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Benoit Guenard

Scientists Decode Bedbug Genome, and It Explains Why They’re So Hard to Kill

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Benoit Guenard

You may remember when “Don’t let the bedbugs bite” was just a cute thing parents said to their children. These days, though, it’s a real—albeit futile—warning. After decades of near eradication, the bedbug is back, and badder than ever. Now scientists say they’ve found clues to the bug’s tenacity buried in its genome and microbiome. The scientists published their findings in the journal Nature Communications.

Bedbugs are living fossils; their outward appearance has hardly changed throughout their long lineage, noted corresponding author George Amato in a press statement. “But despite their static look, we know that they continue to evolve, mostly in ways that make it harder for humans to dissociate with them. This work gives us the genetic basis to explore the bedbug’s basic biology and its adaptation to dense human environments.” 

Trying to understand bedbugs (Cimex lectularius) is more than just an intellectual exercise. As anyone who’s ever dealt with an infestation knows, they’re not just gross—they’re persistent. Clearing a home of bedbugs can be a painfully drawn-out and expensive process, in part because the little pests have developed a resistance to common pesticides.

The roots of that resistance lie in the bedbug’s genome, project co-leader Coby Schal said in a press statement. “The genome sequence shows genes that encode enzymes and other proteins that the bedbug can use to fight insecticides, whether by degrading them or by preventing them from penetrating its body."

And that’s not all they found. In teasing out the bedbug’s genetic code, the researchers saw explanations for many of the pest’s unique traits, like sex shielding. Male bedbugs are notoriously opportunistic about sex. They’ll jab their sharp, penis-like appendages at pretty much anything, including other males. And the sex itself isn’t pretty: The male bedbug stabs the female in the abdomen, then releases his sperm freely into the wound. To ease the sting of what scientists call “traumatic insemination,” female bedbugs have developed a kind of shielded funnel on their undersides. The protein that keeps that shield strong is called resilin, and it has its own code in the bedbug’s genome.

Not all the bedbug’s genes are bedbug genes; some of them came from other organisms, including the parasitic bacterium Wolbachia. "We don't know if the bacterium is co-opting the bedbug or if the bedbug is co-opting the bacterium,” Schal said in the press statement. “Very few of these bacterial genes are functional and we don't know what proteins they are producing. But it would be fascinating if bacterial genes that are useful to the bedbug, such as those involved in B vitamin metabolism, were incorporated into the bedbug genome."

The bug's microbiome had its own insights to offer. Researchers found the genes of more than 400 species of bacteria living on and in the bugs. The scientists theorize that these microbes help keep the bedbugs alive—which means there's a chance that targeted antibiotics to knock out these bacteria could eventually help us knock out the bedbugs, too.

Another finding concerns the bedbugs' ability to take in relatively large amounts of liquid (that is, blood) without exploding. They can balloon up to 200 percent their body size while feeding through a handy diuretic system. "Bedbugs must be able to shed that water while retaining the blood's nutrients," Schal said.

And then there’s the bedbug’s bite. The scientists found proteins that act as both anesthetics and anticoagulants that keep your blood flowing while keeping you from noticing.

Blech.

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Food
Researchers Pinpoint the Genes Behind the Durian's Foul Stench
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Durian is a popular fruit in parts of southeast Asia. It's also known for having the most putrid, off-putting odor of any item sold in the produce section. Even fans of durian know why the fruit gets a bad rap, but what exactly causes its divisive scent is less obvious. Determined to find the answer, a team of researchers funded by "a group of anonymous durian lovers" mapped the fruit's genome, as reported by the BBC.

The study, published in the journal Nature Genetics [PDF], contains data from the first-ever complete genetic mapping of a durian fruit. It confirms that durian's excess stinkiness comes from sulfur, a chemical element whose scent is often compared to that of rotten eggs.

Analysis of the fruit's chemical makeup has been done in the past, so the idea that sulfur is a major contributor to its signature smell is nothing new. What is new is the identification of the specific class of sulfur-producing genes. These genes pump out sulfur at a "turbocharged" rate, which explains why the stench is powerful enough to have durian banned in some public areas. It may seem like the smell is a defense mechanism to ward off predators, but the study authors write that it's meant to have the opposite effect. According to the paper, "it is possible that linking odor and ripening may provide an evolutionary advantage for durian in facilitating fruit dispersal." In other words, the scent attracts hungry primates that help spread the seeds of ripe durian fruits by consuming them.

The revelation opens the door to genetically modified durian that are tweaked to produce less sulfur and therefore have a milder taste and smell. But such a product would likely inspire outrage from the food's passionate fans. While the flavor profile has been compared to rotten garbage and dead animal meat, it's also been praised for its "overtones of hazelnut, apricot, caramelized banana, and egg custard" by those who appreciate its unique character.

[h/t BBC]

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Why DNA Is So Hard to Visualize
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Picture a strand of DNA and the image you see will likely be similar to the artist’s rendering above. The iconic twisted ladder, or double-helix structure, was first revealed in a photo captured by Rosalind Franklin in the 1950s, but this popular visualization only tells part of the story of DNA. In the video below, It’s Okay to Be Smart explains a more accurate way to imagine the blueprints of life.

Even with sophisticated lab equipment, DNA isn’t easy to study. That’s because a strand of the stuff is just 2 nanometers wide, which is smaller than a wavelength of light. Researchers can use electron microscopes to observe the genetic material or x-rays like Rosalind Franklin did, but even these tools paint a flawed picture. The best method scientists have come up with to visualize DNA as it exists inside our cells is computer modeling.

By rendering a 3D image of a genome on a computer, we can see that DNA isn’t just a bunch of free-floating squiggles. Most of the time the strands sit tightly wound in a well-organized web inside the nucleus. These balls of genes are efficient, packing 2 meters of DNA into a space just 10 millionths of a meter across. So if you ever see a giant sculpture inspired by an elegant double-helix structure, imagine it folded into a space smaller than a shoe box to get closer to the truth.

[h/t It’s Okay to Be Smart]

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