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.)

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.

Amazon's Under-the-Radar Coupon Page Features Deals on Home Goods, Electronics, and Groceries

Stock Catalog, Flickr // CC BY 2.0
Stock Catalog, Flickr // CC BY 2.0

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

Now that Prime Day is over, and with Black Friday and Cyber Monday still a few weeks away, online deals may seem harder to come by. And while it can be a hassle to scour the internet for promo codes, buy-one-get-one deals, and flash sales, Amazon actually has an extensive coupon page you might not know about that features deals to look through every day.

As pointed out by People, the coupon page breaks deals down by categories, like electronics, home & kitchen, and groceries (the coupons even work with SNAP benefits). Since most of the deals revolve around the essentials, it's easy to stock up on items like Cottonelle toilet paper, Tide Pods, Cascade dishwasher detergent, and a 50 pack of surgical masks whenever you're running low.

But the low prices don't just stop at necessities. If you’re looking for the best deal on headphones, all you have to do is go to the electronics coupon page and it will bring up a deal on these COWIN E7 PRO noise-canceling headphones, which are now $80, thanks to a $10 coupon you could have missed.

Alternatively, if you are looking for deals on specific brands, you can search for their coupons from the page. So if you've had your eye on the Homall S-Racer gaming chair, you’ll find there's currently a coupon that saves you 5 percent, thanks to a simple search.

To discover all the deals you have been missing out on, head over to the Amazon Coupons page.

Sign Up Today: Get exclusive deals, product news, reviews, and more with the Mental Floss Smart Shopping newsletter!

Why Does the Supreme Court Have Nine Justices?

Front row, left to right: Stephen G. Breyer, Clarence Thomas, (Chief Justice) John G. Roberts, Jr., Ruth Bader Ginsburg, Samuel A. Alito. Back row: Neil M. Gorsuch, Sonia Sotomayor, Elena Kagan, Brett M. Kavanaugh.
Front row, left to right: Stephen G. Breyer, Clarence Thomas, (Chief Justice) John G. Roberts, Jr., Ruth Bader Ginsburg, Samuel A. Alito. Back row: Neil M. Gorsuch, Sonia Sotomayor, Elena Kagan, Brett M. Kavanaugh.
Fred Schilling, Collection of the Supreme Court of the United States // Public Domain

Some facets of the U.S. government—like presidential terms and post offices—were written into the original Constitution after (often lengthy) deliberations by the Founding Fathers. The number of Supreme Court justices was not one of those things.

The document did establish a Supreme Court, and it stated that the president should appoint its judges; it also mentioned that a “Chief Justice shall preside” if the president gets impeached. Since it was left up to Congress to work out the rest of the details, they passed the Judiciary Act of 1789, which outlined an entire court system and declared that the Supreme Court should comprise one chief justice and five associate justices. As History.com explains, they landed on six because the justices would have to preside over federal circuit courts, one of which was located in each state. Traveling wasn’t quick or easy in the horse-and-carriage days, so Congress wanted to minimize each justice’s jurisdiction. They split the courts into three regions, and assigned two justices to each region.

According to Maeva Marcus, director of the Institute for Constitutional History at George Washington University Law School, the even number of justices was a non-issue. “They never even thought about it, because all the judges were Federalists and they didn’t foresee great disagreement,” she told History.com. “Plus, you didn’t always have all six justices appearing at the Supreme Court for health and travel reasons.”

Over the next 80 years, the number of Supreme Court justices would fluctuate for two reasons: the addition of federal circuit courts, and presidents’ partisan motives. John Adams and his Federalist Congress reduced the number to five with the Judiciary Act of 1801, which they hoped would prevent Democratic-Republican Thomas Jefferson from getting to fill a seat after he took office that year. By the following year, Jefferson’s Congress had passed another judicial act that returned the number of justices to six, and they upped it to seven after forming another circuit court in 1807.

The nation grew significantly during the early 19th century, and Congress finally added two new circuit courts—and with them, two new Supreme Court seats—during Andrew Jackson’s presidential tenure in 1837. Republican Abraham Lincoln then briefly increased the number of justices to 10 in order to add another abolitionist vote, but Congress shrunk it to seven in 1866 to keep Andrew Johnson from filling seats with Democrats. As soon as Republican Ulysses S. Grant succeeded Johnson, Congress set the number back to nine, where it’s remained ever since.

Sketched portraits of the U.S. Supreme Court justices through 1897.Popular and Applied Graphic Art Print Filing Series, Library of Congress Prints and Photographs Division // No Known Restrictions on Publication

In 1911, Congress did away with circuit courts altogether, so the number of Supreme Court justices stopped being contingent upon their expansion (though each justice does still oversee a region to help with occasional tasks). As for presidents shifting the number to serve their own goals, it’s now looked down upon as “packing the court.” When Franklin D. Roosevelt tried to increase it to 15 in the 1930s to push his New Deal through the Supreme Court, the Senate opposed the bill by a whopping 70 to 20 votes.

In short, the depth of the Supreme Court’s bench changed a lot in America’s early years not only because the country was expanding, but also because the federal government was still testing out its system of checks and balances. And though presidents do still appoint justices based on their own political party, we’ve gotten used to the idea that the Supreme Court is, at least ideologically, supposed to be unbiased. If Congress and the president kept up the habit of adding and subtracting justices at will, it would tarnish this ideal.

“If Congress increases the size of the Supreme Court for transparently partisan political reasons, it would cement the idea the justices are little more than politicians in robes, and that the court is little more than an additional—and very powerful—arm through which partisan political power can be exercised,” Steve Vladeck, a professor at the University of Texas School of Law, wrote for NBC News. “Indeed, that Congress has not revisited the size of the court in 150 years is a powerful testament to just how ingrained the norm of nine has become—and how concerned different political constituencies have been at different times about preserving the court’s power.”

[h/t History.com]