Probiotics are dang tricky. To start the conversation, you must understand all about probiotic strains and species.

Yes, this topic is sort of geeky, but nonetheless it’s an important one.

The Gates of the Stomach: History

I think you’ll enjoy this to start the post off.

Just Thrive Probiotic

It was 2018 when I began my final SIBO relapse.

My stomach felt grumpy more often than not, and I knew it was back.

So shortly before heading to Expo West that year when I felt the slightest hint of stomach discomfort, I began doing all the things. The main things I did:

  1. Dysbiocide
  2. My daily mantra, “You are healed. Your SIBO is gone, and you’re feeling incredible.”
  3. Strict on the 12-14 hour daily fasting + meal spacing
  4. NO probiotic

But then I got to Expo West and the very first night I met Kiran Krishnan.

I told you that meeting him was an Expo West highlight. He and I discussed all things microbiome, SIBO, why long-term restrictive diets cause more harm than do good, and…..probiotics. 

Due to his extensive knowledge and adamant stamp-of-approval for the Just Thrive Probiotic, I immediately (like at the show) started taking their probiotic. Literally within a couple days, back to zero gut issues (don’t get me wrong, it was likely the combination of everything I did).

The point is that, I now believe taking a probiotic (strategically like the Just Thrive Probiotic) can in fact help – immensely – no matter where you’re at on your gut-healing journey.

Note: If you like the information I’m providing on the Jut Thrive Probiotic, you can grab it HERE and if you put in code ‘AGUTSYGIRL‘ at checkout, you’ll automatically save 15% off your entire order.

Who is Kiran Krishnan?

All About Probiotic Strains and Species SKH and Kiran Krishnan #probiotic #probiotics #supplements #SIBO

Before I even get into probiotic strains, I want you confident right along with me that Kiran is legit.

Microbiome Labs

Kiran Krishnan is a microbiologist and researcher on Soil Based (Spore-based) Probiotics and designed the formulation in MegaSporeBiotic from Microbiome Labs. (source) He has been involved in the dietary supplement and nutrition market for the past 15 years.

He comes from a strict research background having spent several years with hands-on R&D in the fields of molecular medicine and microbiology at the University of Iowa. As a microbiologist, he has a deep understanding of microbial science and has spent the last 8 years studying the strains used in Just Thrive® Probiotic & Antioxidant. (source)

In addition to his recently published, ground-breaking leaky gut study showing reversal of gut enteropathy within thirty days, Kiran is currently involved in nine other ongoing human clinical trials testing the effect of gut commensal spore probiotics on many conditions including, Thyroid/Hashimoto’s, Irritable Bowel Syndrome and Liver Failure, as well as a longer, more extensive Leaky Gut trial. (source)

You’ll find Kiran on several podcasts and stages worldwide speaking about everything he knows. 

In fact, you can listen to him on my podcast right now if you want!

So when I say he’s legit, and I start giving information found via Just Thrive through him, I promise you can trust it.

Well, I at least did, which is why I’m here to share with you now.

All About Probiotic Strains and Species

Click HERE to save this post for later.

All About Probiotic Strains and Species #probiotic

To review what a probiotic (vs. prebiotic) is, read THIS.

Probiotic strains matter because each strain has unique properties. Depending on what those properties are and what they aim to do will determine if it’s right for you. 

This is why any old probiotic will not work, which is something I tried to demonstrate first when I wrote Should I Take a Probiotic with SIBO?

All About Probiotic Strains and Species #probiotic #guthealth #probiotics #SIBO genus species strain

When looking at a probiotic label, you will either see two or three words. These two or three words include some or all of the following: genus, species, and strain.

An example of two: Lactobacillus (genus) acidophilus (species)

An example of three: Bacillus (genus) Subtilis (species) HU58 (strain)

When you see two, that means they have only provided the species, not the strain of probiotic being used.

And when you see three, like Bacillus Subtilis HU58, you’re getting more information about the strain.

