Truth, the Internet, and the Number of Bacteria on Your Body

by Jan Thornhill

Before I started writing and illustrating kids' books, I did a weekly cartoon for Toronto's Now Magazine. I mined what I thought were entertaining factoids out of whatever I was reading or whoever I was listening to at the time, and illustrated these "truths" in scratchboard. I even called it, for a while, "True Stuff." 

Truth be told, I sometimes accepted as truth anecdotes told to me by other people, or things that came from dodgy sources such as supermarket tabloids. I admit, too, that I sometimes even made up some of what I drew. The above cartoon, however, was supposed to be one of the honest-to-gosh fact-based truths I'd come across and copied into my notebook. Perhaps you've heard or read something similar, something like "bacteria in the human body outnumber the body's own cells by 10:1."

Tasha Sturm, a college microbiology tech, got her young son to gently
press his hand on a petri dish full of agar after he had been outside.
This is the fabulous collection of bacteria that grew! (photo: Tasha Sturm)

When I first came across this "teacupful" tidbit back in 1985, without the luxury of having everything at my internet-connected fingertips like I do today (even in the woods, even in the middle of the night, even a hundred miles from the closest big city), my fact-finding abilities were heavily reliant on what I read in books, newspapers, and magazines. Back then, I had to trust what I read, mostly because it was so very difficult to question the veracity of the printed word. How, back then, if I had questioned the trustworthiness my source, would I have been able to verify if it was true? I mean, even if something like the above statement about "a teacupful" of bacteria was sourced from, say, a research paper in an obscure journal, how would I, a non-academic, have been able to access such a thing back then? 

A close-up of the large flower-shaped colony from the above photo
that is probably made up of several million bacteria (Tasha Sturm)

My point is that back then, in the olden days before the internet, I had an excuse to repeat things that were sometimes untrue. Or at least more of an excuse than I have now. (I also seemed to have a heck of a lot more spare time back then, precisely because I didn't have easy access to so many of the scientific papers I now read—but that's a different story.) 

Back to the number of microbes on and inside a human body. I would never have fished out this old cartoon if I hadn't recently come across the following headline (on the internet, of course!): "Scientists bust myth that our bodies have more bacteria than human cells."

Artist Rogan Brown's amazingly beautiful (and intricate!)
hand-cut paper sculpture of a bacterium  (Rogan Brown)

Here's the gist of what's come to light. This 10:1 bacteria-to-human-cell statistic, which gets almost nine thousand pre-2016 hits on Google, is based on a statement published in a review in 1977, a statement which had, in turn, been based on an earlier unsubstantiated calculation taken from a 1972 article. A group of researchers in Israel and Canada now say the ratio is more likely to be, on average, closer to one-to-one. Some people might have double that number of bacteria, some only half. And everyone loses almost their entire microbial load on a daily basis—at least they do if they're "regular," since the vast majority of human's bacteria reside in the colon. So the ten-to-one ratio is actually an academic urban legend.

But there's the rub: I haven't actually read the new study, nor have I read either the journal article or the review from the 1970s that I've cited in this post. Am I lazy, or is it reasonable for me to trust the distilled versions of the paper that have been published on the websites of the journal Nature, the National Geographic, and Scientific American, among others? I can't answer that. All I know is that it's getting harder and harder to figure out what is believable, not just on the internet, but also in contemporary books since so many are now based on internet research. I just hope I rehashed the gist of what I've been reading about the current research without garbling it too much—because I'm obviously as capable as anyone else of modifying what I've read when I rehash it.

Artist Elin Thomas uses felt and crochet to create petri
dishes packed with "moulds" and "bacteria." (Elin Thomas)

Take that original teacupful of bacteria "fact" I riffed off of all those years ago. Even with the mighty internet I cannot find a specific reference anywhere to "a teacupful" of bacteria on the human body. What I have found, though, are two separate references to the mass of all those trillions of bacteria found in humans equalling that of "a teacup Yorkie" or as being "roughly the same weight as a teacup chihuahua." Perhaps I was guilty way back then of dropping a qualifier in my copying down of this cool little factoid! 

