Fig. S1. Effect of the retrieved ClpXP proteins in metal (A) and high temperature (B) resistance.

A. Drop assay of grown overnight cultures of E. coli DH10B carrying clpP and clpXP genes. Serial dilutions (0–10−4) of each culture were dropped on LB plates containing 2.25 mM Ni+2, 0.8 mM Cd+2, 6 mM As+5 and 1.25 mM Co+2.

B. Heat shock assay of E. coli DH10B carrying clpP, clpX and clpXP. Cultures were grown in LB-Ap until they reached the mid exponential phase. Then, resuspended cell pellets of one millilitre of each culture were incubated at 50°C for 0 and 60 min. Percentage of survival was then calculated as the number of cfu ml−1 remaining after the temperature treatment divided by the initial cfu ml−1 at time zero. In both metal and heat shock experiments E. coli DH10B carrying empty pSKII+ was used as a negative control. Each assay was performed at least three times using independent cultures.

Table S1. Strains of P. putida KT2440 and B. subtilis PY79 used in this study.

Table S2. Primers used for subcloning of the different ORFs in plasmids (A) pSKII+ in E. coli (B) pARP5 in P. putida and (C) pdr111 in B. subtilis.

Table S3. Acid resistance of clones harbouring plasmids pME1 to pME11.

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