Bacillus Subtilis HU58 + Bacillus Indicus HU36

Below are the four strains you’ll find in the Just Thrive Probiotic (source):

Bacillus Subtilis HU58

Bacillus Subtilis has been extensively studied on a genetic and functional level. There are several probiotic products in the pharmaceutical and agricultural markets that utilize this powerful probiotic.

One very interesting function of Bacillus Subtilis is its ability to produce nearly 12 strong antibiotics that are potent fighters of opportunistic and harmful bacteria. This is part of its wide use in high level feed products.

Bacillus Subtilis HU58 offers Just Thrive® the ability to support the prevention of harmful bacteria growth in a variety of conditions.

In addition, HU58 produces a very healthy compound called Nattokinase in your digestive tract.

Nattokinase is a key compound found in the Japanese food Natto that uses Bacillus subtilis for the fermentation of soy beans.

The serine protease known as Nattokinase is secreted from vegetative cells of Bacillus subtilis and has been shown to support healthy blood pressure, support healthy cholesterol levels and support healthy circulation.

Along with Nattokinase, Bacillus Subtilis also produces a number of other nutrients that have systemic health benefits. In addition, Bacillus Subtilis HU58 is an extremely potent immune stimulator.

It has the function of germinating in the small intestines to some degree and this offers the effect of broad spectrum immune stimulation. It has also been shown to increase the growth of your natural good bacteria.

This strain is recommended for travel

Additionally HU58:

  • 100% survivability in the digestive tract
  • 40% increase in short-chain fatty acid (SCFA) production
  • Maintains healthy digestion
  • Supports healthy immune function
  • Effective during antibiotic therapy

This is why, when someone reached out yesterday about this probiotic during and after Rifaximin and Neomycin, I said, “All the yes.” (Also, because I know that Dr. Michael Ruscio recommends it as well and he works so much with SIBO patients.)

Thrive Probiotic

So what is the game changer in the Just Thrive Probiotic?

Here’s your answer.

Bacillus Indicus HU36

The Bacillus strain found in Just Thrive® that makes it a real game-changer in the probiotic market is Bacillus Indicus HU36 (Bacillus HU36). Bacillus HU36 is a well-studied, unique, patented strain of Gram-positive spore forming bacterium that produces a distinct yellow-orange pigmentation.

The pigmentation is due to the synthesis of carotenoids, which are gastric stable, bio-accessible, and significantly more bioavailable than carotenoids from other sources. Bacillus HU36 offers Just Thrive® the most effective antioxidant probiotic on the market. Bacillus HU36 produces high levels of carotenoids such as Lycopene, Lutein, Astaxanthin, Zeaxanthin and Beta-Carotene. Along with these crucial antioxidants, Bacillus HU36 also produces quinols and essential vitamins B and K2.

Just Thrive® is the first and only probiotic and antioxidant product on the market today, making it the new paradigm in probiotic therapy.

– Potent immune stimulation.
– Produces high levels of carotenoids – lycopene, axtaxanthin, beta-carotene, and lutein.
– Produces quinols and vitamins.
– The most effective antioxidant probiotic on the market.

More on HU58 and HU36

Do you want more on HU58 and HU36?

My favorites are below, but you can grab the full thing HERE:

  1. Both strains naturally survive the stomach and immediately germinate in the upper GI. This seems like a simple point, but considering that many studies show that most commercial strains don’t even get pass the stomach, this is an important feature to prove.
  2. Both strains are well suited for life in the GI and colonize effectively. If it can’t colonize, it’s not a probiotic. This has to be proven, most people just assume their probiotic colonizes.
  3. Best germination occurs when taken with food. Most probiotics recommend taking it on an empty stomach due to the pH. This is stable enough to be taken with food and in fact the probiotics utilize the food to germinate.
  4. Both showed increased saccharolytic fermentation over proteolytic which favors lowered pH (beneficial pH change for the GI) and does not produce gas (which can be an issue for many probiotic supplements).
  5. They both strains produce significant amounts of short-chain fatty acids (SCFA) from carbohydrate digestion – in particular there is an increased production of acetate initially and then higher levels of butyrate in longer term use. 
  6. Both strains showed the ability to alter the entire microbiota – this is unique for a probiotic to have demonstrated the ability to alter the microbiota. This has profound implications on the types of claims that can be made as far as the probiotic benefits of these strains. The Human Microbiome Project has shown that all diseases correlated to the gut comes from a dysbiosis in the gut. That means the balance of good and bad bacteria is off. 
  7. The HU36 strain has now been verified to produce RDA levels of carotenoids in vivo – this is a powerful dietary source of antioxidants. 

