Fig. 5
Cytotoxicity, antiphagocytosis activity and ability to cause cell rounding of the MARTXVv1 domain-deletion mutants. a The effector domains in MARTXVv1. The triangle indicates the 469-bp deletion in the MD mutant, HL128, that results in a frameshift leading to a stop codon 26 bp downstream of the deletion. b, c, and d The bacteria were cultured in LB for 4 h, washed, and coincubated with RAW 264.7 cells at MOI 10 for 3 h (b) or 90 min (c, d). The cytotoxicity (b) and internalized bacterial number (c) were then estimated by LDH assay and gentamycin protection assay, respectively. The cell morphology (d) was examined under a light microscope. Bar = 50 μm. YJ016: WT strain; HL128: MD mutant. Data in b, and c were analyzed by one-way ANOVA followed by Tukey’s test. n = 3. Bars that show no significant difference from each other are labeled with the same letter, and those showing significant difference (P < 0.05) are labeled with different letters. Data in d are representative of three independent experiments