Along the way, she introduces “water detectives”— scientists, engineers, urban planners and many others who, instead of trying to control water, ask: What does water want? These water detectives have found ways to give the slippery substance the time and space it needs to trickle underground. Around Seattle’s Thornton Creek, for instance, reclaimed land now allows for regular flooding, which has rejuvenated depleted riverbed habitat and created an urban oasis. In California’s Central Valley, scientists want to find ways to shunt unpolluted stormwater into ancient, sediment-filled subsurface canyons that make ideal aquifers. Feeding groundwater supplies will in turn nourish rivers from below, helping to maintain water levels and ecosystems.
While some people are exploring new ways to manage water, others are leaning on ancestral knowledge. Without the use of hydrologic mapping tools, Indigenous peoples of the Andes have a detailed understanding of the plumbing that links surface waters with underground storage. Researchers in Peru are now studying Indigenous methods of water storage, which don’t require dams, in hopes of ensuring a steady flow of water to Lima — Peru’s populous capital that’s periodically afflicted by water scarcity. These studies may help convince those steeped in concrete-centric solutions to try something new. “Decision makers come from a culture of concrete,” Gies writes, in which dams, pipes and desalination plants are standard.
Understanding how to work with, not against, water will help humankind weather this age of drought and deluge that’s being exacerbated by climate change. Controlling water, Gies convincingly argues, is an illusion. Instead, we must learn to live within our water means because water will undoubtedly win.
Biologist Martin Dančák didn’t set out to find a plant species new to science. But on a hike through a rainforest in Borneo, he and colleagues stumbled on a subterranean surprise.
Hidden beneath the soil and inside dark, mossy pockets below tree roots, carnivorous pitcher plants dangled their deathtraps underground. The pitchers can look like hollow eggplants and probably lure unsuspecting prey into their sewer hole-like traps. Once an ant or a beetle steps in, the insect falls to its death, drowning in a stew of digestive juices (SN: 11/22/16). Until now, scientists had never observed pitcher plants with traps almost exclusively entombed in earth. “We were, of course, astonished as nobody would expect that a pitcher plant with underground traps could exist,” says Dančák, of Palacký University in Olomouc, Czech Republic.
That’s because pitchers tend to be fragile. But the new species’ hidden traps have fleshy walls that may help them push against soil as they grow underground, Dančák and colleagues report June 23 in PhytoKeys. Because the buried pitchers stay concealed from sight, the team named the species Nepenthes pudica, a nod to the Latin word for bashful.
The work “highlights how much biodiversity still exists that we haven’t fully discovered,” says Leonora Bittleston, a biologist at Boise State University in Idaho who was not involved with the study. It’s possible that other pitcher plant species may have traps lurking underground and scientists just haven’t noticed yet, she says. “I think a lot of people don’t really dig down.”
The next generation of dark matter detectors has arrived.
A massive new effort to detect the elusive substance has reported its first results. Following a time-honored tradition of dark matter hunters, the experiment, called LZ, didn’t find dark matter. But it has done that better than ever before, physicists report July 7 in a virtual webinar and a paper posted on LZ’s website. And with several additional years of data-taking planned from LZ and other experiments like it, physicists are hopeful they’ll finally get a glimpse of dark matter. “Dark matter remains one of the biggest mysteries in particle physics today,” LZ spokesperson Hugh Lippincott, a physicist at the University of California, Santa Barbara said during the webinar.
LZ, or LUX-ZEPLIN, aims to discover the unidentified particles that are thought to make up most of the universe’s matter. Although no one has ever conclusively detected a particle of dark matter, its influence on the universe can be seen in the motions of stars and galaxies, and via other cosmic observations (SN: 7/24/18).
Located about 1.5 kilometers underground at the Sanford Underground Research Facility in Lead, S.D., the detector is filled with 10 metric tons of liquid xenon. If dark matter particles crash into the nuclei of any of those xenon atoms, they would produce flashes of light that the detector would pick up.
The LZ experiment is one of a new generation of bigger, badder dark matter detectors based on liquid xenon, which also includes XENONnT in Gran Sasso National Laboratory in Italy and PandaX-4T in the China Jinping Underground Laboratory. The experiments aim to detect a theorized type of dark matter called Weakly Interacting Massive Particles, or WIMPs (SN: 12/13/16). Scientists scaled up the search to allow for a better chance of spying the particles, with each detector containing multiple tons of liquid xenon.
Using only about 60 days’ worth of data, LZ has already surpassed earlier efforts to pin down WIMPs (SN: 5/28/18). “It’s really impressive what they’ve been able to pull off; it’s a technological marvel,” says theoretical physicist Dan Hooper of Fermilab in Batavia, Ill, who was not involved with the study.
Although LZ’s search came up empty, “the way something’s going to be discovered is when you have multiple years in a row of running,” says LZ collaborator Matthew Szydagis, a physicist at the University at Albany in New York. LZ is expected to run for about five years, and data from that extended period may provide physicists’ best chance to find the particles.
Now that the detector has proven its potential, says LZ physicist Kevin Lesko of Lawrence Berkeley National Laboratory in California, “we’re excited about what we’re going to see.”
