What is Faecalibacterium prausnitzii and why is she a ‘good’ bug?

ZOE runs the largest study of nutrition and gut bacteria in the world, with data from over 10,000 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. 

Faecalibacterium prausnitzii — or “Felicia” as we call her — is one of the 15 “good” bugs. In this article, you can find out more about Felicia, why she is a good bug, and what foods she 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 Felicia?

Felicia is part of a group of bacteria called Firmicutes. She is one of the most common bacteria in the gut, and if you looked at her under a microscope, you would observe that she is shaped like a rod.

In fact, our scientists found Felicia in the gut of nearly everyone — 99.7% of our study participants, to be precise. 

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 Felicia a ‘good’ bug?

Felicia is one of the main bacteria that turn the fiber that you eat into butyrate. This is a molecule that is important for your gut health and may lower your risk of colorectal cancer and inflammatory bowel disease. 

In our study, we saw links between having Felicia in your gut and having lower insulin secretion and higher polyunsaturated — or healthy — fat levels.

Lower insulin secretion is good for your body. Too much insulin is bad for your health, as it increases your risk of obesity, type 2 diabetes, and heart disease. 

What foods does Felicia like and dislike?

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

In general, high fiber foods — like fruit, whole grains, and nuts, as well as vegetable oils and dark chocolate — are great for Felicia. She doesn’t like sugary drinks or animal-derived food. 

But the exact foods that will help Felicia 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 "gut suppressor" foods, so that "good" bugs, like Felicia, 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. 


Faecalibacterium prausnitzii: from microbiology to diagnostics and prognostics. The ISME Journal. (2017). 


Insulin: Too much of a good thing is bad. BMC Medicine. (2020).


Microbiome connections with host metabolism and habitual diet from 1,098 deeply phenotyped individuals. Nature Medicine. (2021).