The Other Two Strains

The other two strains (Bacillus Clausii SC -109 + Bacillus Coagulans SC-208) in the Just Thrive Probiotic are currently listed on the bottle as species. I reached out to the company on this, and they informed me that all four are actually strains; just not yet reflected on the label.

Make note that the label will be updating soon to reflect this strain and not just the species. Here is the information we know about the species as whole (extracted this from Dr. Amy Myer):

  1. Bacillus Clausii:
    • Helps modulate your immune response
    • Assists in IgA synthesis
    • Antibiotic resistant for use with antibiotic treatment of SIBO
    • Produces bactarin, a weapon against pathogens
  2. Bacillus Coagulans (B. Coagulans):
    • Helps the good bacteria successfully colonize in your gut
    • Potent immune stimulator
    • Long history of studied use in IBS, Crohn’s, and ulcerative colitis

Thus, if SIBO (or many other Gutsy conditions) is what you face daily, one could conclude that this probiotic could be the one you’ve been looking for.

Don’t think that these four probiotic strains and species above are the only ones out there, though.

There are far too many to count, but here are 13 common ones you may have seen (and/or currently use). 

Probioticos: 13 Common Probiotic Species

Click HERE to save these for later.

And please remember, these are the species not the exact strains.

All About Probiotic Strains and Species #probiotic #lactobacillus


  • clausii
  • coagulans
  • indicus
  • subtilis 


  • bifidum
  • breve
  • longum


  • acidophilus
  • casei
  • paracasei
  • rhamnosus

Saccharomyces boulardii

Streptococcus thermophilus

Please remember: quantity does not always correlate to quality. More strains in a probiotic doesn’t necessarily mean it’s better.  

Now, go check out the 8 Probiotic Myths as dispelled by Kiran Krishnan.

Follow up: Is there a genus, strain, or species in your current probiotic that you’re wondering about? Leave it in the comments below or CONTACT ME so I can look into it for you. Because remember, to eat a steak, you’d never use a spoon. 

Disclosure: When you purchase Just Thrive via any of the links in this post, I am paid a small affiliate commission. All opinions stated here are 100% my own. I appreciate your support, as this compensation helps with expenses to keep this blog up and running, and for me to continue sharing all that I can with you. For my full disclaimer and disclosure click HERE. Thank you for your support!

If you liked this post, you might also enjoy:

  1. All About Just Thrive Probiotics
  2. All About Prebiotics
  3. What to Expect When Starting Probiotics
Probiotic Strains and Species #probioticos #probiotics #probioticsupplement


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  1. I struggle when taking probiotics. I have taken Align an I feel like my gut gets worse. Every probiotic I’ve taken I have diarrhea with. I need help of how to heal my gut as well as getting a probiotic that will work for me. I have terrible allergies. I’m allergic to molds foods etc. I’ve had ulcers colitis. I just wanna get better and not struggle with these issues. My sinuses are always bad due to my gut issues.

