No s**t?!?! Interesting facts about poop

I was talking to my sister and four-year-old nephew the other day and my sister prompted him to tell me what he wanted to study when he grew up. He looks right at me and answers “poop”. Totally funny coming from the boy who really is obsessed with his own poop, but as a scientist, I responded that I could tell him lots about poop and asked, “what about poop are you interesting in studying?”  His response, “All of it.” Well, I agree. Poop is far more interesting than we give it credit for.  In the next two posts, I will share with you all the interesting stuff I know about poop.  This post will be facts about poop and the second post will be about using poop as a cure for diseases.  Let’s get down and dirty...

fecalmatterI’m not one of those people fascinated by poop.  I have never read any of the most popular books on the topic “Everyone Poops” or “What’s Your Poo Telling You“. In fact, I won’t even admit that I poop myself (as my husband will attest I insist that it’s all butterflies and rainbows down there).  But (butt!) being in a lab makes you think about things you never expected.  A common laboratory activity is something called a journal club. Held weekly, undergrads, graduate students and post-docs take turns discussing a scientific topic or journal article.  I like talking about the newest technology and controversial topics, so when it was my turn, I decided to look into the ancient, but recently rediscovered, therapeutic uses of poop to help cure diseases. As a started my research on the topic, I realized that I knew very little about poop in general.  Being the scientist that I am, I went to learn more.  And lucky you, I’m going to share!

watering_poopFirst and foremost, what is poop made of? The majority (75%) is water! The remaining 25% is a mix.  About a third of this 25% (doing the math, that’s 7.5% of your poop) is dead bacteria (back to that later) and a third fiber and undigested food (like those corn kernels you didn’t chew before swallowing).  The final third contains living bacteria, protein, cell linings, fats, salts, and substances released from the intestines and liver. In fact, the brown color of poop comes from some of these secreted substances such as bile and also bilirubin, which comes from dead red blood cells.

seven types of poopThere are seven different types of poop that have been categorized in the Bristol Stool Form Scale (or BSF for short) developed by Dr. Ken Heaton from University of Bristol.  I was going to spend the next 5 minutes wondering exactly what sort of methodology brought him to discover this seven type system, but then I just looked at the original article. “Sixty-six volunteers had their whole-gut transit time (WGTT) measured with radiopaque marker pellets and their stools weighed, and they kept a diary of their stool form on a 7-point scale and of their defecatory frequency.” I’m glad I was not a volunteer in that study – keeping a daily diary of my stool form and have the length of time from mouth to poop tracked – ick!  However, Dr. Heaton was able to conclude that the form the stool takes depends on the time it spends in the colon, with 3 and 4 being ideal stools. Now one more thing for siblings, partners, and spouses to argue about – who’s poo is better?

But(t) let’s get serious.  Besides being an indication of intestinal health, poop is also filled with bacteria.  These bacteria are representative of the bacteria that can be found in your gut and are part of your “microbiome“. Your microbiome (all of the bacteria and other bugs in and around your body) outnumber your human cells 10 to 1, and scientists think that 300-1000 bacterial species inhabit the GI tract alone!  We’re not entirely sure exactly how many species because most of these bacteria don’t grow outside the gut (in the presence of oxygen), and when we look for gut bacteria by sequencing the DNA of poop samples, we’re not sure if the bacteria in poop represents all the bacteria that are found in the gut.

Either way, what do all those bacteria do? They help with digesting food and producing vitamins.  They regulate fat storage and do some crazy things like influence the immune system and the brain (more on that in a future post).  These bacteria are also protective against pathogens, like bad  infectious bacteria or viruses. How the gut microbiome protects against pathogens is still being studied, but we know that some gut microbiome bacteria create antimicrobials that kill bad bacteria.  In other cases, its all about the balance of the good bacteria versus the bad.  When this balance changes, it can be a cause or consequence of the disease. And one of the cures to these diseases, might just be poop itself, which is what I’ll discuss in my next post.

Want to learn more about poop?  Check out some of these resources:

What does DNA look like? Like, really?

Everyone talks about DNA.  And shows those lovely double helix cartoon images of DNA. But when you’re a researcher in a lab, what does DNA actually look like?  How in the world do we see it?


  1. X-Ray crystallography.  To be fair, this is an indirect way to see DNA but it is the way that the structure of DNA was determined (as described in our book club book The Double Helix) so it’s worth mentioning.  Remember when you were a kid and you made rock candy by hanging a string or stick in water that had a ton of sugar dissolved into it?  Well scientists can do the same thing with DNA or proteins – make crystals of them.  These crystals are much smaller than the crystals in rock candy.  Think microscopic.  When molecules are all lined up in the same direction, like they are when they form a crystal, scientists can hit the crystal with X-rays and what bounces around and through the crystal can be detected (this is called a diffraction pattern), measured and transformed to determine the 3D image of the molecule – that double helix structure you see pictures of all the time.  This process is called X-Ray crystallography and for the first images of DNA, the diffraction pattern looked like the picture to the left.
  2. dna_in_cellMost scientists do not look at DNA to the atomic level like in X-Ray crystallography, but rather want to see it inside of a cell. The DNA in a cell is inside the nucleus and certain dyes (such as the Hoechst dye) bind to DNA.  Under UV light, the Hoechst dye glows, showing exactly where the DNA is in the cell.  If you look at the picture to the right, you can see the outline of three cells and the blue DNA inside the nucleus of those three cells. Why would a scientist want to see where the DNA is and what it looks like? You can learn a lot from just looking at the DNA. For example, whether or not a cell is dividing or dying, which can be really important if you want to know whether or not the cancer cells you are studying die when you treat them with a drug.
  3. Scientists don’t always look at the DNA directly inside of a cell either.  For an experiment they may want to isolate the DNA (meaning, take the DNA out of a lot of cells to dna_in_eppendorfstudy it) and then manipulate it in some way (sequence it, amplify it, modify it, etc).  Once my mom asked me how big DNA is when you take it out of cells and work with it in the lab.  Well, the answer is that you need a LOT of it to even see it.  In the lab, we may grow bacteria in 5 ml of growth media, which after growing overnight contains 10,000,000,000 cells.  We then bust these cells open with a detergent (like soap, but not soap), spin out all of the extra bits of cells, and then force the DNA to show itself by adding an alcohol like ethanol in a process called precipitation (if you want to learn more about the details, check out this article).  How much DNA do you get in the end – well it depends, but it’s not a lot, visually at least.  And what does it look like?  See the whitish smear at the bottom of that tiny tube?  That’s the DNA.

Are there other ways to see DNA?  YES!  But many of them are based on dyes like the one described in #2 above.  At some point, we’ll definitely talk about them in the context of analyzing DNA sequence and running gels.  And I’m not talking at all here about “seeing” DNA by determining it’s sequence, even though that’s important too.

strawberry_dnaSo now that you know a few ways that scientists see DNA, it’s your turn.  Grab a lab partner, and isolate DNA on your own!!  Don’t know how?  No problem!  There are a number of different ways to isolate DNA at home, the most common being from the cells of an onion or the cells of strawberries.  The experiments for extracting DNA from ONIONS or STRAWBERRIES are linked. At the end of the experiment, what will you see?  Long strands of isolated DNA from all of the onion or strawberry cells. Enjoy and please share photos and stories of your DNA isolation adventures!