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. 2015 Feb 4;6:51. doi: 10.3389/fmicb.2015.00051

Figure 1.

Figure 1

The elevation of nlpI in E. coli inhibited the host cell growth. (A) The growth curves of the wild type (WT) strain MG1655 harboring the plasmid pQE80-nlpI or pQE80-nlpI-M in the presence or absence of inducer. Results shown are representative of three independent experiments. (B) The cellular morphology of Gram-stained bacteria. E. coli strain MG1655 harboring plasmid pQE80-nlpI was incubated in LB broth at 37°C with shaking until OD600 reached 0.5. Then the bacteria were induced by adding IPTG to a final concentration of 0.5 mM for 4 h. The cells were subsequently stained with Gram stain and observed by light microscope. Magnification, X1000. (C) Scanning electron microscopy examined the cellular morphology change and aggregation. Magnification, X10,000. (D) Bacteria were stained with DAPI and nucleoids were observed by fluorescence microscopy. Magnification, X1000. Scale bar, 10 μm. (E) Schematic presentation of NlpI and its three variants. The full length NlpI contains 294 amino acids including an N-terminal signal sequence and five TPR motifs. NlpI-M represents a mature NlpI protein without N-terminal signal sequence. NlpI-282 and NlpI-233 are truncated NlpI lacking the C-terminal 12 residues and the fifth TPR, respectively.