Scientists at UC San Diego have found a surprising role for DNA in cell formation. According to findings, published last week in the journal Cell, DNA plays an architectural role in shaping bacterial cells through an action that could be described as “pumping up” the cell.
The researchers made their discovery using time-lapse fluorescent microscopy to methodically track cell formation in Bacillus subtilis through the sporulation process, in which the cells split into a mother cell and a smaller cell called a forespore. Using cryo-electron tomography, they captured extreme close-ups of the process as it progressed and observed the mother cells inflating the forespore with DNA to stretch out the cell.
"Biologists tend to think of cell growth as following normal, biosynthetic pathways, but we found a pathway that is not normal, as it does not depend on processes normally required for growth," said Pogliano, a professor in the Section of Molecular Biology and the paper's senior author. "All you need for this cell to grow is to inflate it with DNA and its associated positively charged ions, and the ability to make more membrane so the cell can get bigger. Nothing else seems to be required."
These findings offer evidence that DNA plays more roles than just that of encoding genetic information and may have relevance to the shaping of human cells. The researchers also believe the results may offer clues as to how cellular life originated—before bacteria had methods to control their internal pressure, DNA’s role in inflating cells may have been helpful.
Image: Cryo-electron tomography images of a forespore inflated by DNA (left) and of a deflated forespore in the absence of DNA (right). The membranes are highlighted in pink and purple. Image courtesy of UC San Diego.