Gut bacteria is important—like really important. The trillions of bacteria in our digestive tracts help to support immune health, extract nutrition from foods, and can even help remove toxins such as heavy metals. Bacteria binding to heavy metals isn’t a new concept but bacteria common to the human digestive tract is.
Metal Chelation 101
“Heavy Metals” is a misnomer used to describe a class of elemental compounds known to cause deleterious effects on human health. Common among these are compounds such as arsenic, lead, mercury, and cadmium. These are the “big 4” and the subject of most heavy-metal-toxicity discussions.
There’s a risk factor of anything in excess—even oxygen or water—but many metallic compounds are found in environmental concentrations that make them more feasible as potential contaminants. For example, water poisoning would involve some red-flag circumstances while compounds like Manganese could fly under the radar.
“Chelation” is the term used to describe the process of removing toxic metals from the body. Ethylenediamine-tetraacetic acid (EDTA), 2,3-dimercaptosuccinic acid (DMSA), and sodium 2,3-dimercaptopropane 1-sulfonate (DMPS) are three common agents used to treat metal toxicity. In addition to metal toxicity, compounds like EDTA are thought to help deal with arterial plaques, though the Science is debated.
Quick Summary: Chelating agents bind to toxic compounds and are excreted through normal detox pathways; e.g. urination.
Bioremediation & Bacterial Chelation
Several species of bacteria have demonstrated the ability to bond with toxic elements in ways similar to compounds like EDTA. There are two conceptual approaches to bioremediation: absorbing the toxins and transporting the waste (ex situ) and absorbing the compounds and transforming them to a non-toxic compound (in situ).
There’s no line in the sand where natural ecological balance stops and bioremediation begins. Planting extra trees to help reduce carbon dioxide isn’t likely to be considered “bioremediation” but using sodium hydroxide air scrubbers to do the same might be. Environmental impact of a bioremediative compound is of particular interest in cases where containment is an issue. For example, using bacteria to absorb spilled oil in open waters.
Bacteria are a part of life—be it in our digestive tracts, on our skin, in the air, or out in the world. Throw a rock in any direction and you’ll probably hit a few species that would soak up toxins to some degree. An interesting discussion on the discovery of bioremediative bacterial compounds and there related properties can be found here. For discussion’s sake; let’s agree that 1.) there’s a lot out there, and 2.) those found in the human digestive tract are really interesting to ponder on.
Quick Summary: Certain bacterial species can bind to toxins.
Chelating Bacteria Found in Humans
Sounds like a headline you might read on a biology news site right? Believe it or not, human-gut-colonizing bacteria showing toxin-chelating properties isn’t news. There’s a host of bacteria that are used in industrial applications of removing toxins from the environment that can also be found in the human gut. Many such strains are known to be pathogenic and contribute to poor digestive conditions and other health concerns. Among these bacteria are Citrobacter fruendii, Klebsiella pneumonia, Escherichia coli, and Klebsiella oxytoca (R). Some examples of probiotic bacteria acting as sorbents for heavy metals:
- Lactobacillus rhamnosus (LC-705) binds to cadmium and lead in aqueous solutions (R)
- Lactobacillus paracasei subsp. paracasei (NTU 101) and Lactobacillus plantarum (NTU 102) remove iron (R)
- Bifidobacterium longum (BB79) absorbs lead in animal models (R)
- Lactobacillus rheutari strains remove lead and cadmium from drinking water (R)
The methodology of measuring the chelating potential of human-colonizing bacteria is as such: introduce toxins to an in vitro model and see if they influence absorption rates. In the past, this hasn’t been a very accurate model due to the disparity between actual GI conditions and testing models. More recent models, such as SHIME more accurately simulate GI conditions. More novel bacteria reduce the overall measurable amounts of toxins after ingestion (or simulated ingestion in the case of most research.)
Heavy metals damage our bodies, largely, by their impact on cellular structures. Probiotic bacteria, being cellular organisms themselves, are wholly susceptible to such toxic damage. To face this, Mother Nature has evolved certain probiotic species with countermeasures. These countermeasures, such as the binding of metals to the outer membrane wall, is pivotal in their role as chelating agents. Once bound, the toxins are eliminated through normal defecation. Keywords here are heavy metal resistance (in the context of bacteria) for those looking for a deeper dive.
Quick Summary: Certain probiotic bacteria bind to toxic metals and pooping removes them.
The binding of heavy metals to cellular walls of bacteria in such a way that facilitates their ready elimination is great. It turns out that certain metallic compounds that bind to these walls can also have disruptive effects that reduce the ability of certain bacteria colonies to grown normally.
One such case is illustrated by Titanium Oxides (TiO2) normal autolysis process among probiotic bacteria Bacillus subtilus such that measurable counts were much higher than those unexposed. What that means is that nanoparticulate binding among bacteria could greatly impact their normal life/death cycles and resulting enzymatic signaling (R). This could result in pathogenic bacteria that just seem like they don’t want to die.
Quick Summary: Toxic metals could cause pathogenic bacteria to stick around a lot longer than normal.
Bacteria play an integral role in regulating human biological processes. Whether that’s synthesizing vitamins, contributing to respiratory infections, or removing toxic heavy metals all depends on the bacteria. So-called “probiotic” bacteria are renowned for offering beneficial support to gastrointestinal health. The fact that many of these bacteria are known to absorb toxic metals is no real surprise. After all, guarding against cellular damage to the GI tract is promoting better gut health, right?
There’s no argument here to substitute clinically-proven chelation therapies such as EDTA in the face of toxic exposures. There’s simply interest and hope that not only will Science continue to help us better understand the role of bacteria in our lives but that it will also continue to offer much more specific applications.