High montmorillonite content may affect soil microbial proteomic analysis

• We examine the effects of montmorillonite and kaolinite on soil borne bacterium proteome with annotated proteome.
• The ratio of montmorillonite in soil has a negative effect on protein recovery and soil proteome analysis therefore the investigation about the interaction between protein and soil components are important to evaluate which information we can receive from soil proteins.
• More information on the protein interactions with highly reactive soil solid phases may be useful for improving the protein extraction protocols.

We studied the effects of high montmorillonite content in soil on the proteomic analysis of Cupriavidus metallidurans CH34 inoculated into model soils, containing a montmorilonite gradient. Bacterial proteomic analysis was conducted by two-dimensional gel electrophoresis (2-DE) coupled to mass spectrometry. The results showed that increasing the montmorillonite content in artificial soil the bacterial viability did not affect but the amount of extracted proteins and the number of protein spots in 2-DE decreased. Higher soil montmorillonite content also affected the protein identification, likely due to montomrillonite-induced conformational changes in proteins or degradation. Therefore the development of soil proteomics needs to increase the studies of interaction between protein and soil components as clays or humic substances. This experiment showed how the use of a model study can be an help to achieve more information about the complexity of soil and the fate of proteins in soil.