DNA in the Clouds

As a third year graduate student in a biochemistry lab, I don’t often get experiences like this. A giant wave-generating tank is novel to me and quite a bit different than the pipet-land I usually live in. Walking into the transformed hydraulics lab always leaves an impression on me. The facility has come alive. It is crammed full with buzzing whirring equipment, and buzzing, whirring people. Scientists and students from all over the country all pointed at a common goal. Every time I walk in there, I step back and really understand what I am a part of. I’m proud. This experience hasn’t always been easy, but it has been rewarding. Certainly, the unwavering dedication of everyone down at the waveflume day to day is truly inspiring.

I am not the only biochemist/biologist involved in IMPACT, but definitely my work stands apart from what others are doing. The name of my game is DNA. My efforts are to collect cells from the waveflume and extract their DNA, which will then be used to identify all the species present.   I would like to characterize not only what microbes are there, but also how they change across a bloom and relate to a natural ocean phytoplankton bloom. More specifically, I am interested to learn which species transfer from bulk to the sea surface to aerosols (airborne particles) and how this changes in conjunction with the growth of phytoplankton and correspondingly bacteria. My highest hope is that certain phenomenon, like ice nuclei, particle types, and interesting organic molecules, might be able to be connected to the predominance of a species or group at the time of their occurrence.

To do this I collect water samples. Harvesting cells is done by vacuum filtration under sterile conditions serially with different sized filters to fractionate the samples into phytoplankton, bacteria, and viruses and vesicles. The major hurdle to my sampling is having enough. Cells are not overly abundant in the marine environment and many liters of water are generally required for DNA analysis. Here we are trying to optimize our methods so that that we get as much DNA from minimal sample amounts so that other analyses are not disrupted. Additionally, sampling cells from aerosols poses its separate challenges. We are using a SpinCon PAS 450-10A Wet Cyclone Portable Air Samplers (Sceptor Industries, Kansas City, MO) to concentrate cells in the aerosols. This instrument has previously been used to sample air above a NY city high-rise and other sites for microbes. The instrument pumps aerosols into a glass chamber containing buffer creating a vortex in which cells are trapped which then are collected by our standard methods. DNA is isolated using an optimized phenol chloroform extraction. Then our precious samples will be sent away for sequencing to identify species.

Yesterday was big sample collection day for me. Lots of filtration. Today, I am extracting DNA from the aerosol samples. I hope they have lots!

Jennifer Michaud, Graduate Student, Burkart Group, Department of Chemistry and Biochemistry, UC San Diego