    1. Hi Belinda – I feel for you! Some info you might find useful on Align. Bifidobacterium Infantis is what the Probiotic contains. That, in and of itself, might be okay, but here are the other ingredients found within the product: {Other Ingredients: Microcrystalline cellulose, hypromellose, sucrose, magnesium stearate, sodium caseinate, titanium dioxide (color), trisodium citrate dihydrate, propyl gallate (antioxidant preservative), gellan gum. Contains: Milk.} I might guess that the other ingredients are contributing to your continued problems. Compare those to the “other” ingredients in Just Thrive –> Hope that helps. Xox

  2. Hi, Sarah – I’ve been intrigued by and have taken probiotics for 10 years, different brands and strains. I’ve noticed some work for awhile and then I go through seasons where all my IBS symptoms come back and they don’t do anything (or seem to make it worse). Have you found any information that recommends switching types of strains or formulas due to the exact symptoms you’re experiencing at the time? Or is it best to stay on the same formula and examine other factors to adjust (diet, seasonal allergy flare ups, stress, etc.)? Also, I had read that B.Infantis strains are extremely beneficial in treating IBS-D. Have you come across any research on that? I’m currently taking Garden of Life Dr. Formulated once daily (30 billion), and then switch to the similar formula that’s shelf stable for travels. They seem to help, but nothing is 100%…

    1. Hi Kathyrn! Great questions. re. “Have you found any information that recommends switching types of strains or formulas due to the exact symptoms you’re experiencing at the time?” –> Yes, I have addressed that in the post – different strains and species are targeted to help different conditions and symptoms. That said, your symptoms at any given moment in time might have more to do with those other lifestyle things you mentioned.

  3. I do not have sibo but my test came back that I could have methane induced Constipation. I do have a Candida overgrowth that I’m dealing with but as a nursing mother this is very difficult. When I take a probiotic (hmf forte hmf 500) my stomach gets so bloated it’s unbearable more than my normal bloated stomach. Suggestions?

    1. Hi! I would go back to the drawing board on the probiotic. I have never heard of that probiotic, so you might want to check into the strains, species + “other ingredients” contained in it. I see they claim 500 billion – that might be way too much for you currently.

  4. Hi Sarah, I am also trying to educate people about intestinal health here in germany, as i myself am affected by (Crohn’s). I’m interested in your opinion on Natren Probiotika’s Natasha Trenev’s statement that it’s better to start by taking only single strands instead of many at once. And must Thrive also be cooled? Or are the statements about value already outdated? Thank you very much for your effort and care in your contributions. I also like your style very much 🙂 Many greetings Claire

    1. Nice to e-meet you, Claire! I have a lot of information for you. Sorry if it’s an overload 🙂

      The majority of studies are done on single strains which may why this belief is out there. For example, there are great studies on lactobacillus rhamnosus GG but you can’t add lactobacillus rhamnosus to a formulation and make the claims that are supported in the study on the GG strain. With Just Thrive, the studies were on their specific formulation – the consortium of the strains vs. a single strain. The strains in Just Thrive work synergistically because they have done multiple clinical trials on this formulation of strains. There would be no reason to start taking them as a single strain unless it was a cost issue (which isn’t an issue).

      Just Thrive never needs to be refrigerated. In fact, a probiotic that needs to be refrigerated is a sign of a weak probiotic (p.s. I’m proving this in my 8 Probiotic Myths post coming soon). If a probiotic is not able to stay alive at room temperature on the store shelf, then how will it stay alive when it gets into your body at 98.6 degrees? It won’t. Just Thrive is in its dormant state in the capsule and remains dormant as it travels to the intestines, which is how it is able to survive the harsh conditions of the gastric system. It’s not until the strains get to the intestines that it takes its endospore shell off and goes into its live vegetative state, where they colonize and remain in the intestines for 21-28 days. The strains in Just Thrive are so robust that they can even be baked with!

      Did I hear probiotic recipes calling my name?! 🙂

      1. Well this arguement sounds very true to me. But how do the strains know that they are in the intestines than? Baking with probiotics?! wow very cool. I cant wait to try this by myself. 🙂
        all this gut stuff is so extremly faszinating to me, so there is absolutly no reason to apologize for a lot of information. 😉
        So thank you very much Sarah. Now I am heading to your new post…

  5. Dear Sarah, I hope you and you family are doing well. I wanted to thank you soooo much for your posts. You are more informative than any MD or gastrologist that I have seen. I just stopped taking Total Response probiotic. I had 2 flare ups while taking it. I just got Just Thrive in the mail. I was going to send it back because I’m so bummed that Total Response didn’t work. Then I just read your info on Just Thrive and I am definitely going to start taking it. Thank you again for all of the research you do on the guts and pass it on to us.
    Lenore Perez

  6. Hi Sarah, I am looking into BIO-X4 and was wondering your take on it. I also did some research and read that DR Gundry said that a probiotic won’t work unless you are taking a Prebiotic with it.

