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Ralph Seelke: Remembering a Treasured Colleague

Ann Gauger
Photo credit: ANIRUDH via Unsplash.

Editor’s note: Dr. Ralph Walter Seelke passed away on December 30, 2021.

Dear Ralph,

It was a pleasure and an honor to know you. I was saddened to hear of your passing last December, but from what I read of the circumstances, you were doing what you loved when it happened— you had a heart attack while cross-country skiing with friends. Unfortunately, I didn’t find out until I googled your name. There is a whole community of scientists who will mourn you now that they know.

From your obituary:

Ralph pursued graduate studies at the University of Minnesota and the Mayo Graduate School of Medicine, finishing his work for a PhD in microbiology in 1981 and staying at Mayo for postdoctoral work until 1983. He was a professor at various places after that and at the University of Wisconsin in Superior from 1989 until his retirement in 2014. In retirement, he taught in a service capacity for several semesters in China, Kenya, and Ethiopia, which was fulfilling work for him. Ralph and Julie raised three children together, and Ralph devoted his free time to both family and Christian service. He often said that following Jesus is the “organizing principle” of life. 

Our Work Together

I first met you at a conference where you presented a paper on your experiment in long-term-evolution, or LTE. A few years later we collaborated on a project that had come to light during your work on LTE. You had been culturing a strain of bacteria that had been carrying two mutations in its trpB gene, and could no longer make tryptophan. Two new mutations could have easily reverted X and Y, by following a step-wise selectable path. One mutation, call it X, had a strong effect. It knocked out trpB function completely. The second mutation, Y, only partially reduced trpB function. When trpB had both X and Y mutations, the cells couldn’t grow. But if X reverted back to its original amino acid, then the cells could grow slowly, and eventually there should have been a reversion of Y, and the trpB gene would be restored to wild type function.

Surprisingly, that never happened, though you had cultured a trillion cells. The hunt was on to determine why. What we found was something we should have realized. Cells are not focused on getting a particular mutation. Mutations occur independently of the needs of the organism. This is standard evolutionary stuff. But what that means is mutations to X can occur anywhere in the gene. In fact, they can mutate nearly everywhere else first. 

We sequenced the trpB gene and its neighborhood and found there were numerous mutations that turned off the trpB gene completely. There were insertions, deletions, and rearrangements in the gene and in its promoter region. All of them stopped the gene from being transcribed. And that was the key.

The trpB gene was in a plasmid that churned out a lot of trpB transcript. The transcript was then translated into trpB protein by the cells, but remember, the trpB gene was broken to start with. All that protein was useless to the cells, and making it was costly. So, any cell that had a mutation that turned off transcription would have an advantage compared to its sister cells. It would no longer be making useless protein and could use the energy to grow and reproduce faster. Let’s call the new kind of cell Z. Z cells would take over the culture and prevent any further evolution of the trpB gene to its wildtype function. There was no longer a step-wise path where each step improved trpB function, because the Z mutation had turned off expression, and you can’t select for a protein that isn’t there.

Exploring Evolution

Our paper demonstrated that when the cost of expression was high, any mutation that turned off expression would come to dominate the culture. The paper was published in BIO-Complexity.

You also co-authored the textbook Explore Evolution: The Arguments For and Against Neo-Darwinism, testified at the Kansas State Board of Education hearings on evolution, and spoke on the subject of evolution and intelligent design numerous times and in many formats.

You had a gentle smile and a humble disposition. I think you probably had a good sense of humor, also. Anyone who knew you realized your deep devotion to your family and your faith. I will pray for peace, comfort, and grace for them as they grieve.

May the God of mercy and kindness bless you and keep you with him forever.