Of Bacteria, Weeds and Drug Resistance
When I first learned about Darwin’s theory (sic) of natural selection many years ago it was an abstraction to me. This largely resulted from the way it was taught back then—mostly as a theory with no firm basis in reality (at least a reality that I could understand at the time). Finally, after taking a bacterial genetics course as an undergraduate microbiology major—and experiencing firsthand (in the laboratory) the selective pressures that result in the emergence of bacterial antibiotic resistance—Darwin’s theory became a crystal-clear, concept for me. With this in mind, the epidemic of multiple drug resistant strains of bacteria that resulted from the rampant overuse of antibiotics in medically settings and as feed additives over the past is a great Having said that, what do bacteria and weeds have to do with one another?
First, both grow rapidly. Second, if left unchecked, their growth can wreak havoc and cause substantial damage to humans. Finally, and perhaps most importantly, both are capable of mutating rapidly in response to selective pressures. To that end, there was an interesting article in today’s NY Times detailing the emergence of “Roundup” resistance species of weeds e.g. pigweed, in the US, Brazil and Asia.
For those of you not familiar with the Roundup story, about 20 years ago scientists at Monsanto discovered the gene (and its protein) that renders plants susceptible to the effects of glycophosate herbicides like Roundup. Recognizing an opportunity, Monsanto scientists genetically-altered the gene and introduced it into various seed crops including soybeans, corn and cotton. Plants grown from seeds that contain altered glycophosate genes are resistant to the herbicidal effect of Roundup.
This innovation allowed farmers for the past 20 years to spray millions of acres of Roundup-ready crops with glycophosate; killing the weeds while leaving the soybean, corn and cotton plants unharmed. Also, glycophosate is not toxic for humans and breaks down quickly; making it environmentally friendly and a cost effective treatment. Not surprisingly, the financial savings of RoundUp-ready crops caused sales to explode in the late 1990s shortly after the seeds were introduced. Today, Round Up-ready crops represent about 90% of the soybeans and 70% of the corn and cotton annually grown in the US.
Segueing back to antibiotics, shortly after the introduction of penicillin and streptomycin in the late 1940s and early 1950s, a small number of prescient microbiologists warned that indiscriminate use of these drugs would likely result in the emergence of antibiotic resistant strains of bacteria. This, in turn, would render these antibiotics therapeutically ineffective. While there was little laboratory evidence at the time to substantiate or refute these claims the predictions made by these scientists relied almost exclusively on Darwin’s immutable laws of natural selection.
Because the newly-discovered antibiotics were extremely effective and easy to use, the medical establishment, animal feed industry and the US Food and Drug Administration chose to ignore the warnings for over 30 years or more. Unfortunately this culminated in the ongoing pandemic of multiple antibiotic resistant bacteria that began in earnest in the mid 1990s.
Likewise, shortly after the introduction of RoundUp-ready seeds, some forward-thinking crop scientists suggested that it may only be a matter of time before RoundUp-resistant weeds would appear. Again, despite lessons learned from the overuse of antibiotics Monsanto officials quickly convinced farmers and US regulators that the emergence of RoundUp-resistant weeds was unlikely. According to the Times article, today, approximately 7 to 10 million acres of corn, soybean and cotton (out of about 170 million acres) are afflicted with RoundUp-resistant weeds. Like their antibiotic resistant bacterial cousins, RoundUp-resistant weeds are fast-growers, hardy and require a combination of toxic and environmentally damaging herbicides to eradicate. While Monsanto is trying to downplay the significance of the appearance of RoundUp-resistant weeds, the company has taken an unprecedented and extraordinary move by subsidizing cotton farmers’ purchases of competing herbicides to kill the resistant weeds.
Despite assertions to the contrary, it is hard for me to believe that Monsanto scientists excluded the likelihood that RoundUp-resistant weeds would eventually appear. To that end, Monsanto and other companies have already developed genetically-engineered crops that are resistant to other herbicides. This, coupled with the financial subsidies to purchase competitor’s herbicides suggests that RoundUp-resistant weeds may be more prevalent than reported and that American farmers may only be experiencing the veritable “tip of the iceberg.” To learn where RoundUp is no longer effective in controlling weed growth in the US, please click here.
Similar to many of the recommendations designed to reduce the incidence of multiple drug resistant bacteria, crop scientists are urging farmers to use more than one herbicide to eradicate Round-Up resistant weeds. This recommendation prompted one cotton farmer to quip “If we have to add another product with the RoundUp to kill weeds. Why are we buying and planting RoundUp-ready products?” Good question!
I think the emergence of RoundUp-resistant weeds is another example of companies placing profits before good science and rationale thinking. In the case of RoundUp resistance weeds it was never a question of “if” but when! I think even a rocket scientist would have known that!
I gotta give it up for Darwin; he was one smart and insightful dude!
Until next time…
Good Luck and Do Good Science!!!!!!!
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rush of energy simply by getting a whiff of freshly-brewed joe? If you do, there may be a genetic explanation for it.