It is quite probable that you’ve heard from the benefits of yoghurt and other probacteria containing foods for your health, even more so it is probable you take them already regularly. What if these probiotics would also help maintain your biological integrity, that is, would prevent aging?
This is not quite a random question, actually this was the exact question that a group of researchers set out to investigate. In their article, Veronica Donato and colleagues, tried to examine the effects of a common probacteria in animal guts from worms to cows to us, Bacillus subtilis, in the longevity of C.elegans, a small worm commonly used for genetic studies and longevity, since their usual lifespan is around 2-3 weeks, short enough to be able to replicate experiments in a reasonable time span.
These bacteria are known to grow and produce biofilms, which are 3D structures formed by biological organisms and encapsuled in a self-produced matrix. For their experiments, the researchers used two strains of bacteria, a wild type, that is a natural sort, and one mutagenized in the lab. Wenn they used spores (resistance form) of these 2 types of bacteria to feed the worms instead of their usual E.coli, they found a significant life extension in comparison to the E.coli feeding. This effect was stronger in the wild type B. subtilis treatment as in the mutant, even though spores were undistinguishable in their properties and no changes in worm behaviour were found in the mutant spore feeding group.
Not only did this bacterial feeding (either with wild type or mutant) extended worm lifespan but also increased their resistance to thermal and other types of stress (including osmotic, heavy metal and oxidative stresses), even though the wild type had stronger beneficial effects on lifespan and stress resistance as the mutant. To address the origin of these differences, the investigators developed a series of test that led them to conclude that the main difference comes from the gut colonization rates of the two types of bacteria.
In order to characterize the influence of biofilm formation on succesful gut colonization of the B. subtilis bacteria, an experiment with mutated variants of the wild type strain, where some relevant genes for biofilm formation were removed, showed that feeding bacteria incapable of biofilm formation reduces the lifespan expansion potential of this bacterial feeding strategy, probably due to their reduced capability of gut colonization.
It has been shown that NO (nitric oxide) production could be a possible mechanism of life extension in C.elegans. By a combination of mutation experiments, it was shown that the level of implication of NO and biofilm formation in the increased longevity is different. Mutations affecting NO production by B.subtilis resulted in a less pronounced decrease of life extension as mutations to biofilm formation. When combined, these 2 mutations caused the strongest impairment to increased longevity. Therefore, these mechanisms are different but have summatory effects on aging.
Another factor in the longevity effects seen by B.subtilis biofilm was a certain signalling molecule produced by cells within the biofilm. Further experiments confirmed that it is this biofilm conformation that allows for the ideal production of NO and this other signalling molecule, thus leading to the observed anti-aging events. Moreover, they found differences in the effects depending on whether bacteria were alive or dead, confirming the importance of live bacteria in the worm’s gut for life extension.
The last part of their article shows evidence for a link between activity of DAF-16, DAF-2 and HSF-1 (anti-aging elements, part of the insulin-like signalling (ILS) pathway and the caloric restriction pathway leading to extended lifespan) and the beneficial effects of the B.subtilis biofilm on C.elegans longevity.
In summary, probiotic feeding of biofilm bacteria (B. subtilis) leads to an extended lifespan in C.elegans via the ILS pathway. Another really important point from this work is that ONLY live bacteria lead to beneficial effects, that not being the case if the bacteria are dead. Why is this important? Because as much as the food industry insists to sell us yoghurt as probiotic , it is common that most of the bacteria in these foods are dead or do not reach the intestine. In any case, it is worth investing in taking good care of out gut flora, be it with yoghurt, probiotic drinks or else.
Nature Communications 8, 14332 (2017). Bacillus subtilis biofilm extends Caenorhabditis elegans longevity through downregulation of the insulin-like signalling pathway. Donato V. et al.
Microb Ecol Health Dis. 2012; 23: 10. Probiotic viability – does it matter? Sampo J. Lahtinen