Harvard postdoc Tanja Bosak brings together genomics and geology and along the way has learned to deal with differences in research culture.
Robin Orwant
At a recent microbiology conference at Tufts, Harvard postdoctoral fellow Tanja Bosak presented unpublished work on chemicals in rocks that were produced by ancient soil microbes. Researchers don’t know why microbes produced these compounds, but if they could find out, they might gain insight into conditions on Earth over three billion years ago, Bosak said in her presentation. The response from the audience of microbiologists was lukewarm at best.
Soon after, when MIT earth scientist Roger Summons heard about those same results, he was more enthusiastic. “If confirmed, that would be a great coup,” Summons said.
Geobiologist Tanja Bosak uses the tools of molecular biology to answer questions in earth science.
These very different reactions are emblematic of the challenges Bosak faces as she tries to bridge the chasm separating two disciplines—geology and microbial genetics—that until recently haven’t had much to do with one another. Bosak is applying the techniques of cell and molecular biology to the problems in earth science and, in doing so, is blazing trails and attracting attention.
But scientists in each realm have their own ideas about which questions are most worthy of scientific inquiry and what constitutes solid data and reasonable interpretations. Bosak, whose background is in earth science, has experienced firsthand the culture clashes between the two disciplines. The reality of the cultural divide hit home when she began presenting her work to microbial geneticists. “At first, I found it really intimidating,” she says.
Travel back in time
Bosak studies a type of “molecular fossil” called terpenoids: certain fats produced by ancient organisms and found in many rocks around the world, including some of Earth’s oldest rocks. Knowing that certain species of organisms chemically modify terpenoids in characteristic ways, researchers can look for terpenoids with those chemical modifications in rocks of known ages and speculate on the kinds of organisms that were alive at that time, and hence what the environmental conditions might have been like.
But to unlock those mysteries, researchers must first find modern-day terpenoid-producing organisms that they can easily work with in the lab. And they have to figure out what environmental cues induce terpenoid production and, most importantly, what functions the compounds serve.
This has not been easy. The microbial species that produced these molecules died off ages ago. Many of their modern-day descendants can’t be cultured in the lab. “There are no genetic systems for most terpenoid-producing organisms,” says Bosak. “The tools just aren’t there.”
In 2006, Bosak started a postdoctoral fellowship at Harvard that has allowed her to use the tools of molecular biology to learn more about these compounds. She was one of the first postdocs funded by Harvard’s Microbial Sciences Initiative, which seeks to foster interdisciplinary research by linking microbiology with a broad range of fields.
Working with bacteriologist Richard Losick and earth scientist Ann Pearson, both at Harvard, Bosak has found an organism that not only produces a type of terpenoid under normal conditions but also is genetically well characterized and easily cultured and manipulated in the lab: Bacillus subtilis, a soil bacterium.
Using standard molecular biology and biochemical techniques, Bosak, in unpublished work, has even identified a function for these compounds: protecting bacteria from a specific type of environmental stress. Bosak says that this stressful condition may have been present when the compounds were produced over three billion years ago and that this finding could help researchers better understand how and when certain forms of microbial life evolved on Earth.
Between borders
When Bosak presented these results at the Boston Bacterial Meeting in June, several skeptical microbiologists in the audience quietly grumbled that she was trying to rewrite history based on very few data. They said that the terpenoids could have more than one function and there’s no guarantee that the compounds did the same job in ancient microbes as they do in modern ones.
Bosak doesn’t deny the limitations of her findings. But now, geobiologists at least have somewhere to start. “We can make more informed extrapolations,” she says.
This kind of speculation doesn’t sit well with bacterial geneticists accustomed to more evidence and fewer leaps in logic. But it’s routine in earth science. “In earth history, you’re inherently limited,” says Bosak’s former graduate advisor, Dianne Newman, a geobiologist who recently moved from Caltech to MIT’s biology department. “It isn’t as if you can go back in time and do the experiment. The best you can do is come up with a theory.”
This cultural difference can lead to conflicts. “I’ve personally struggled with this a lot,” says Newman.
Still, Bosak’s work is earning accolades. This fall, just a couple of years after receiving her Ph.D., she will take up her new position as assistant professor in MIT’s Earth, Atmospheric and Planetary Sciences Department.
“Those, like Tanja, who can bridge genomics and geology will reap huge rewards,” says Summons. “I am in no doubt about that.”