In a healthy vaginal microbiome, one of four species of lactic acid bacteria almost always dominates the community. Coincidentally (or not), all four species belong to the bacterial genus Lactobacillus. This genus is very diverse, to an almost absurd extent: the species within this genus differ much more from each other than the species of any other bacterial genus.
Imagine a similar situation in the aminal kingdom. We would then, for example, only speak of mammals, and there would be no separate terms for smaller groups such as carnivores, marsupials, primates. Each of these smaller groups has a shared evolutionary history and one or more unique characteristics. For this reason, we would like to be able to refer to such groups by name.
The same is true for smaller groups of bacterial species within the genus Lactobacillus. That is why, together with a large international team of researchers, we have split Lactobacillus into 25 smaller genera. Each of these genera has its unique, specific characteristics. For example, all species of the new genus Limosilactobacillus are found in animals’ intestines. As another example, species of the new genus Fructilactobacillus often live in insects and love fruit as a food source. The split of the genus Lactobacillus is now official since it was published in the International Journal of Systematic and Evolutionary Microbiology (IJSEM).
Because the name of a bacterial species consists of the genus name followed by a species-specific suffix (e.g., Lactobacillus crispatus), many Lactobacillus species now change names. For example, the bacteria in your bottle of Yakult will be called Lacticaseibacillus casei instead of Lactobacillus casei. Fortunately for the food industry, most new names still start with an L; for example, Yakult can continue to use the abbreviation L. casei.
So far, the big news. But…
The names of vaginal lactobacilli do not change
Coincidentally, the vaginal Lactobacillus species all belong to the chosen group that gets to keep the name Lactobacillus. The reason for this has everything to do with the species Lactobacillus delbrueckii. This bacterium is partly responsible for making yogurt, and it was the first Lactobacillus species to be officially described (by the Dutch microbiologist Martinus Beijerinck in 1901). Since most vaginal lactobacilli are closely related to this yogurt bacteria and thus belong to the same new genus, they simply continue as Lactobacillus. Whether this means that eating (or even smearing) yogurt (as some DIY blogs on the internet recommend) is better for your vaginal microbiome than a bottle of Yakult or other probiotics is not yet clear from the current literature. Who knows, we might see that in the results of Isala!