Dual Label Stable Isotope Incubations Followed By Single Cell Nanosims Analyses To Investigate Microscale Phototroph-Heterotroph Interactions

Tuesday, 15 December 2015: 16:45
2008 (Moscone West)
Xavier Mayali1, Ty J Samo1, Daniel Nilson1, Nestor Arandia Gorostidi2, Laura alonso Saez3, Xose Anxelu Moran4 and Peter K Weber1, (1)Lawrence Livermore National Laboratory, Livermore, CA, United States, (2)Oceanographic Center of Gijón, Gijón, Spain, (3)Fundación AZTI, Sukarrieta, Spain, (4)King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
In natural ecosystems such as lakes and oceans as well as human-engineered systems for sunlight-regulated biomass production (such as algal biofuel ponds), the interaction between autotrophic and heterotrophic processes are critical to determine whether such systems are net autotrophic or heterotrophic. Traditional methods to quantify autotrophy and heterotrophy include primary productivity and bacterial production measurements using radiolabeled substrates that quantify these processes on the bulk scale. To examine the microscale interactions between individual autotrophic and heterotrophic cells, we incubate mixed microbial assemblages with 13C-bicarbonate and 15N-leucine to label individual autotrophs and heterotrophs, respectively. We use nano imaging secondary ion mass spectrometry (with a Cameca NanoSIMS 50) to quantify the incorporation of the rare isotopes by single cells. We will present results from experiments examining the impact of warming on the exchange of C and N between algal and bacterial cells from the coastal Atlantic Ocean, which suggest that increased temperature may strengthen physical interactions and exchange. We will also present data from experiments examining the influence of attached bacteria on the cell-specific inorganic carbon fixation rates of biofuel-producing algal cultures which suggest that certain algal-attached bacterial groups grow faster than when free-living and influence algal growth. We conclude that the examination of individual cells uncover interactions that would be difficult, if not impossible, to investigate with bulk methods.