In-depth study to decipher mechanisms underlying Arabidopsis thaliana tolerance to metal(loid) soil contamination in association with biochar and/or bacteria

•Arabidopsis growth and response were investigated on As and Pb contaminated soil.•Biochar and/or Bacillus effect on soil properties and plant growth was evaluated.•Bioinformatics-assisted proteomics deciphered associated molecular mechanisms.•Biochar-Bacillus combination assured the best Arabidopsis growth/defense tradeoff.