The defense of Konrad Gras was drawing near, but nobody was worried. Even Johan Elf, who is usually juggling a delicate balance of tranquilizers and caffeine when his PhD students are about to graduate, remained unusually appeased. Konrads radiating calm and air of I’ve-got-the-situation-under-control was contagious. So it happened that the nervous atmosphere that usually characterizes the lecture hall before a PhD defense was all but missing this particular December morning. The opponent, Prof. Paul Wiggins from Washington University, opened the session with a fun and educational introduction to the field. Konrad followed suit with a summary of his work that left nothing to chance, carefully guiding the audience through the complex concepts of his thesis. The subsequent questioning was rather a discussion between two peers than an examination, and Prof. Wiggins was notably excited about some of the concepts Konrad presented. When the time came for the committé to cross-examine the respondent, Prof. Camilla Björkegren made sure that Konrad knew his chromosome dynamics, and Prof. Thomas Schön tested his attention to detail, particularly concerning the many errors notoriously plaguing pioneering research projects like this. Hans Blom’s concerns about the lab website were unclear to most of us, but Konrad answered this question too with flying colors, another testimony to his composed nature. Konrad’s failure to draw 1,000 straight lines on the blackboard will not be held against him.

When the committé withdrew to deliberate their decision (aka drink Sherry and compare science) we enjoyed hearty pies and deserts prepared by Konrad´s mother. Still, nobody was worried, a feeling that would remain well into the night at Kalmars Nation where we enjoyed the first “proper” dissertation party since the pandemic hit in 2020. I hadn’t realized how much I missed them.

In his thesis, Konrad explores the dynamic organization of the Escherichia coli chromosome. During the cell cycle, the genetic material undergoes significant reorganizations to facilitate essential processes like DNA replication and chromosome segregation and ensure that each daughter cell inherits a complete copy of the genetic material.

Using fluorescence microscopy, Konrad tracked the dynamics and positioning of chromosomal loci in living bacteria. By labeling a specific chromosomal locus and a replisome subunit in the same cell, he observed that as loci were replicated, their movement slowed momentarily. The data revealed that the chromosome repositioned itself towards the replisome during DNA replication and not vice versa, which has also been suggested.

To study the three-dimensional (3D) positioning of chromosomal DNA, Konrad used a neural network-based algorithm to determine the 3D coordinates of fluorescently labeled loci. Time-lapse imaging of an 83-member library of E. coli strains with different locus labels allowed him to map the 3D localization patterns of multiple chromosomal loci throughout the cell cycle. The data revealed new radial localization patterns and confirmed known longitudinal chromosome reorganization. Finally, he used the experimental data to inform a polymer model of the chromosome to help explain how large chromosomal domains (megabase-sized) form and reorganize dynamically during the cell cycle.

Read Konrads’s thesis here