Do Bacteria Have Bacteria?

iStock
iStock

Drew Smith:

Do bacteria have bacteria? Yes.

We know that bacteria range in size from 0.2 micrometers to nearly one millimeter. That’s more than a thousand-fold difference, easily enough to accommodate a small bacterium inside a larger one.

Nothing forbids bacteria from invading other bacteria, and in biology, that which is not forbidden is inevitable.

We have at least one example: Like many mealybugs, Planococcus citri has a bacterial endosymbiont, in this case the β-proteobacterium Tremblaya princeps. And this endosymbiont in turn has the γ-proteobacterium Moranella endobia living inside it. See for yourself:

Fluorescent In-Situ Hybridization confirming that intrabacterial symbionts reside inside Tremblaya cells in (A) M. hirsutus and (B) P. marginatus mealybugs. Tremblaya cells are in green, and γ-proteobacterial symbionts are in red. (Scale bar: 10 μm.)
Fluorescent In-Situ Hybridization confirming that intrabacterial symbionts reside inside Tremblaya cells in (A) M. hirsutus and (B) P. marginatus mealybugs. Tremblaya cells are in green, and γ-proteobacterial symbionts are in red. (Scale bar: 10 μm.)

I don’t know of examples of free-living bacteria hosting other bacteria within them, but that reflects either my ignorance or the likelihood that we haven’t looked hard enough for them. I’m sure they are out there.

Most (not all) scientists studying the origin of eukaryotic cells believe that they are descended from Archaea.

All scientists accept that the mitochondria which live inside eukaryotic cells are descendants of invasive alpha-proteobacteria. What’s not clear is whether archeal cells became eukaryotic in nature—that is, acquired internal membranes and transport systems—before or after acquiring mitochondria. The two scenarios can be sketched out like this:


The two hypotheses on the origin of eukaryotes:

(A) Archaezoan hypothesis.

(B) Symbiotic hypothesis.

The shapes within the eukaryotic cell denote the nucleus, the endomembrane system, and the cytoskeleton. The irregular gray shape denotes a putative wall-less archaeon that could have been the host of the alpha-proteobacterial endosymbiont, whereas the oblong red shape denotes a typical archaeon with a cell wall. A: archaea; B: bacteria; E: eukaryote; LUCA: last universal common ancestor of cellular life forms; LECA: last eukaryotic common ancestor; E-arch: putative archaezoan (primitive amitochondrial eukaryote); E-mit: primitive mitochondrial eukaryote; alpha:alpha-proteobacterium, ancestor of the mitochondrion.

The Archaezoan hypothesis has been given a bit of a boost by the discovery of Lokiarcheota. This complex Archaean has genes for phagocytosis, intracellular membrane formation and intracellular transport and signaling—hallmark activities of eukaryotic cells. The Lokiarcheotan genes are clearly related to eukaryotic genes, indicating a common origin.

Bacteria-within-bacteria is not only not a crazy idea, it probably accounts for the origin of Eucarya, and thus our own species.

We don’t know how common this arrangement is—we mostly study bacteria these days by sequencing their DNA. This is great for detecting uncultivatable species (which are 99 percent of them), but doesn’t tell us whether they are free-living or are some kind of symbiont. For that, someone would have to spend a lot of time prepping environmental samples for close examination by microscopic methods, a tedious project indeed. But one well worth doing, as it may shed more light on the history of life—which is often a history of conflict turned to cooperation. That’s a story which never gets old or stale.

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

Why Are We So Scared of Clowns?

Warner Bros.
Warner Bros.

With the recent box office-smashing success of Stephen King's It, it’s safe to say that coulrophobia (fear of clowns) isn’t a fringe phenomenon. The colorful circus performers are right up there with vampires and werewolves on the list of iconic horror villains. But unlike other movie monsters, clowns were originally meant to make kids laugh, not hide under their beds in terror. So what is it about clowns that taps into our deepest fears?

According to Yale doctoral candidate Danielle Bainbridge, the unsettling clown stereotype goes back centuries. In the inaugural episode of the PBS digital series Origin of Everything, Bainbridge explained the long history of this pervasive part of our culture.

