add art soil preparation study and protocol

studies/ArtSoilPreparation/protocols/ArtSoilPreparationProtocol.md

+## ArtSoil preparation
+
+For the preparation of 10% autoclaved soil suspension, sieved CAS (to remove pebbles) was dissolved in deionized water and autoclaved three times before use. Live bacterial suspension was prepared by inoculating fresh CAS into 10% autoclaved soil suspension to achieve desired bacterial dilution (Korenblum, E. et al., 2020). Autoclaved half-strength Murashige-Skoog (½ MS) media including MES (Duchefa Biochemie) and supplemented with 1% agar was cooled to 40–45°C before it was inoculated with live bacterial suspension. Approximately 50 mL of ArtSoil media was used for each 12 cm x 12 cm culture plate (Figure S2B). Sterilized *A. thaliana Col-0* seeds were sown and germinated on ArtSoil, and incubated in a plant growth chamber for 4 weeks under standard growth conditions.
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