New Applications of Proteomics Informs Microbial Functions in Soils.

Within terrestrial systems, microorganism play fundamental roles as drivers of terrestrial carbon fluxes via either the release of carbon to the atmosphere or sequestration of the carbon in biologically inactive forms.  These microbes do not live in isolation, and as such understanding the function of the microbe within the context of the community is critical to the characterization of the community as a whole.  Protein expression profiles reveal the actual functional potential of any biological system, but obtaining this information from the biological matter in soil can be challenging.  In soils, chemical heterogeneity, biological diversity, and strain variation not captured by genomic consensus sequences complicate soil proteomic experiments and data analyses.  This presentation will discuss a series of protein extraction methods for different types of soils that effectively allow characterization of the functional potential of resident microbes in soil.  Stable isotope probing is a method that identifies and targets active components in a complex system. We amended soils collected from a Hopland CA site with ¹³C labeled glucose and, using advanced protein SIP technology, determined the overall proteomic profile of the microbes. Additionally, we tracked the label into those proteins that were synthesized in response to glucose.  Along with the establishment of these methods in soils, we identified an increase in proteins related to glucose metabolism, sugar transport and sulfur metabolism.   The further application of these methods is poised to provide fundamental knowledge on the structure and function of the community within these soils.