Underground wars and genetic treasures 

SynCell News • July 28, 2020

Where would it be easier to be exposed to antibiotic-resistant bacteria? Your answer would most likely set the location in a hospital setting, closely followed by a developing country animal farm or the water stream coming from an antibiotic industry. Now, where would you go if you wanted to be completely shielded from those superbugs?

95% of the Earth’s land surface has some indication of human modification

Likely, you would try to find an isolated place, ideally, a location that has not been exposed to any human beings. This means that no antibiotics have been used to fight the present bacteria. Leaving the underwater alone, a recent study found that 95% of the Earth’s land surface has some indication of human modification, while 84% has multiple human impacts [Hooke and Martín-Duque, 2012]. Therefore, if you want to avoid contact with antibiotic-resistant bacteria, your answer should place you in that 5%.

It turns out that such a small percentage if full of caves. The truth is that there are countless “virgin caves” around the world, which means that no human being has set a foot there. Therefore, there we have it: our perfect isolated place to avoid antibiotic-resistant bacteria.

However, nature comes again to prove you wrong.

Researchers have discovered an ancient bacterium that is resistant to many antibiotics

A thousand feet under the New Mexico soil, we can find Lechuguilla Cave, the eighth-longest cave in the world and the second deepest in the continental US. What is unique about this cave? Within its almost 140 miles, researchers have discovered an ancient bacterium that is resistant to many antibiotics used in human medicine today [Pawlowski, 2016].

It is now the time to meet Paenibacillus sp LC231, a facultative anaerobic non-pathogenic bacteria that was initially identified in 2012 in the deepest parts of the cave. When brought to the lab, the bacterium was full of antibiotic resistance genes, which gave the microorganism the ability to resist 26 of 40 antibiotics tested, including daptomycin, a powerful antibiotic discovered in the early 1980s [Buhllar, 2012].

Well, it seems odd to find this kind of behavior in a bacterium in an isolated cave. Still, it becomes even stranger when you realize that the microorganism has been sealed off from human or animal contact for more than 4 million years [Craig, 2016].

Then, how is it possible that a bacterium that has had no contact with human beings show resistance to drugs that we started to re-discover in 1928 from natural sources?

Once more, the answer is nature. Resistance to antibiotics is a natural consequence of evolution. Therefore, human misuse and overuse of antibiotics are not the sources of resistance, but an accelerating factor of this healthcare problem in selected settings.

Bacteria created antibiotics billions of years ago; hence, resistance is primarily the result of bacterial adaptation to millions of years of antibiotic exposure without human intervention. Consequently, natural selection gives rises to antibiotic resistance through what is known as environmental pressure –in simple words, those bacteria that have the mutation to thrive in the presence of the antibiotic will survive, while the rest will not; those who survive to pass this trait to their offspring, and then life continues.

Then, in the deepest of the cave, Paenibacillus sp LC231 might be the strongest and fittest bacterial strain after a relatively crude antibiotic selective pressure that has been happening for millions of years.

Why is this good? The cave might be thriving with small subpopulations of antibiotic-producers bacteria—those who fight along and against our bacterial protagonist. Therefore, the darkness of the underground world, which harbor ferocious superbugs, might also be the key to the development of new antibiotics.

However, when seeking these new antibiotics, we should be aware that we are just isolating a byproduct of a long war. After billions of years of evolution, bacteria have most likely produced and use antibiotics against every biochemical target that can be attacked, hence developed resistance mechanisms to protect all those biochemical targets.

Consequently, we might seek alternatives without turning back to the source of potential solutions. One way or another, bacteria might suppose the key to a door to the future, and it is up to us whether this door led to a dystopian AMR crisis or a brighter future.