By: Joseph Maa

Date: 5/25/2017

Why can’t researchers do research and have professors just teach? It’s a natural question that exists at all research institutions, with Berkeley as no exception. It’s a problem that frustrates both students and professors to no end: researchers are increasingly subjected to higher and higher demands on their time, while students are impressed by their professors’ accomplishments and simultaneously frustrated by their inability to teach.

Meet Professor Taga. Well known for uncovering the biosynthesis pathway of the lower ligand of B12, Professor Taga teaches MCB-PMB 148 (cross-listed as a class in both Molecular and Cell Biology and Plant and Microbial Biology) here at Berkeley, Microbial Genomic and Genetics.

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Figure 1: Professor Taga escaped from her desk in the office. (Photo credits: Jim Block)

It’s not common to see professors wield white chalk nowadays, but she is one of a rare few that continues to do so. In an age where biology lectures are synonymous with the feared program Powerpoint, nothing quite catches a student’s eye like a professor who loves the chalkboard. It fosters learning at a reasonable pace as well as a sense of solidarity with students. Its also most certainly slower, but it signified to me a strong passion for teaching and was one of the most memorable traits of the class.

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Figure 2: Hanging out with Professor Taga on the last day of class with Dylan! (PC: Omar Khaled)

Like many of the faculty on campus, Professor’s Taga career in science started early. During her undergraduate years at Carleton College, she was exposed to a few simple experiments in vesicle trafficking. As her curiosity in biology grew, like many of us, her ambitions to elucidate critical health problems became a central focus of her life. Even as an undergraduate, her goals were lofty. She was set on solving cancer, an insane undertaking any way you look at it.

However, fate would take her down another path and after her entry to graduate school at Princeton, during rotations, she quickly found herself at home in Bonnie Bassler’s lab, prominently known for it’s work on how bacteria talk to each other. Rotations are 10 week “trial periods” where the graduate student conducts a small project within a lab, and if both parties have a vested interest in continued work together, is where a graduate student’s career begins. As a compelling speaker, Professor Bassler is known to many as the face of quorum sensing.

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Figure 3: Bonnie Bassler and her quirky personality[1]
Of course, like all scientific careers, Professor Taga’s started off humbly. While working on her small project (this paper here [2]), she tackled the intricacies of working with Salmonella typhimurium. In more ways than one, her tractable genetic model worked well, perhaps a little to well, and she quickly came down with a fever while working with the inscrutable bugs. After a few days of intravenous fluids and antibiotics, she returned to the lab – reenergized and enthusiastic – as only young people could be.

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Figure 4: Salmonella typhimurium at work, ready for infection [3]
After receiving her PhD in Molecular Biology, according to Professor Taga, looking for post-doctoral work was fairly informal, consisting of interviews at a few different labs. What she said to me was that the spirit of the prevailing culture in academia at the time was to “[prove] that [they’re] adventurous and are willing to do something different”. So, she decided to move into post-doctoral work on plant-microbe interactions between Sinorhizobium meliloti and its invasion into alfalfa root nodules in Graham Walker’s lab at MIT. [4]

During her five years at Walker’s lab, she ran over to Chris Walsh’s lab for six months to get into the nitty gritty of enzymology. There, she learned the nuts and bolts of characterizing enzymes from Annaleise R. Howard Jones to figure out the details of BluB, a cannibal enzyme that destroys flavins and was the missing enzyme of benzamidazole biosynthesis in aerobic conditions. Researchers had looked long and far for the missing enzyme, but the mystery was still an open project.

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Figure 5: Graham Walker, Professor Taga’s post-doctoral advisor [5]
While hammering out the details of her soon-to-be-explosive paper, she contacted Nicholas Larsen, an expert in x-ray crystallography and old friend from Carleton, to tease out the physical structure of the enigmatic BluB enzyme.

As a colleague, he had contacted her on multiple occasions with the question, “Do you have a protein for me to crystallize?”

As a result, as soon as she had obtained the purified BluB protein, she shipped it off to him, with the hope she could get a little more insight to the protein that had eluded researchers for so long. On his first attempt to crystallize the protein, he actually got a crystal – through skill or luck, I could not say – but he was instantly hooked on this strange tiny protein.

However, while Larsen tried again and again to replicate his results from the first batch of enzymes, he was foiled time and again. For some reason, the protein evaded his attempts to be crystallized, but he kept at it in hopes that he could solve the puzzle. It just so happened, that on the very last batch of enzymes sent to the Advanced Light Source here at the Lawrence Berkeley National Laboratories, that a structure emerged from the muddled data. The picture was sent to Professor Taga, (who was a post-doc at the time) and the enzyme structure was included on the paper that would launch her career.

And so, like all great scientists, as the last papers were written and final documents signed, she struck off in hopes of finding a new home, a lab to call her own. After a few interviews, Berkeley welcomed her with open arms.

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Figure 6: Image from Hazra’s paper, showing the different precursors of dimethylbenzamidazole under different combinations of genes [6]
As she began to talk about her career thus far, as PI of a lab, we transitioned to a paper by Hazra et al., a recent post-doc of the lab (and currently a professor at IISER – Indian Institute for Science, Education and Research in Pune). [7] The paper covered looking for and identifying candidate genes for benzamidizole biosynthesis under anaerobic conditions, complementing Professor Taga’s discovery of the final enzyme in benzamidazole pathway under aerobic conditions. They showed that a precursor molecule AIR fed into the pathway and used some clever genetics to demonstrate the pathway using mutants. Ultimately, she said their goal was to elucidate how corrinoids are shared and whether they could predict specific corrinoids simply on genome sequence alone, and the structural variability of corrinoid lower ligands.

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Figure 7: Keio mutant diagram and construction [8]
Going back to her roots, she gleefully admitted that she got to contribute benchwork to the project, ordering Keio mutants (an E. coli mutant collection) and making double mutants. From grad-student to post-doc to associate professor, she has come full circle in her scientific career as a teacher and mentor to a new generation of microbiologists.

Thanks to Professor Taga for being open to an interview!

Your friend,

Joseph

 

 

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