10 mM MTZ has toxic effects on larval tissues independent of microbiota. (A-L) Confocal images of CVZ (A-F) and GF (G-L) 8xNFκB:eGFP 5 dpf larvae that were either kept as a negative control (no MTZ, A,D,G,J) or treated with 10 mM MTZ from 3 to 5 dpf (10 mM MTZ, B,C,E,F,H,I,K,L). MTZ-treated larvae either inflated or failed to inflate their swim bladders. Both CVZ and GF larvae showed the same response – an increase in the number of cells undergoing NFκB signaling in the gut, neuromasts (arrowheads) and skin (arrows) when treated with 10 mM MTZ. (A-C,G-I) 20× z-stacked fluorescent images. (D-F,J-L) Same z-stack imposed over brightfield image. Scale bars: 100 µM. CVZ, conventionalized; GF, germ free; MTZ, metronidazole; SB, swim bladder.
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