The phosphorus source phytate changes the composition of the cell wall proteome in Bacillus subtilis

Phytate is the most abundant phosphorus source in plants. Since Bacillus subtilis is a soil-dwelling bacterium, the focus of this study was to investigate whether it can use phytate as a phosphorus source. The extracellular proteome analysis revealed that phytate is an alternative phosphorus source to overcome the phosphate starvation response in B. subtilis. However, the phytase was not induced neither under phosphate starvation conditions nor by phytate addition. Surprisingly, the proteome analyses demonstrated a re-distribution of the major cell wall protease WprA from the cell wall to the extracellular medium in phytate-supplemented medium. In contrast, several cell wall proteins such as autolysins and autolysin modifier proteins (e.g., LytB, -C, -D, -E, -F) are increased in the cell wall proteome in response to phytate which is not accompanied by increased transcription of the corresponding genes. These effects of phytate on the composition of the B. subtilis cell wall proteome do not depend on the acidic conditions, the increased sodium ion concentration, and the increased cell lysis. In addition, the previously predicted as cytoplasmic protein oxalate decarboxylase OxdC was identified as the most abundant cell wall protein which was induced at the transcriptional level due to the acidic conditions caused by phytate.