What is Firmicutes bacterium CAG:170 and why is he a ‘good’ bug?

ZOE runs the largest study of nutrition and gut bacteria in the world, with data from over 15,000 people. We publish our research in top scientific journals, including Nature Medicine. Our scientists have found 15 “good” gut microbes that are associated with indicators of good health and 15 “bad” gut microbes that are linked with worse health. 

Firmicutes bacterium CAG:170 — or “Finn” as we call him — is one of the 15 “good” bugs. In this article, you can find out more about Finn, why he is a good bug, and what foods he likes and dislikes. 

Fast facts about your gut microbiome

  • Your gut is home to trillions of bacteria and other microbes that make up your gut microbiome.

  • These microbes mainly feed on fiber and chemicals called polyphenols, which give plants their color, and turn these into chemicals that help support your health and weight control. 

  • Your gut microbiome is unique and radically different from everyone else’s, unlike your DNA, which is 99% the same. Even twins only share 34% of the same microbes. 

  • At ZOE, we use the latest and most advanced biotechnology to analyze the bacteria in your gut from a poop sample.

  • Using this technology, the ZOE program tells you your unique microbiome composition — including which of the 15 “good” and 15 “bad” bugs are in your gut — in order to recommend the best foods for you.

Who is Finn?

Finn is part of a group of bacteria called Firmicutes. If you looked at Finn under a microscope, you would see that he is shaped like a rod.

Our scientists found Finn in the gut of about one-third of study participants. 

Other members of the Firmicutes include Lactobacillus, which you may be familiar with already. They are “good” bugs found in foods like yogurt. 

Why is Finn a ‘good’ bug?

Scientists don’t know much about Finn yet because he was only discovered very recently. 

In our study, we found links between having Finn in your gut and having higher insulin sensitivity.

Higher insulin sensitivity is good for your body because it helps regulate your blood sugar levels. Too much insulin and low insulin sensitivity are bad for your health, as they increase your risk of obesity, type 2 diabetes, and heart disease. 

We also saw links between Finn and a lower risk of cardiovascular disease, one of the leading causes of death in the United States and worldwide.

What foods does Finn like and dislike?

Our scientists have found links between specific foods that you eat and the 15 “good” and 15 “bad” gut bugs.

Great foods for Finn are eggs, nuts, and dark chocolate. He doesn’t like sugary cereals.

But the exact foods that will help Finn thrive in your body depend on the combination of bugs in your gut. Since every person’s gut microbiome is completely unique, there is no one-size-fits-all diet that is right for everyone. 

The ZOE program analyzes your entire microbiome and works out your unique gut booster and bug suppressor foods, so that good bugs, like Finn, can flourish.

If you want to know the best foods for your body and your unique combination of gut bugs, take our free quiz today. 


Insulin: Too much of a good thing is bad. BMC Medicine. (2020). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7441661/

Leading causes of death. (n.d.). https://www.cdc.gov/nchs/fastats/leading-causes-of-death.htm

Microbiome connections with host metabolism and habitual diet from 1,098 deeply phenotyped individuals. Nature Medicine. (2021). https://www.nature.com/articles/s41591-020-01183-8

The top 10 causes of death. (2020). https://www.who.int/news-room/fact-sheets/detail/the-top-10-causes-of-death