Tyrannosaurus rex’s tiny arms have launched a thousand sarcastic memes: I love you this much; can you pass the salt?; row, row, row your … oh.
But back off, snarky jokesters. A newfound species of big-headed carnivorous dinosaur with tiny forelimbs suggests those arms weren’t just an evolutionary punchline. Arm reduction — alongside giant heads — evolved independently in different dinosaur lineages, researchers report July 7 in Current Biology.
Meraxes gigas, named for a dragon in George R. R. Martin’s “A Song of Ice and Fire” book series, lived between 100 million and 90 million years ago in what’s now Argentina, says Juan Canale, a paleontologist with the country’s CONICET research network who is based in Buenos Aires. Despite the resemblance to T. rex, M. gigas wasn’t a tyrannosaur; it was a carcharodontosaur — a member of a distantly related, lesser-known group of predatory theropod dinosaurs. M. gigas went extinct nearly 20 million years before T. rex walked on Earth. The M. gigas individual described by Canale and colleagues was about 45 years old and weighed more than four metric tons when it died, they estimate. The fossilized specimen is about 11 meters long, and its skull is heavily ornamented with crests and bumps and tiny hornlets, ornamentations that probably helped attract mates.
Why these dinosaurs had such tiny arms is an enduring mystery. They weren’t for hunting: Both T. rex and M. gigas used their massive heads to hunt prey (SN: 10/22/18). The arms may have shrunk so they were out of the way during the frenzy of group feeding on carcasses.
But, Canale says, M. gigas’ arms were surprisingly muscular, suggesting they were more than just an inconvenient limb. One possibility is that the arms helped lift the animal from a reclining to a standing position. Another is that they aided in mating — perhaps showing a mate some love.
Getting a COVID-19 test has become a regular part of many college students’ lives. That ritual may protect not just those students’ classmates and professors but also their municipal bus drivers, neighbors and other members of the local community, a new study suggests.
Counties where colleges and universities did COVID-19 testing saw fewer COVID-19 cases and deaths than ones with schools that did not do any testing in the fall of 2020, researchers report June 23 in PLOS Digital Health. While previous analyses have shown that counties with colleges that brought students back to campus had more COVID-19 cases than those that continued online instruction, this is the first look at the impact of campus testing on those communities on a national scale (SN: 2/23/21). “It’s tough to think of universities as just silos within cities; it’s just much more permeable than that,” says Brennan Klein, a network scientist at Northeastern University in Boston.
Colleges that tested their students generally did not see significantly lower case counts than schools that didn’t do testing, Klein and his colleagues found. But the communities surrounding these schools did see fewer cases and deaths. That’s because towns with colleges conducting regular testing had a more accurate sense of how much COVID-19 was circulating in their communities, Klein says, which allowed those towns to understand the risk level and put masking policies and other mitigation strategies in place.
The results highlight the crucial role testing can continue to play as students return to campus this fall, says Sam Scarpino, vice president of pathogen surveillance at the Rockefeller Foundation’s Pandemic Prevention Institute in Washington, D.C. Testing “may not be optional in the fall if we want to keep colleges and universities open safely,” he says. Finding a flight path As SARS-CoV-2, the virus that causes COVID-19 rapidly spread around the world in the spring of 2020, it had a swift impact on U.S. college students. Most were abruptly sent home from their dorm rooms, lecture halls, study abroad programs and even spring break outings to spend what would be the remainder of the semester online. And with the start of the fall semester just months away, schools were “flying blind” as to how to bring students back to campus safely, Klein says.
That fall, Klein, Scarpino and their collaborators began to put together a potential flight path for schools by collecting data from COVID-19 dashboards created by universities and the counties surrounding those schools to track cases. The researchers classified schools based on whether they had opted for entirely online learning or in-person teaching. They then divided the schools with in-person learning based on whether they did any testing.
It’s not a perfect comparison, Klein says, because this method groups schools that did one round of testing with those that did consistent surveillance testing. But the team’s analyses still generally show how colleges’ pandemic response impacted their local communities.
Overall, counties with colleges saw more cases and deaths than counties without schools. However, testing helped minimize the increase in cases and deaths. During the fall semester, from August to December, counties with colleges that did testing saw on average 14 fewer deaths per 100,000 people than counties with colleges that brought students back with no testing — 56 deaths per 100,000 versus about 70. The University of Massachusetts Amherst, with nearly 30,000 undergraduate and graduate students in 2020, is one case study of the value of the testing, Klein says. Throughout the fall semester, the school tested students twice a week. That meant that three times as many tests occurred in the city of Amherst than in neighboring cities, he says. For much of the fall and winter, Amherst had fewer COVID-19 cases per 1,000 residents than its neighboring counties and statewide averages.
Once students left for winter break, campus testing stopped – so overall local testing dropped. When students returned for spring semester in February 2021, area cases spiked — possibly driven by students bringing the coronavirus back from their travels and by being exposed to local residents whose cases may have been missed due to the drop in local testing. Students returned “to a town that has more COVID than they realize” Klein says.
