Nate Cermak – Measuring growth, size and macromolecular changes in single bacteria

One of the most basic and fundamental functions of environmental microbes is that they accumulate material during growth – in fact, this may be the simplest definition of growth. While this process is relatively easily studied for culturable isolates, due to the technical challenges involved, very little is known about the growth of uncultivated marine microbes in their native low-nutrient environments. As these microbes are drivers of large-scale biogeochemistry, we are very interested in being able to quantify their growth in situ. I will talk about ongoing work to directly measure the growth rates of marine microbes in both their native and nutrient-supplemented seawater. Additionally, the biophysical correlates of growth (cell size and macromolecular composition) are still only somewhat understood. In E. coli, we show a way to measure both dry mass and a rough index of macromolecular composition, and how these properties vary as a function of growth. Potential future directions include coupling these measurements with single-cell genomics of uncultivated marine microbes.