As I’ve written before in this space, weeds are just plants where we don’t want them. A well-mannered garden plant can become a weed merely by growing in the wrong part of the garden. I shouldn’t complain too much as I enjoy weeding. Therapeutic or not, weeding is time consuming and if you wait too long it can harm the plants you’re trying to grow. For larger farms this labor becomes significant. According to a study by Karen Klonsky from UC Davis in the American Journal of Agricultural Economics (2011) organic weed control (including mulching and hoeing) can be more than twice the expense of the chemical treatments available for commercial tomato production.
With this in mind, it’s easy to see why many farmers would gladly embrace herbicides. Glyphosate was introduced in the seventies by the company that must not be named. It was given the name “round-up” presumably to evoke visions of cowboys and herds of cattle. Yee-ha.
Glyphosate inhibits an enzyme that plants need to live. Enzymes are protein catalysts. That is, they help a chemical reaction to occur without being consumed in the process (that’s always made me wonder whether party catalysts are they actually partying). The enzyme that glyphosate inhibits occurs in plants but not in animals: it helps make certain amino acids. For the most part, enzymes only operate on their correct target molecules: their substrates. A very carefully structured molecule can sometimes stick to the active part of an enzyme and gum up the works. That’s how glyphosate works.
Because we don’t have the enzyme 5-enolpyruvylshikimate-3-phosphate synthase, we’re not sensitive to glyphosate. But bacteria do have this enzyme and could therefore be sensitive to glyphosate. This is one of the points of a new paper getting a lot of attention these days in the journal Entropy by Anthony Samsel and Stephanie Seneff. It is an interesting point and one well worth testing. Unfortunately the authors (who are not biologists or chemists) do not. Instead they present hypothesis as fact. That’s bad science, or maybe more accurately, not science. The authors assert that this potential toxicity leads to all manner of current ailments from Crohn’s disease to Alzheimer’s.
We should find out whether glyphosate is toxic to gut bacteria. It seems unlikely as the organisms will be able to pick up the amino acids from their environment (our intestines) readily (bacteria are adept at this). One study looked at glyphosate toxicity in forests and found that though microbiota suffer glyphosate toxicity in the laboratory, when they are in the soil they do just fine (Busse et al Soil Biology and Biochemistry 2001).
What is really saddening to me is all of the citations Samsel and Seneff get in social media. I have seen dozens of links to their work on alternative news sites and lots of people treating their hypothesis as fact. They may be right about glyphosate toxicity, and if they are perhaps the stuff should be banned. Whether they’re right or wrong, we won’t know until the real studies have been done. Until then, bad science doesn’t help a good cause.