If you looked for information about Lactobacillus reuteri a few years ago, today you will find a different name: Limosilactobacillus reuteri. This is not a mistake or a new species. It is the result of one of the biggest changes to names in microbiology in recent years, made in 2020. Below, we explain where this change came from. We also explain why, when you read a label, the strain designation matters more than the species name.
Where this species lives
Limosilactobacillus reuteri is a lactic acid bacterium. This is a microorganism that produces lactic acid as the main product of fermentation. The species name honours the German microbiologist Gerhard Reuter, who studied these bacteria in the 1960s. Kandler, Stetter and Köhl published the formal description of the species in 1980.
This species has been described in the digestive tract of humans and many animals, for example rodents, pigs and poultry. It is also sometimes found in the mouth and in human breast milk.
Read more: Gut microbiota – how it develops and what shapes it throughout life
It is also found in fermentation environments, for example in sourdough starter for bread. It lives in many different places, and this is one of the reasons why it has been studied so much.
The reclassification of the genus Lactobacillus in 2020
In April 2020, the International Journal of Systematic and Evolutionary Microbiology published a paper by a team led by Jinshui Zheng. The paper divided the genus Lactobacillus into twenty-five genera. Twenty-three new genera were created, and the description of the genus Lactobacillus itself became narrower.
One of the new genera is Limosilactobacillus. The species reuteri was moved to it, together with other species. Part of the name comes from a Latin word that describes something slimy. This is linked to the fact that these bacteria produce exopolysaccharides, which are complex sugars that the cell releases outside.
| Name before 2020 | Current name |
|---|---|
| Lactobacillus reuteri | Limosilactobacillus reuteri |
| Lactobacillus fermentum | Limosilactobacillus fermentum |
| Lactobacillus rhamnosus | Lacticaseibacillus rhamnosus |
| Lactobacillus casei | Lacticaseibacillus casei |
| Lactobacillus plantarum | Lactiplantibacillus plantarum |
| Lactobacillus acidophilus | Lactobacillus acidophilus (no change) |
Why scientists divided one genus into many
The genus Lactobacillus grew for more than a hundred years, since it was first described at the start of the 20th century. Over time, it included more than two hundred and sixty species with different biology, from gut bacteria to microorganisms used in the food industry.
New methods of genome analysis showed how big the differences in this group were. The genome is all the genetic material of a cell. The authors of the 2020 paper looked at the genetic range within the old genus Lactobacillus. It was wider than the range usually found within one whole family of bacteria.
In classification, a name should show how organisms are related. The organisms with one shared name were more different from each other than their classification suggested. So the division was about putting things in order. The bacteria themselves did not change.
What this means for consumers who read the label
Most of all, it means that two different names can refer to the same microorganism. Labels and materials from before 2020 use the old names, and some manufacturers give both forms side by side.
A change of name does not mean a change in the properties of the bacteria. It also does not mean that studies must be repeated. The same strain designation refers to the same biological material, whatever genus name appears next to it.
The practical advice is simple: when you compare products, look at the strain code, not only at the species name. The strain code has stayed the same.
How microorganisms are named
Genus, species, strain
The name of a bacterium has three levels, each more detailed than the one before. The genus is the first part of the Latin name, for example Limosilactobacillus. The species is the second part, for example reuteri. The strain is the designation of a specific, isolated line of bacteria. It usually has the form of a code with letters and numbers, for example DSM 15693.
A comparison with dogs can help here. The genus is roughly like the category “dog”. The species is like a specific breed. The strain is like one single dog from a specific litter, with its own papers and pedigree.
The comparison helps to understand one more thing. Two German shepherds belong to the same breed, but they differ in character, training and history. In the same way, two strains of the same species of bacteria can differ in ways that the species name does not show.
Why the strain is more important than the species
This is the most important point of this text. In microbiology, the features described in studies are considered a property of a specific strain, not of the whole species. The ISAPP consensus statement on probiotics from 2014 states this rule directly. ISAPP (the International Scientific Association for Probiotics and Prebiotics) is an international scientific association that works on this subject.
This leads to a result that is easy to forget: observations made for one strain must not be applied to another strain of the same species. Two strains of Limosilactobacillus reuteri can differ in their genome, in the metabolites they produce and in how they behave when they grow.
