Streptomyces

by Anne A. Madden

I hate visiting the doctor’s office. I hate the harsh fluorescent lighting, I hate the sound of the crinkly paper on the examination benches, and I hate the stomach knots I get when a nurse takes my blood pressure. Inexplicably, I always feel like I’m about to fail a test for which I forgot to study. Most of all, I hate that I have to go because I’m suffering from an infection. With joints aching, tonsils swollen, or blisters weeping, I’ve ended up at various doctor’s offices throughout my life—prodded, swabbed, and punctured—as clinicians tell me I have various infections caused by germs.

Germs. The very word inspires an itchy feeling that only dollops of hand sanitizer can relieve. Maybe I don’t actually hate doctor’s offices, maybe I just hate the germs that forced me there.

These germs are out get me. I’m convinced. They throttle my throat with Strep in the fall; they wedge my head in a vice with a sinus infection every winter; they force my road burns to weep pus every spring; they wrench my ears with ‘swimmer’s ear’ every summer. I hate germs. I hate them so much I decided to make a career out of killing them.

My first job out of college was as a microbiologist at a company that discovered and developed new antibiotics. I started working there to rid the world of those germs that had caused me so much pain. Ok, I also started working to pay rent, but the added bonus was that I would retaliate against germs. Vengeance would be mine!

On my first day of work, I buttoned up my lab coat, pinned my hair back, and snapped on my latex gloves. Imagine my surprise when I walked through the laboratory doors and learned that my hardworking colleagues were not just fellow scientists, but a group of germs themselves: Streptomyces.

At first glance, Streptomyces seemed more pathetic than noteworthy. Peering over into their petri dish cubicles, I learned they don’t usually cause disease, they can’t move on their own, and they’re remarkably common all over the world. They seem to lack both distinguishing features and ambition. Their role in nature is not even particularly glamorous. Streptomyces are decomposers; they hang out among dead things. For evidence of their existence, smell fresh-turned soil. That warm, ‘earthy’ smell is predominantly geosmin, one of the many chemicals Streptomyces produce while grazing on plant matter.

What makes Streptomyces special, it turns out, is not rarity, an affinity for an unusual habitat, a novel environmental role, or even how many people they kill each year. Rather, Streptomyces are unique because of how many people they save each year.

Sixty percent of the antibiotics we use today—those chemicals responsible for killing disease-causing bacteria—are produced by Streptomyces. They evolved these compounds to defend their food, dead stuff, from other bacteria. But we humans have co-opted these compounds for our own defense. Most of the tablets, pills, and syrups I had gagged down over the years to fight infections, were the result of their labors.

In the laboratory, I was working to grow these bacteria and to coax from them ever more useful compounds. In the lab, the Streptomyces oozed antibiotics of vibrant colors; from brilliant crimsons, pale corals, and buttery yellows, to midnight blues, vivid scarlets, and burnt umbers. These chemicals are not only aesthetically beautiful, but structurally exquisite as well. They are the microscopic great pyramids; they are miniature Eiffel towers—structural and aesthetic wonders of the infinitesimally small world. Amazingly, these compounds are so complex that for the most part we have not figured out how to build them. Instead, we just farm Streptomyces bacteria to build them for us.

Yes, humans can fly to the moon, clone life, and instantly have a conversation across the globe, but when we get sick, we still require microscopic Streptomyces to save our lives.

My quest to destroy all germs seemed to have faced a hiccup. By determining all germs to be evil, I may have been somewhat unfair. But I swear I’m not alone in this misunderstanding. Streptomyces decidedly lack a public relations advocate.

Streptomyces have toiled away in many labs without praise or even public credit for years. Most children, like me, grow up knowing milk comes from cows, and eggs come from chickens. Yet adults don’t know where antibiotics come from, even though said antibiotics are prescribed to 4 out of 5 Americans every year.

My guilt increased as I learned that Streptomyces were not just daily saving the lives of humans and domesticated animals such as cows and pigs, but also wild animals and plants as well. It is this latter relationship with the wild species that is most ancient. While humans discovered Streptomyces antibiotics nearly a hundred years ago, some insects discovered them millions of years ago.

One such clever beast is the beewolf. The beewolf is a wasp that lives a solitary life hunting bees, drinking nectar, and making baby beewolfs. The mother beewolf will dig a hole in the ground and drop off her baby with a packet of food—then she leaves forever. Such a parenting strategy appears quite risky, if not somewhat abusive, as predatory fungi are waiting around soil granules to feast upon the vulnerable offspring.

To protect her young from this fate, the mother wasp coats her baby with Streptomyces living in tiny pockets of her antennae. Having slathered on the milky lotion of bacteria, she abandons her baby with these microscopic guardians. Before the deadly fungi can attack, the Streptomyces defend the beewolf babies with toxic chemicals. The young wasp is kept safe as it develops into an adult, cloaked in an earthy bacterial gown.

While humans and beewolfs have co-opted the chemical machinery of Streptomyces, plants have taken their protective powers one step further. Many plants harbor Streptomyces in their roots, where they kill pathogens of the plants.

Back at my lab, where I now study the diverse bacteria living with social wasps, I can feel the tingling of another sore throat coming on. I remain a bit bitter that trillions of germs make it their life’s work to punch holes in my tissue. I want vengeance, but I know now that such vengeance, when it is truly necessary, is best meted out not by me but by other bacteria, the Streptomyces. Those boring, dirty, decay mongers are who we depend on for our own antibiotic cloak , a cloak we are dosed with not by our mothers but instead by doctors, a cloak on which we depend for survival in a world filled with pathogens, a cloak that needs to be worn sparingly and honored lovingly. Whether we acknowledge it or not, many of us owe our lives to this cloak, produced by bacteria that most of us do not even know exist.

References

Aminov RI. 2010. A brief history of the antibiotic era: lessons learned and challenges for the future. Frontiers in Microbiology. Doi: 10.3389/fmicb.2010.00134.

Kaltenpoth M, Goettler W, Herzner G, Strohm E. 2005. Symbiotic bacteria protect wasp larvae from fungal infestation. Current Biology. 15:475-479.

Mahajan GB, Balachandran L. 2012. Antibacterial agents from actinomycetes – a review. Front Biosci. 4:240-253.

Tarkka MT, Lehr N, Hampp R, Schrey SD. 2008. Plant behavior upon contact with Streptomycetes. Plant Signaling and Behavior. 3(11): 917-919.

US Centers for Disease Control & Prevention: http://www.cdc.gov/

About the Author

Anne A. Madden received her Ph.D. in biology at Tufts University, and is a microbial explorer by training. Her research focuses on characterizing microbial communities associated with arthropods (bugs). Her recent studies have involved the microbial jungles associated with paper wasps. Prior to her graduate work, she was a microbiologist at a pharmaceutical company where she developed novel antibiotics from previously uncultured bacteria. She tweets at @AnneAMadden.