  7. So Just Thrive Probiotic is better than MegaSporeBiotic? Did Kiran Krishnan help develop both of them? What is the difference in them? Thanks.

    1. Hi Debbie!
      Megaspore is their sister company and only available to practitioners, Just Thrive is the retail version of Megaspore. They work extremely closely together. All of the Just Thrive research and studies are conducted with both products.

      They have the exact same 4 key strains as Megaspore in the exact same amounts.

      Both products have the game changing antioxidant producing strain, Bacillus Indicus HU36. The only difference is Megaspore has a small amount of the strain, Bacillus Lichenformis. Bacillus Lichenformis is a strain that Kiran felt should be taken under a doctors or trained professionals care. It produces the antibiotic bacitracin, as well as some digestive enzymes. Just Thrive is available to everyone where MegaSpore can only be obtained through a practitioner and is a bit more expensive.

      Hope that helps!

  8. I ordered 2 bottles of thrive whilst travelling in the car and forgot to put in the discount. Do you still get something out of it?
    I love your work and l recommend people to read your info to empower themselves. I work in a health food shop and l want to advise products that l believe in. That’s hard when we don’t stock American products only Australia. Looks like l need to read some more labels.
    Love your work.

  9. Hello Sarah,

    Are these strains from judt thrive found naturally in the gut? I see conflicting articles online about the positives/negatives of probiotics that do not naturally reside in the human gut. Was hoping to get your perspective on this. Thank you

  10. I recently noticed that my doctor prescribed probiotic has chickory root and that is
    An ingredient that I had to eliminate….. it was a main ingredient in Kind bars which aggravated my dual IBS. I replaced it as advised with another one made for children but it contains lactose. The pharmacy is now researching to find one that doesn’t contain these two ingredients. I will mention Thrive to the GI on Friday. He is young and very wellness, prevention oriented…. as miserable as I was he has helped me immensely without even one invasive procedure! I just can’t feel right with these probiotics and swear they make me have a flare up. Also my mild rosacea is worse when I have a flare up but also I swear the probiotic triggers a flare up on my face. I’m an otherwise healthy and fit 62!year old and am recovering from 4 decades of bulimia issues……. nonprofit Ken with that anymore but getting my gut well is work.

  11. What works for one person won’t work for another, and could make that person much, much worse. On three separate occasions — weeks apart — I took “Just Thrive” and experienced SEVERE diarrhea. Happened every time.

    Kiran Krishan is smart, but he’s also a charmer, that’s for sure. Sarah clearly fell for that, as have many others. It’s worth noting that his company funds all their studies, except for one from Romania. That’s one of the reasons his gimmicky probiotic is SO incredibly expensive.

    The other is that he pays himself very well. I still remember a Facebook post of his where he showed of his $600+ tennis shoes.

    Sorry, I’ll pass. Pun intended.

    1. Hi Kelly – I’m sorry for your experience. I think any sort of discourse on posts I write is fantastic. And for that, I do thank you for stopping by and sharing your thoughts. Perhaps you do or don’t know my beliefs on gut health and gut healing, but the greatest believe I have is exactly as you said – what works for one person won’t work for another.

      That said, I did not “fall” for anything. Look around my site into all the various research I’ve done. If this was about me falling for some “gimmick,” then thousands of other people who love and use Just Thrive religiously are also falling for the gimmick.

      I couldn’t care less how much Kiran’s shoes are, and believe that is no indication as to the quality someone puts out into the world.

      I wish you the best.

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