You Keep Me Hangin’ On – What Makes Your Gut Bacteria Stick Around?

Why moving your bowels doesn’t move most of your bacteria.

I wonder…

Do you take a look at what you’re about to send on its way to the sewer, before you flush?

I’m not sure what the collective noun for a group of gastroenterologists is (a gutful?) but a team of British specialists in this area wanted a definitive answer to how many do, and how many don’t.

They came up with the, perhaps surprising, result that only around one-in-four examined both stool and toilet paper every time.

Maybe even more remarkably, 102 of their 1,611 participants (6%) never examined either.


If you are a poop-peeper, however, you’ll almost certainly have noticed undigested food lurking in the logs from time to time.

The worst offenders are corn, peanuts, carrots, and beans, and what you’re spotting is high-fiber vegetable matter your gut couldn’t process.

According to an expert at the Mayo Clinic, there’s nothing to be alarmed about when this happens occasionally.

But given that some food is able to pass through the winding 30-foot length of your gastrointestinal tract pretty intact, you may be forgiven for wondering why bacterial cells, or at least some of them, are able to go in and stay in.

What makes bacteria stick around in your gut?

Well, if you’ve ever picked an object out of a pond and found it slippery, that’s almost certainly because bacteria and other microorganisms such as eukaryotic algae have formed what’s known as a biofilm on its surface.

This slimy, but surprisingly durable, coating is formed when bacterial cells have colonized (multiplied) and “stuck” to a surface.

In order to explore this effect, scientists at Princeton University placed E. coli bacteria into vials containing small glass beads.

When the bacteria adhered to the beads, the researchers determined that the cells had been able to sense the surface, activating protein-encoding genes that turned on something called a Cpx pathway.

When you examine bacteria under a powerful microscope, you’ll spot that many species have what looks like hairy bodies.

A single cell can have as many as 1,000 of these “hairs” or—more technically—fimbriae or pili.

(Pilus is the Latin word for hair.)

In many cases, it’s the very tips of these fimbriae that enable a bacterium to fasten itself to a surface, due to a small protein subunit.

These kinds of “biological glues” are known as bacterial adhesins, but intriguingly adhesins are very picky about what they stick to.

Certain bacteria adhere to certain surfaces, and not others.

In a 2012 paper, scientists at the University of Groningen in The Netherlands helpfully observed that “adhesion to a surface is a survival mechanism for bacteria.”

I know we’re mainly focused on the gut right now, but it’s easy to understand microbes’ need for adhesion when you think about the oral microbiome.

Bacteria can easily form a biofilm on teeth and gums, but any cells that don’t stick get swallowed and consigned to an almost certain death as they pass into the harshly acidic conditions of the stomach.

Microbiologists refer to bacterial adhesins as “virulence factors” because it’s by adhering to a surface in or on a host that pathogenic (disease-causing) cells can exhibit harmfulness, by assisting and promoting colonization.

When it comes to pathogenic bacteria, there’s definitely strength in numbers.

Research has shown that bacteria in biofilms are from 10 to 10,000 times more resistant to antibiotics than free-floating bacteria, which are often referred to as “planktonic”.

Planktonic bacteria don’t hang around that long, so it’s largely the adhering kind that makes up your microbiota.

The inside of your gut consists of a type of mucus-coated tissue called the epithelium, on whose surface bacteria cling, limpet-like, either helping or hindering your body’s health, according to their species.

The epithelium plays a crucial role in keeping pathogenic bacteria out of your bloodstream.

Its integrity provides a vital barrier between microbes and your inner workings.

Biofilms can form on many kinds of surfaces, including on prosthetic replacements such as knee or hip joints, resulting in the body rejecting the addition, one good reason why it’s so important to avoid infection in surgery of this kind.

Finally, a reminder: bacteria’s stickiness makes it important to remember that proper dental hygiene means thorough brushing—not just to dislodge food particles, but also to knock those hairy little bugs off their perches before the biofilm begins to build up.

Further reading

A closer look yields new clues to why bacteria stick to things

Bacteria – Pili

Bacterial adhesin

Bacterial Interactions with the Host Epithelium

Do you look at your poo? If not, here’s why you should.

Epithelial-cell recognition of commensal bacteria and maintenance of immune homeostasis in the gut.

Factors associated with the frequency of stool examination.

Fimbria (bacteriology)

How Bacteria Stick

How Bacteria Stick Together

How Do Bacteria Know They Are on a Surface and Regulate Their Response to an Adhering State?

Sticky Situations – Key Components That Control Bacterial Surface

Understanding How Bacteria Adhere to Surfaces