More Academic Urban Legends:

If you think spinach is a rich source of iron, read this entertaining paper: 

Rekdal, Ole Bjørn. Academicurban legends, Social Studies ofScience August 2014 vol. 44 no. 4 638-654

Check out our very own Helaine Becker's UBC article that highlights an academic urban legend about how pearls are formed! And if you happen to meet Helaine, ask her about Mendel's Peas.

More Information:

Directions for making a bacteria handprint in agar are contained in the Comments section of Tasha Sturm's original post on Microbeworld.org (N.B. Once the plates are grown they should NEVER be opened!!!!! The colonies on the plate can represent millions of bacteria that could potentially make someone sick. Mold also contains spores that could be inhaled causing serious problems as well.)

Rogan Brown's website with more dazzling cut-paper microbe art

Rogan discusses his science-based art in a short video

More of Elin Thomas's work on Flickr and on Etsy 

And if you want to know all about microbes and the human body, pre-order Inside Your Insides: A Guide to the Microbes That Call You Home, the latest book written by Sci/Why's own Claire Eamer (illustrated by Marie-Eve Tremblay)!

References

Scientists bust myth that our bodies have more bacteria than human cells on Nature.com

Ron Sender, Shai Fuchs, Ron Milo. Are We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host Cells in Humans. Cell, 2016; 164 (3): 337

Make Mine Maple

by Helen Mason

At the first signs of spring, when the days get longer, the snow begins to melt from around the roots of the maple trees, and the temperatures rise to slightly above freezing during the day but stay cold at night, the sweet sap in the maple trees begins to flow. That's when both professionals and hobbyists tap sugar maples for sweet sap that is boiled until most of the water has evaporated. What's left is an amber-coloured liquid called maple syrup.

Sugar bush in early spring

The sugar in this sap was produced the previous year when sunlight, reacting with the chlorophyll of the leaves in sugar maples, produced sugar. This sugar was stored in the tree and released when the spring warmth caused the sap to rise from the winter-frozen roots.

Sugar maple trees are unique to eastern North America. Their sweet sap was first harvested by Aboriginal tribes during the "maple moon."

French and English explorers wrote of the "sweet water" that North American Indians took from the trees and boiled down to a coarse dark brown sugar. In the 18th and 19th centuries maple sugar was an important food item and was used for trading. By the late 19th century, however, white cane sugar, which was cheaper and easier to get, replaced maple sugar as the sweetener.

This hobby bush is in a sugar maple stand near Parry Sound, ON.

Today, maple syrup and sugar are made both by hobbyists and professionals. Commercial bushes use pipeline to move the spring sap to an evaporating shed where it is boiled in large commercial evaporators. Many hobbyists tap a small number of trees and make just enough syrup for their family and friends.

In 1980, Mark Mason used a battery-powered drill to tap.

In small bushes, the process begins when the hobbyist drills a hole in the tree trunk to collect some of the sap as it rises. A cone-shaped funnel or "spile" is hammered into each tap and a bucket hung from the hook attached to each spile. As each day warms, sap plinks into the buckets, creating a springtime maple melody.

In most bushes, the sap is collected and poured into a large flat evaporating pan. The sap is boiled until the watery liquid gradually turns from pale yellow through gold, to a warm amber. This process uses up a lot of firewood, gas, or propane. In some commercial bushes, it's sped up by reverse osmosis.

Partially boiled sap is poured into a hydrometer cup. Is it maple syrup yet?

The work demands patience. About forty litres of sap produce only one litre of maple syrup. Making it demands hours of boiling, buckets of patience, and many maple trees.

As the temperature of the boiling sap begins to rise, the specific gravity is checked. The finished product has a specific gravity of 1.37 and boils at exactly 104 °C. Traditionalists use a glass column called a hydrometer that will show about two-thirds of its length when the correct specific gravity has been reached.

A felt sock filter purifies some dark syrup from late in the season.

Once the syrup reaches this stage, it's quickly removed from heat, filtered to remove any impurities, and bottled or canned, ready for you to enjoy over pancakes or in your favourite maple recipe.

Animals Have Cultures, Too

by L. E. Carmichael

Behaviour is what you do, culture is how you do it.

