(A) Selective ablation of macrophages. Transgenic fish with macrophage-specific expression of Gal4 [2] and Gal4-dependent expression of nitroreductase-mCherry fusion protein were incubated at 3 dpf with 5 mM metronidazole or vehicle for 24 hours. Neither transgenics nor controls exposed to metronidazole had any loss of viability or developmental defects. Ablation efficiency of macrophages is >90% (R. Gratacap and R. Wheeler,unpublished data). Scale bar = 100 µm. (B) OXYellow Candida albicans reports on oxidative stress in vivo. Zebrafish larvae were infected in the hindbrain with OXYellow C. albicans (expressing mCherry constitutively and EGFP under the oxidative stress-induced catalase promoter) and imaged at 24 hours post-infection. Green/red ratio quantifies oxidative stress (K. Brothers and R. Wheeler, unpublished dat). Scale bar = 10 µm. (C) Cryptococcus neoformans infects zebrafish embryos. Zebrafish were infected with EGFP-expressing C. neoformans and imaged. Clusters of fungi are seen in the tail (S. Johnston and R. Ma, unpublished data). Scale bar = 100 µm.