Renewed campus testing not only picked up the spike but quickly prompted mitigation strategies. The university moved classes to Zoom and asked students to remain in their rooms, at one point even telling them that they should not go on walks outdoors. By mid-March, the university reduced the spread of cases on campus and the town once again had a lower COVID-19 case rate than its neighbors for the remainder of the semester, the team found.
The value of testing It’s helpful to know that testing overall helped protect local communities, says David Paltiel, a public health researcher at the Yale School of Public Health who was not involved with the study. Paltiel was one of the first researchers to call for routine testing on college campuses, regardless of whether students had symptoms.
“I believe that testing and masking and all those things probably were really useful, because in the fall of 2020 we didn’t have a vaccine yet,” he says. Quickly identifying cases and isolating affected students, he adds, was key at the time. But each school is unique, he says, and the benefit of testing probably varied between schools. And today, two and a half years into the pandemic, the cost-benefit calculation is different now that vaccines are widely available and schools are faced with newer variants of SARS-CoV-2. Some of those variants spread so quickly that even testing twice a week may not catch all cases on campus quickly enough to stop their spread, he says.
As colleges and universities prepare for the fall 2022 semester, he would recommend schools consider testing students as they return to campus with less frequent follow-up surveillance testing to “make sure things aren’t spinning crazy out of control.”
Still, the study shows that regular campus testing can benefit the broader community, Scarpino says. In fact, he hopes to capitalize on the interest in testing for COVID-19 to roll out more expansive public health testing for multiple respiratory viruses, including the flu, in places like college campuses. In addition to PCR tests — the kind that involve sticking a swab up your nose — such efforts might also analyze wastewater and air within buildings for pathogens (SN: 05/28/20).
Unchecked coronavirus transmission continues to disrupt lives — in the United States and globally — and new variants will continue to emerge, he says. “We need to be prepared for another surge of SARS-CoV-2 in the fall when the schools reopen, and we’re back in respiratory season.”
Emerald jewel wasps know what cockroach brains feel like.
This comes in handy when a female wasp needs to turn a cockroach into an obedient zombie that will host her larvae and serve as dinner. First, the wasp plunges its stinger into the cockroach’s midsection to briefly paralyze the legs. Next comes a more delicate operation: stinging the head to deliver a dose of venom to specific nerve cells in the brain, which gives the wasp control over where its victim goes. But how does a wasp know when it’s reached the brain? The stinger’s tip is a sensory probe. In experiments using brainless cockroaches, a wasp will sting the head over and over again, searching fruitlessly for its desired target.
A brain-feeling stinger is just one example of the myriad ways animals sense the world around them. We humans tend to think the world is as we perceive it. But for everything that we can see, smell, taste, hear or touch, there’s so much more that we’re oblivious to.
In An Immense World, science journalist Ed Yong introduces that hidden world and the concept of Umwelt, a German word that refers to the parts of the environment an animal senses and experiences. Every creature has its own Umwelt. In a room filled with different types of organisms, or even multiple people, each individual would experience that shared atmosphere in wholly different ways.
Yong eases readers into the truly immense world of senses by starting with ones that we are intimately familiar with. In some cases, he tests the limits of his own abilities. Dog noses, for instance, are better than human noses at sniffing out a scent long after the source is gone, as Yong demonstrates. While crawling around on his hands and knees with his eyes closed, he was able to track a chocolate-scented string that a researcher had put on the ground. But he lost the scent when the string was removed. That wouldn’t happen to a dog. It would pick up the trace, string or no string. In exploring the vast sensory world, it helps to have a good imagination, as even familiar senses can seem quite strange. Scallops, for instance, have eyes and somehow “see” despite having a crude brain that can’t process the images. Crickets have hairs that are so responsive to an approaching spider that trying to make the hairs more sensitive might break the rules of physics. A blind Ecuadorian catfish senses raging water with durable teeth that cover its skin. The animal uses the dentures to find calmer waters.
Going through these imagination warm-up exercises makes it somewhat easier to ponder what it might be like to be an echolocating bat, a bird that detects magnetic fields or a fish that communicates using electricity. Yong’s vivid descriptions also help readers fathom these senses: “A river full of electric fish must be like a cocktail party where no one ever shuts up, even when their mouths are full.” In a forest, foliage may seem largely silent, but some insects “talk” through plant stems using vibration. With headphones hooked up to plants so that scientists can listen in, “chirping cicadas sound like cows and katydids sound like revving chainsaws.”
For all the book’s wonder, the last chapter brings readers crashing back to today’s reality. Humans are polluting animals’ Umwelten; we’re forcing animals to exist in environments contaminated with human-made stimuli. And the consequences can be deadly, Yong warns. Adding artificial light in the darkness of night is killing birds and insects (SN: 8/31/21). Making environments louder is masking the sounds of predators and forcing prey to spend more time keeping an eye out than eating (SN: 5/4/17). “We are closer than ever to understanding what it is like to be another animal,” Yong writes, “but we have made it harder than ever for other animals to be.”
Since each of us has our own Umwelt, fully understanding the foreign worlds of animals is close to impossible, Yong writes. How do we know, for instance, which animals feel pain? Researchers can dissect the signals or stimuli an animal might receive. But what that creature experiences often remains a mystery.
