Kevin Richberg


My research focuses is on the major microbial players involved in subsurface biomass production at deep sea hydrothermal vents.  My advisor, Stefan Sievert, and I are attempting to better understand the carbon cycling that forms the base of the vent ecosystem food chain.  The more we can learn about the organisms doing the majority of the carbon fixation in these environments, the better understanding we'll have of how the entire system exists without any energetic input from solar sources (the world living without light).

The experiments we designed to help us identify carbon fixing microbes involve two major techniques that both use the same labeling system.  After recovering hydrothermal fluid from two diffuse flow vent sites in the 9 degree North hydrothermal vent field, I incubated them for several days with heavy carbon compounds (13C bicarbonate and 13C methane).  Following incubation the microbial cells were collected either in filters or preserved in suspensions.  A technique called Stable Isotope Probing (SIP) will be used on the filtered material (after DNA extraction) to separate "heavy" autotrophic DNA from "light" heterotrophic DNA.  With this DNA we can examine specific genes involved in the carbon fixation process.  A second technique to be used on the preserved cells is nano-scale Secondary Ion Mass Spectrometry (nano-SIMS).  With the nano-SIMS machine we can identify cells of specific types (with 16S DNA probes) and see if they incorporated the heavy 13C label and to what extent.

Ultimately it is the goal of this project to gather as much identifying data as possible about the microbes growing under our different incubation conditions.  With this genetic and phylogenetic information we will be able to better infer how the sub-seafloor biosphere functions, and what new experiments can be designed to capture more data.