What do these things have in common? Can we make worms live forever? More importantly, why would we want this?
Here’s a fun fact for your day: the activity of bacteria in your gut, and whole body (the good bacteria) are hypothesised to play a huge role in your health. You inherit these bacteria initially from your mother as you’re pushed through the birth canal, but the composition of these bacteria is affected by environmental factors such as the classic exercise and diet, and a myriad of other factors not fully understood. The totality of the bacteria you carry in your body are called the microbiome, and the composition of your microbiome is uniquely yours. Even identical twins have different microbiomes. Each bacterium is a single cell, and you are a vast, huge, multicellular organism with an estimated 37 trillion cells, so how might these be influencing your health?*
In no small part, it’s because there are more of these single-celled bacteria in your body than there are of your own cells. And it’s not even close. It’s estimated there are between 2 and 3 times as many bacterial cells in our body as there are human ones. If you want a particularly bleak (or fascinating) perspective, you might only be ¼ human and ¾ bacteria. This isn’t particularly controversial in modern health science and microbiology, and isn’t the main topic of today’s article, but it is wildly interesting and important to understand before we dive into our today’s topic, which is *checks notes*…ageing worms?
Old, old worms and optogenetics
Scientists have recently been successful in increasing the lifespan of a species of worms called C. elegans from 3 weeks to 4.5 weeks (an increase of 50%) by increasing production of a biomolecule called colanic acid. To put into perspective, increasing human lifespan by this much would give us an average age of around 120. The only problem with this was, until recently, nobody had any way of figuring out exactly why this was taking place. Enter optogenetics. Optogenetics, first engineered in 2005, uses genetic engineering to create cells which have certain reactions to certain frequencies of radiation (usually visible light). It’s mostly been used to create genetically altered neurons which respond to light, thus giving scientists good control of the timing at which neurons fired in organisms such as mice. That’s not quite how it was used here, though.
In this experiment, optogenetics was used to create E. coli (a bacteria commonly found in your gut) cells which responded to green light by releasing colanic acid. The more intensely the green light is shone, the more colanic acid is produced. Then scientists could see what was happening in the worms with higher levels of colanic acid (which were living longer). What turned out to be happening was the colanic acid was protecting mitochondria in the worm’s intestine from fragmenting under stress. Mitochondria are very important pieces of cellular machinery used predominantly to generate energy in cells. As organisms (including humans) age, mitochondria become less efficient and this makes cell function decline as the ageing process goes on.
What this means for the future of our bacteria, and us
It’s all well and good to give worms an extra week and a half of life, but due to lack of public enthusiasm about worm livelihoods, this is by no means the end goal here. This can be seen as a proof of concept, a way of showing how optogenetics can be used to do similar experiments in animals with more similarities to humans than worms, and perhaps give us a clearer idea of how our gut bacteria affect our lives, and if so, whether we might be able to artificially alter our microbiome to make us less prone to certain health conditions. This is, of course, only the beginning, and what we’ll find next is never certain to be useful. But this style of optogenetics certainly shows promise as a method of optimising our relationship with the vast population of bacteria with whom we share our body.
I hope you learnt something new!
Further reading:
https://elifesciences.org/articles/56849 - original published article
https://www.genengnews.com/news/optogenetics-turns-gut-bacterial-genes-on-and-off-inside-worms/ - contains interviews with Meng Wang and Jeffrey Tabor, two scientists closely involved in the research.
*Worth noting that despite lots of studies showing correlation between microbiome composition and health conditions, no causality has been proven as of yet, so this isn’t hard science so much as it is something scientists are currently investigating.
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