This is totally obvious in human cultures, which have rules and guidelines for every behaviour - from table manners to what we wear to how we greet each other. But in the last few decades, scientists have begun to realize that animals have culture, too.

And we're not just talking about primates.

A recent National Geographic's Weird Animal Question of the Week deals with accents and dialects in animal communication. One of their examples is wild canines, whose howls are not only distinctive between species - grey wolves and coyotes - but are also characteristic to particular geographic regions and populations. These differences probably help animals identify members, not just of their own family groups, but of their broader regions.

The article mentions the long, single pitch howl of the arctic wolf, a group I studied during my PhD research on the genetics of wolves and arctic foxes. My work focused on gene flow, the transfer of genetic material from one population to another. For gene flow to occur, an animal must do two things:

1) Leave the population it was born in

2) Find a mate in a new geographic region, thus passing its genetic material into the next generation.

I discovered there was very little gene flow between tundra wolves and wolves living below the tree line, even though there were no physical impediments to travel between the areas. More surprising, there were several distinctive populations of wolves on the tundra, signalling low gene flow even among wolves living in what was apparently the same habitat.

Or was it?

What I'd stumbled on turned out to be another signal of animal culture - hunting behaviour. All wolves hunt, but what they hunt varies. It has to, because different prey species prefer different habitats. Wolves below Canada's tree line, for example, eat deer and moose - animals that tend not to move around much. Wolves in the tundra mostly eat barren ground caribou - animals famous for their long-distance migrations. And wolves in the tundra were sorting themselves into populations that corresponded with the migration ranges of their prey.

What this suggests is that wolves are doing more than passing distinctive dialects down to their young. They are teaching their pups how to hunt particular food types. And once the pups learn effective hunting strategies, they tend to stay in an area where they can use those strategies. Because tundra wolves are most often mating with other tundra wolves, their genes as well as their behaviour will diverge from those of wolves in other areas.

Culture - one more thing that does NOT separate humans from animals. :)

Interested in learning more about animal communication? Check out Fox Talk: How Some Very Special Animals Helped Scientists Understand Communication.

Eclipse Plans

NASA has plans for the total eclipse of the sun expected in Indonesia on March 9. Here's their short video discussing the photographs they plan to take during that brief time:

 

If the video doesn't load here, you can see it by clicking on this link. Click on it anyways if you're interested in eclipses! On that webpage, NASA writers have posted several short comments with interesting pictures on their studies of eclipses and the sun. Most important among these comments is the advice on eye safety when observing a solar eclipse -- that's a must read for anyone!

The Importance of “Thoughtful Spots”

By Melissa Stewart, guest blogger

“Half way between Pooh’s house and Piglet’s house was a Thoughtful Spot where they met sometimes when they had decided to go out and see each other . . .”
         —The House at Pooh Corner by A.A. Milne

I think everyone should have a Thoughtful Spot—a quiet place in nature where they can be alone with their thoughts. And for writers, I think a Thoughtful Spot is absolutely essential. My guess is that beloved author A.A. Milne felt exactly the same way.

Today more than ever before, daily life is busy and chaotic. We need time and space to analyze and process and evaluate it all. Only then, can our minds be free to dream and imagine and find the inspiration the fuels us.

My Thoughtful Spot is a pond about 20 minutes from my home.


While walking along the wooded trail surrounding the pond, I’ve solved many problems that seemed insurmountable while sitting at my keyboard, staring a mess-of-a-manuscript.

This same special spot provided experiences and observations that led directly to two of my most popular books—Under the Snow and When Rain Falls. I take you to the pond and describe those book-generating experiences in a video called Where Do Ideas Come From.

Do you have your own Thoughtful Spot? I hope so. Visit it often and soak up its treasures.

And it you don’t, I heartily encourage you to make time to explore some natural areas near your home. My guess is that it won’t take long to find a special place where you can go to slow down and reconnect with the part of yourself that’s open to all the possibilities the world has to offer.

Why not give it a try? After all, it worked for Winnie-the-Pooh.

