Dataset from: Changes in cell size and shape during 50,000 generations of experimental evolution with Escherichia coli

Bacteria adopt a wide variety of sizes and shapes, with many species
exhibiting stereotypical morphologies. How morphology changes, and over
what timescales, is less clear. Previous work examining cell morphology in
an experiment with Escherichia coli showed that
populations evolved larger cells and, in some cases, cells that were less
rod-like. That experiment has now run for over two more decades.
Meanwhile, genome sequence data are available for these populations, and
new computational methods enable high-throughput microscopic analyses. In
this study, we measured stationary-phase cell volumes for the ancestor and
12 populations at 2,000, 10,000, and 50,000 generations, including
measurements during exponential growth at the last time point. We measured
the distribution of cell volumes for each sample using a Coulter counter
and microscopy, the latter of which also provided data on cell shape. Our
data confirm the trend toward larger cells while also revealing
substantial variation in size and shape across replicate populations. Most
populations first evolved wider cells but later reverted to the
ancestral length-to-width ratio. All but one population evolved mutations
in rod shape maintenance genes. We also observed many ghost-like cells in
the only population that evolved the novel ability to grow on citrate,
supporting the hypothesis that this lineage struggles with maintaining
balanced growth. Lastly, we show that cell size and fitness
remain correlated across 50,000 generations. Our results suggest that
larger cells are beneficial in the experimental environment, while the
reversion toward ancestral length-to-width ratios suggests partial
compensation for the less favorable surface area-to-volume ratios of the
evolved cells.