That is why a phrase such as “studies on Limosilactobacillus reuteri have shown” is not precise from the point of view of research methods. A correct reference always names the specific strain with its designation.
The same rule applies to inanimate preparations, which means preparations without cells that can multiply. The definition of a postbiotic that ISAPP published in 2021 requires the source microorganism to be identified at the level of the strain, not the species.
Read more: Postbiotics – what they are and how they differ from probiotics and prebiotics
Where codes such as DSM come from
Codes that start with an abbreviation such as DSM, ATCC, CNCM or LMG are catalogue numbers from strain collections. Collections are institutions that store isolated lines of microorganisms and make them available for research and industrial use.
The abbreviation DSM refers to the German collection Deutsche Sammlung von Mikroorganismen und Zellkulturen, based in Braunschweig. ATCC is the American Type Culture Collection. CNCM is the French collection run by the Pasteur Institute, and LMG is a Belgian collection.
When a strain is deposited in a collection, it means that it has been described and is available in a form that can be reproduced. The catalogue number works as an identifier. It lets you check whether a scientific publication and a specific product refer to the same line of bacteria.
Read more: What the code after a bacterium’s name means and why the strain designation matters
One example of a product that refers to such a designation is THESYBIN food supplement. It contains OLINATI.MED® — a fermented strain of Limosilactobacillus reuteri DSM 15693, with added zinc and vitamin B5. Thesybin does not contain live bacteria.
Summary
The change of name from Lactobacillus reuteri to Limosilactobacillus reuteri comes from the reclassification in 2020. At that time, the old genus Lactobacillus was divided into twenty-five genera. The bacteria themselves did not change. Their place in the classification changed.
For a person who reads the label, the main practical point is this: older and newer materials can use different names for the same microorganism. The strain code stays the same.
The most important rule is still that the features described in studies are a property of a specific strain, not of the species. The species name tells you which group a bacterium belongs to. It does not replace data about a specific, identified line.
FAQ
Are Lactobacillus reuteri and Limosilactobacillus reuteri the same?
Yes, it is the same species with two names. The first name was valid until the reclassification in 2020. The second is the current name. The change was only about which genus the species belongs to. The bacteria themselves did not change in any way.
Why do some packages still show the old name?
Printed materials and descriptions published before 2020 use the old names, and it takes time to update packages and websites. Some manufacturers give both names side by side to make the product easier to recognise.
Are all strains of the same species the same?
No. Strains of one species can differ in their genome, in the metabolites they produce and in how they behave when they grow. For this reason, observations about one strain do not automatically apply to other strains of the same species.
What exactly does the number after the strain name mean?
It is a catalogue number from the collection of microorganisms where the strain was deposited. It identifies a specific line of bacteria clearly. It also lets you check whether a publication and a product description refer to the same material.
Sources
- Zheng J., Wittouck S., Salvetti E. et al., A taxonomic note on the genus Lactobacillus: Description of 23 novel genera, emended description of the genus Lactobacillus Beijerinck 1901, and union of Lactobacillaceae and Leuconostocaceae, International Journal of Systematic and Evolutionary Microbiology, 2020, vol. 70, no. 4, pp. 2782-2858.
- Hill C., Guarner F., Reid G. et al., Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic, Nature Reviews Gastroenterology & Hepatology, 2014, vol. 11, no. 8, pp. 506-514.
- Salminen S., Collado M.C., Endo A. et al., The International Scientific Association of Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of postbiotics, Nature Reviews Gastroenterology & Hepatology, 2021, vol. 18, no. 9, pp. 649-667.
- Commission Regulation (EU) No 432/2012 of 16 May 2012 establishing a list of permitted health claims made on foods, other than those referring to the reduction of disease risk and to children’s development and health.
- Kandler O., Stetter K.-O., Köhl R., Lactobacillus reuteri sp. nov., a new species of heterofermentative lactobacilli, Zentralblatt für Bakteriologie: I. Abt. Originale C, 1980, vol. 1, no. 3, pp. 264-269.
- The LPSN database (List of Prokaryotic names with Standing in Nomenclature) run by DSMZ, https://lpsn.dsmz.de, and the catalogues of strain collections (DSMZ, ATCC, CNCM, LMG).