Fig. 1

Putative type II TA systems on megaplasmid of S. oneidensis MR-1 and characteristics of ParDE TA system. (a) Distribution of six putative type II TA systems on megaplasmid of S. oneidensis MR-1. The ParDE TA system is marked in red rectangle. (b) Genomic organization of putative ParDE (SO_A0087-A00887) TA system. The start and stop codons are highlighted in bold."

Fig. 2

Identification of SO_A0087-0088 as a TA system in S.oneidensis MR-1. (a) The CFU of exponentially growing MR-1 was measured over time after the expression of pBBR2-based constructs that were induced with 0.3% L-arabinose at OD600 0.1. Data points represent average and standard deviation of three independent experiments. (b) CFU of pBBR2-based constructs after 6-h induction with 10 mM L-arabinose. (c) Growth of MR-1 harboring pBBR2-based constructs on LB plates containing 50μg/ml kanamycin with or without 0.3% L-arabinose. Plates were incubated for 16 h. (d) Morphology of pBBR2-based constructs under contrast microscope. Cells for observing were grown in LB and induced with 0.3% L-arabinose for 2 h"

Fig. 3

Identification of SO_A0087_0088 as a TA system in E.coli BW25113. (a) The CFU of exponentially growing E.coli BW25113 was measured over time after the expression of pBAD-based constructs that were induced with 10 mM L-arabinose at OD600 0.1. Data points represent average and standard deviation of three independent experiments. (b) CFU of pBAD-based constructs after 4-h induction with 0.3% L-arabinose. (c) Growth of E.coli BW25113 harboring pBAD-based constructs on LB plates containing 100μg/ml carbenicillin with or without 0.3% L-arabinose. Plates were incubated for 16 h. (d) Morphology of pBAD-based constructs under contrast microscope. Cells for observing were grown in LB and induced with 0.3% L-arabinose for 6 h"

Fig. 4

Antitoxin SO_A0087 binds to promoter of SO_A0087- SO_A0088 in vitro. (a) Promoter region that is 223 bp upstream the start codon of SO_A0087. The predicted inverted repeat is marked with arrows. (b) Purification of antitoxin SO_A0087. (c) EMSA to detect interaction between P223 promoter DNA and antitoxin SO_A0087"

Fig. 5

ParE proteins alignments and mutation of active sites of SO_A0088. (a) Proteins of ParE family were aligned using MATFF server and displayed on EsPript 3.0. (b) Toxicity detection of SO_A0088 mutants in E.coli K-12 host obtained from epPCR assay on LB plates with or without 0.3% L-arabinose. (c) Predicted 3-D structure of SO_A0088. Residues obtained by epPCR assay that affected SO_A0088 toxicity are shown in white"