Role of Bacteria in Gastrointestinal Health

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Besides food, do you know what else is found aplenty in your gut? Bacteria! Find out how many, where and what types as we go over the role of bacteria in gastrointestinal health. Updated: 06/16/2021

Bacteria in the Gut

You are more microbacterial than you think. What that means is that your body is made up of something along the lines of 30 trillion cells. But your gut, the intestines, contain upwards of 100 trillion microorganisms, namely bacteria. So, in the numerical count of cells in and of your body, you are more bacteria than human if those estimates are to be believed.

Of course, that's an exaggeration of sorts but what isn't an exaggeration is the important role these bacteria play in gastrointestinal health. Let's find out how and why in this lesson.

Type & Location

In the gut, you have somewhere between 300-500 different species of bacteria. As you can understand, we can't possibly cover them all in a relatively short lesson. So, let's focus on naming a handful of examples of the types and locations of bacteria in the gastrointestinal system. We'll get to the general role of all of these bacteria in gastrointestinal health in the next section.

Your stomach and the first part of the intestinal tract, the one that hooks up immediately to the stomach, have relatively smaller numbers of bacteria in healthy people. Why? Well the stomach acid, alongside the biliary and pancreatic secretions, kill off many of the bacteria here. The types of bacteria found in the first portions of the gastrointestinal tract are mainly aerobic, oxygen-loving, in nature and largely come from your mouth and your throat as you swallow your food and saliva. Some bacteria you might find here include Streptococci and Helicobacter pylori.

In later segments of the intestinal tract, namely the colon, anaerobic bacteria predominate. These are bacteria that aren't so keen on being around oxygen. The bacteria found in the colon include the likes of:

  • Bacteroides
  • Bifidobacterium
  • Lactobacillus

General Role of Bacteria

So what are all of these bacteria doing here? Well, some are there to help us, the good bacteria. Others are bad bacteria, in that they may be present transiently to cause disease. Or, they may be there all of the time but don't cause us any issues until we're sick with something else. These are known as opportunistic bacteria.

Bacteria found near the mucosal surface of the intestinal tract are probably there to help us regulate our immune system. Bacteria found near the lumen, the open space where food and feces flow through, are likely involved in digestion.

Some of the bacteria in our intestinal tract help to keep us healthy by outcompeting the transient or opportunistic pathogens. For example, they may kill off these disease-causing organisms either directly or via competition. In other words, they'll try to outcompete the bad bacteria by taking up space or food the bad bacteria need to survive. Other good bacteria found in our intestinal tract may signal our immune system to activate biochemical and cellular defenses against pathogenic, disease-causing, bacteria. So, they act as lookouts of sorts for our gut and body! Pretty cool, right?

Specific Examples

Now that you've got the basic facts down, why don't we take a look at a couple concrete examples of how the good bacteria in our gut keep our intestinal tract healthy?

Some of the bacteria found in your intestinal tract have anti-inflammatory properties. One of these is known as Faecalibacterium prausnitzii. And you know what's interesting? This anti-inflammatory bacterium has been found in lower numbers in people with inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn's disease. IBD can cause a lot of pain, weight loss and diarrhea. Some research has even shown that some forms of good bacteria, like Saccharomyces boulardii and Bifidobacterium can help control flare-ups in ulcerative colitis.

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