Before clowns wore floppy shoes and threw pies at each other’s faces, early versions of the performers could be found in royal courts. The court jester wasn’t evil, but he was the only person in the kingdom who could poke fun at the monarch without fear of (literally) losing his head. The fact that fools didn’t fall within the normal social hierarchy may have contributed to the future role clowns would play as untrustworthy outsiders.

From the medieval era, clowns evolved into the harlequins of 16th-century Italian theater. Again, these weren’t bloodthirsty monsters, but they weren’t exactly kid-friendly either. The characters were often mischievous and morally bankrupt, and their strange costumes and masks only added to the creepy vibes they gave off.

Fast-forward to the 19th century, when the white-faced circus clowns we know today started gaining popularity. Unlike the jesters and harlequins that came before them, these clowns performed primarily for children and maintained a wholesome image. But as pop culture in the 1970s, '80s, and '90s showed us, that old perception we had of clowns as nefarious troublemakers never really went away. Steven King’s It, the cult classic Killer Clowns From Outer Space (1988), and that scene from Poltergeist (1982) all combined these original fears with the more modern association of clowns with children. That formula gave us one of the most frightening figures in horror media today.

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Why Do We Call a Leg Cramp a Charley Horse?

iStock.com/Jan-Otto
iStock.com/Jan-Otto

If you’re unlucky enough to have experienced a charley horse—a painful muscle spasm or cramp in your leg—then you may have found yourself wondering what this nonsensical phrase even means. Who is this Charley character? Where did he come from? And what does he know about my pain?

Like the words flaky and jazz, this term likely entered the language from the baseball field. While the idiom’s etymology isn’t 100 percent certain, archived newspaper articles suggest it was coined by a baseball player in the 1880s. We just don’t know which player said it first, or why.

According to a January 1887 article in the Democrat and Chronicle, the phrase was well-known to baseball players at the time—but to the average person, charley horses were as enigmatic as “an Egyptian hieroglyphic.” That year, charley horses were mentioned in a slew of newspapers across America, and some attempted to tackle the phrase’s murky origin. “Nearly every sporting journal gives a different version as to how the term charley horse originated in baseball circles,” the Oakland Daily Evening Tribune reported at the time.

The likeliest tale, according to the paper, centered around John Wesley "Jack" Glasscock, a shortstop who at the time was playing for Indianapolis. At some point a few years earlier, the player had strained a tendon in his thigh during a game and afterwards went home to his farm, where his father looked after a lame old horse called a "Charley horse." When the senior Glasscock saw his son limping along, he reportedly exclaimed, “Why, John, my boy, what is the matter; you go just like the old Charley horse?” John supposedly shared the funny turn of phrase with his teammates, and from there it spread. Similar accounts were reported in other newspapers, but they were attributed to various other players.

Other reports say the phrase has nothing to do with a live animal, but rather the fact that an injured player, while running, resembles a rocking horse or a child riding astride a wooden hobby horse.

The New Dickson Baseball Dictionary by Paul Dickson details a few other theories. In two versions of the same basic tale, Orioles or Chicago Cubs players went to the races and bet on a horse named Charlie who "pulled up lame in the final stretch." The next day, a player pulled a tendon in his leg and was said to resemble “our old Charlie horse.”

Alternatively, its origin may relate to an old workhorse that was tasked with pulling a roller across the infield. “Often in the 1800s, old workhorses kept on the grounds of ballparks were called Charley. The movements of the injured, stiff-legged ballplayers were likened to the labored plodding of these old horses, and the injury itself eventually became known as a ‘charley’ or ‘charley horse,'" Tim Considine wrote in 1982's The Language of Sport.

It also appears that charley horse originally implied a much more serious injury—or perhaps there was a bit of hysteria surrounding a condition that seemed new and scary in the late 19th century. The Democrat and Chronicle described a charley horse as a “giving way of one of the small tendons of the leg” and said an injured baseball player might need an entire season to recover. Another article from 1887 said ballplayer George Van Haltren’s relatives were worried he would get a charley horse, “although they do not know what that is.” He was said to have been “very fortunate” because he had “not yet encountered the terrible charley horse.”

For comparison, Healthline.com now says charley horses “are generally treatable at home” by stretching, massaging, or icing the afflicted area, although the muscle pain can linger for up to a day in some cases. So there you have it. We may never know the exact etymology of the charley horse, but the next time you get a sharp pain in your leg, you can thank an old-timey ballplayer for making your struggle sound so silly.

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