Melissa Stewart is the award-winning author of more than 150 nonfiction books for children, including No Monkeys, No Chocolate; Feathers: Not Just for Flying; Under the Snow; and Animal Grossapedia. She maintains the blog Celebrate Science and serves on the board of advisors for the Society of Children’s Book Writers and Illustrators.

(P.S. For anyone wondering why an American writer is guesting on a Canadian kids' science writers' blog - we just like her work! - CE)

Why I Love Twitter

By Claire Eamer

I confess - I absolutely love Twitter. And it's not because I'm a social media geek. It's because of the science. Really!

I know Twitter has a reputation as the place where you post the boring minutiae of your life (and how many times do you get to use "minutiae" in conversation, eh?). But Twitter is actually the place where I find the coolest science stories.

I've found stories so unexpected that I'd never think to search for them. Or breaking stories. Or stories that are simply too cool for school! Of course, the best stories of all are the ones that are totally cool enough for school.

For example, who knew there are deviant corals? And that it's a good thing? I certainly didn't!

What makes a "Deviant Coral" survive a mega-El Niño? Post by @ClaarDanielle on @baumlab's new blog. Great read! https://t.co/OcLU3q7SLh

— realscientists (@realscientists) February 11, 2016

Or that bacteria have eyes. Or are eyes. Or can see. Sort of...

This bacterium acts like a one-cell eyeball https://t.co/dKrrgYcxnX pic.twitter.com/twQkjNi9gB

— The Atlantic (@TheAtlantic) February 9, 2016

And then there's this week's breaking science story - about gravitational waves. Mind boggled by that one? If you want to follow the story or understand it, the Twitterverse has got you covered:

"Biggest Scientific Event of the Decade" #gravitywaves Discovered! Watch the Video: https://t.co/S89Cgvn05X pic.twitter.com/56IHt7FykU

— Check123 (@check123com) February 12, 2016

And then there are the regular Twitter users I follow for the great science stories they tell. Science writer Ed Yong, for example. Or Brian Switek, who loves dinosaurs with a passion equalled only by the nearest five-year-old. Or Sarah Boon, who thinks and writes very well about both science and science communication.

If you want to learn what's happening in Canadian science, check out the feed from Science Borealis. Here's an example:

New post #fromthefeed Life amid acidity near a smoldering part of the Arctic https://t.co/LOhniPEXld

— Science Borealis (@ScienceBorealis) February 11, 2016

You can even find a bunch of the Sci/Why crew on Twitter: Helaine Becker, Paula Johanson, Lindsey Carmichael, Joan Marie Galat, Marie Powell, occasional blogger Margriet Ruurs, and even me.

And here's one final, awesome tweet:

Listen to this!
Caribbean Whales Have an Accent: https://t.co/Dft3cjQUv5 #marinemammals #zoology pic.twitter.com/TiP8mrleaT

— Hakai Magazine (@hakaimagazine) February 12, 2016

Enjoy!

The Scoop on Sloth Poop

By Jan Thornhill

Illustration from Kyle Goes Alone (Illustration: Ashley Barron)

I didn't plan to write a book about pooping sloths—honest, I didn't. What I planned was to write a fairly straight-forward information book about the myriad forms of life that call a rainforest tree "home." I started, as usual, by simply gathering information about likely candidates that I could focus on: snakes; frogs; birds; vines and lianas; insects; fungi; bromeliads and other aerial plants; and, of course, mammals. It was all coming together nicely...but then I hit on sloths.

(Fernando Flores, Wikipedia)

I've always liked sloths, those sleepy-eyed characters that hang upside with goofy grins on their faces, moving unbelievably slowly or not moving at all. I actually emulated sloths in my teens, at least that's what my parents suggested, though they usually just used the word "lazy."  

(J.C.D. Schreber, Die Säugthiere in
Abbildungen nach der Natur, 1855)*

So I started reading about sloths and it wasn't long before I came across the kind of startlingly wonderful information that makes my heart sing: sloths only poop once a week. And why do they only poop once a week? Because sloths really are slow. In fact, not only are they so slow-moving that researchers' motion sensing cameras are sometimes not triggered when they pass, their digestive processes are the slowest of any mammal.

