Optimization of protein extraction methods for root-associated microbes in Arabidopsis

The goal of this study was to optimize protein extraction methods to study root-associated bacteria in Arabidopsis. For this we inoculated Arabidopsis seedlings grown in agar plates with a synthetic community (SynSom) composed of four different strains (Variovorax paradoxus, Arthrobacter sp, Agrobacterium sp. and Pseudomonas sp.. Twelve days after inoculation we extracted proteins from the roots using six different protein extraction methods each in triplicates. These methods were a combination of different extraction buffers (SDS or Triton-based) and mechanical disruption methods (bead-beating, N2 grinding, glass homogenizer and freeze-thaw cycles) We found that bead-beating the roots with lysing matrix E in SDT lysis buffer yielded the highest numbers of microbial protein identification and enhanced the detection of proteins derived from gram positive bacteria.