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How Deadly Would Extraterrestrial Bacteria Be to Humans?

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How deadly would a bacterium be to humans if it was brought from a completely different star system?

Drew Smith:

The chance that extraterrestrial bacteria would be deadly to humans is zero. Not just very, very small. Zero.

Pathogenesis requires intimacy. This intimacy is attained through millions of years of co-evolution. The need for intimacy is apparent when you look at how bacteria and viruses cause infections and disease.

Infection requires binding to a cell surface. Bacteria (and viruses) bind to human cells through proteins that recognize human proteins and carbohydrates. The structure of these human proteins and carbohydrates is, to a first approximation, arbitrary. There are an almost infinite number of permutations of them that could exist and work just fine. But only one does exist. The chance that an alien bacteria would have evolved to stick to that protein is infinitesimally small.

Even if this alien bacterium were able to stick to a cell surface, this alone would not establish an infection. Infecting bacteria secrete all kinds of toxins and virulence factors. These toxins and factors bind to specific human proteins. They block or modify their activity in ways that degrade cells and tissues, releasing nutrients that the bacteria can feed upon.

Again, the target proteins have fairly arbitrary structures. They are the result of billions of years of evolutionary history and their precise structure—and even their existence is not at all predictable. The chance that an alien bacterium would have evolved toxins that precisely target them is infinitesimally small.

Pathogenicity is extremely rare on Earth. There are millions, perhaps billions, of species of bacteria. The number of potential human pathogens among them is very small, no more than a couple hundred. And only a couple dozen are able to infect otherwise healthy humans. These are bacteria that have been with us for millions of years, evolving as we evolve, becoming intimately familiar with our proteins, our cells, our immune systems.

This knowledge is stamped into their genomes; it is a diary of their long association with us. It is not a book that could be written in an alien language. Alien bacteria are no more likely to be human pathogens than intelligent aliens are likely to speak Urdu as their native tongue. It just isn’t possible.

This post originally appeared on Quora. Click here to view.

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entertainment
‘Total Eclipse of the Heart’ Could Have Been a Meat Loaf Song
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Imagine a world in which Bonnie Tyler was not the star performer on the Royal Caribbean Total Eclipse Cruise. Imagine if, instead, as the moon crossed in front of the sun in the path of totality on August 21, 2017, the performer belting out the 1983 hit for cruise ship stargazers was Meat Loaf?

It could have been. Because yes, as Atlas Obscura informs us, the song was originally written for the bestselling rocker (and actor) of Bat Out of Hell fame, not the husky-voiced Welsh singer. Meat Loaf had worked on his 1977 record Bat Out of Hell with Jim Steinman, the composer and producer who would go on to work with the likes of Celine Dion and Barbra Streisand (oddly enough, he also composed Hulk Hogan’s theme song on an album released by the WWE). “Total Eclipse of the Heart” was meant for Meat Loaf’s follow-up album to Bat Out of Hell.

But Meat Loaf’s fruitful collaboration with Steinman was about to end. In the wake of his bestselling record, the artist was going through a rough patch, mentally, financially, and in terms of his singing ability. And the composer wasn’t about to stick around. As Steinman would tell CD Review magazine in 1989 (an article he has since posted on his personal website), "Basically I only stopped working with him because he lost his voice as far as I was concerned. It was his voice I was friends with really.” Harsh, Jim, harsh.

Steinman began working with Bonnie Tyler in 1982, and in 1983, she released her fifth album, Faster Than the Speed of Night, including “Total Eclipse of the Heart.” It sold 6 million copies.

Tyler and Steinman both dispute that the song was written specifically for Meat Loaf. “Meat Loaf was apparently very annoyed that Jim gave that to me,” she told The Irish Times in 2014. “But Jim said he didn’t write it for Meat Loaf, that he only finished it after meeting me.”

There isn’t a whole lot of bad blood between the two singers, though. In 1989, they released a joint compilation album: Heaven and Hell.

[h/t Atlas Obscura]

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History
13 Vintage Photos of People Watching Solar Eclipses
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Ahead of the total solar eclipse on August 21, 2017, take a peek at these old photos of Earthlings with their eyes glued to the skies.

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