(Charles Dessalines d'Orbigny, 1849)*

Sloths primarily eat leaves. Tree leaves, particularly thick, long-lasting tropical tree leaves, are not packed with nutrients, nor are they easy to digest since their cell walls are made up of cellulose and lignin—just like a tree's wood, bark and branches. The only way a sloth can digest this tough stuff is with the help of gut bacteria, and this process takes a long time—a single leaf can take a month to travel from one end of a sloth to the other! 

(J.C.D. Schreber, Die Säugthiere in
Abbildungen nach der Natur, 1855)*

I also learned that some sloths add another fascinating bit of behaviour to this slow digestion. Three-toed sloths only poop on the ground, despite the ground being an unbelievably dangerous place to spend time for a creature whose hanging-upsidedown-from-trees anatomy is ill-suited to walking—more than half of all sloth deaths are caused by predation during these weekly excursions. 

(1776)*

And then I found this video of baby sloths being "potty trained" at a sloth rescue centre in Costa Rica—just about the cutest thing I've ever seen. And suddenly I wasn't working on the book I thought I was working on anymore. Now I was writing a picture book called Kyle Goes Alone (Owlkids Books, illustrated by the brilliant Ashley Barron), the story of a young sloth's first trip to the ground alone, cheered on by camouflaged rainforest neighbours. I managed to work much of the above sloth poop information into the book, but I didn't have room for the following, even more entertaining information. 

Two-toed sloth (Albertus Seba, 18th Century)*

Three-toed sloths carry their very own ecosystems in their fur coats. Their hair is grooved, and in the humid rainforests where they live, these grooves are a perfect place for algae to grow, algae that can be plentiful enough in the rainy season that a sloth can appear to be completely green—not a bad colour if you live amongst green leaves. Along with algae, sloth hair also harbours all kinds of fungi, ticks, mites, and insects. Some of the insects are moths that, as adults, live nowhere else other than between the hairs of a sloth's thick coat. Their other life stages—egg, larva, and pupa—are all spent in...drum roll, please...sloth poop.

(Frederick P. Nodder, 1789)*

Here's how this works: The adult moths, which have no mandibles, so likely don't eat, hang around on a sloth, seeking out another moth of the opposite sex. Then they do what they're supposed to do, which is procreate. Pregnant females wait until that happy moment when the sloth's weekly urge to "go" drives it slowly down to the ground. Once on the forest floor, the sloth, which often carries around a third of its body weight in waste (imagine!!), uses its tail to carve a little hollow in the ground, then defecates. This is, of course, the moment the female moths are waiting for. They crawl out of the sloth's hair and flutter down to the hard pellets where they lay their eggs. Once the eggs hatch, the larvae have ample food, particularly since they have the advantage of having arrived before any other forest dung-eaters. They eat to their hearts' content and then pupate. When an adult emerges, it flies upwards to search out some sloth fur to take up residence and seek out a potential mate—a sloth that is likely to be the same one its parents lived on since these animals are very fond of certain trees and don't stray far from them.

(1889)

So what do three-toed sloths get out of this relationship? No one yet knows, but one possibility is that the moths somehow fertilize the algae that grows in the fur, which the sloths in turn might eat to supplement their otherwise poor diets. Unfortunately, no one has observed sloths eating algae from their coats, but it's possible they might do this as night when they are notoriously difficult to observe. 

(Maximilian Wied, Abbildungen zur
Naturgeschichte Brasiliens, 1822)

Other researchers are unconvinced that there is a symbiotic relationship between the moths and the sloths. They think that the sloths' habit of pooping on the ground at the base of their favourite tree is more about communication and procreation with other sloths, especially since a female in oestrus will go down to the ground every day. If this is true, the moths might just be opportunistically hitching rides on sloths so they can be "delivered" to the poop their offspring need to survive. 

(Ashley Barron)

Kyle Goes Alone (written by Jan Thornhill, illustrated by Ashley Barron), Owlkids Books, 2015

Baby Sloths get Potty Trained Video



*Many early animal illustrators never saw the animals they depicted, hence some pretty fabulous sloth pictures!