Because my project this summer involves the use of C. elegans nematodes, much of my usual day involves designing and calibrating worm experiments and protocols. Because neither my mentor nor I have ever cultivated worms, it has taken much time to figure out how to most effectively grow them and utilize them for bacterial conjugation experiments. For example, we must transfer worms between plates periodically so that they constantly have enough bacterial food to eat—this is obviously quite different than the cultivation of microbes like S. cerevisiae or E. coli. Single worms can also be isolated by using a fine-tipped “worm picker” with the aid of a dissecting light microscope, however this is much more tedious than we previously thought and has required a lot of practice. We are currently testing protocols for worm synchronization (the creation of same-age worms by isolating worm eggs using household bleach), the isolation of gut bacteria (by grinding up the worms and plating the results onto selective media), and the use of a microfluidic chip to conduct long-term conjugation experiments.
Although much of my days are filled with worm-related activities, my project will ultimately involve studying the bacteria with which I have infected the worms. In order to measure the rate of conjugation among these bacteria, there must be some way to quantify the cells that are recipients of conjugated DNA. And to make this data robust, we must be able to do this without killing the nematode host (due to grinding). As a result, we have been designing a fluorescence construct capable of predicting cell densities of particular cell populations (conjugation donor and recipient), which we assign each a unique fluorescent color. This has required quite a bit of calibration of the fluorescent protein-detecting light microscope we are using, and this has filled much of the past week.
