Putative nitroreductases of G. lamblia and E. histolytica. (A) Alignment of two hypothetical ferredoxin-nitroreductase fusion enzymes of G. lamblia (Gl1 and Gl2) with those of E. histolytica (Eh), Clostridium difficile (Cd) (incomplete microbial genome database), Clostridium acetobutylicum (Ca) (GenBank accession number 15026573), Chlorobium tepidum (Ct) (incomplete microbial genome database), D. vulgaris (Dv) (incomplete microbial genome database), and Geobacter sulfurreducens (Gs) (incomplete microbial genome database). Residues are shaded as described in the legend to Fig. 2A. A dash indicates the end of the available sequence for the E. histolytica ferredoxin-nitroreductase, which was truncated. Gaps are indicated by dots. (B) Alignment of putative oxygen-insensitive nitroreductases of G. lamblia (Gl) with those of Bacillus halodurans (Bh) (GenBank accession number 15612866), a Crenarchaeote sp. (Cs) (14548151), C. acetobutylicum (Ca) (15896791), and T. maritima (Tm) (15643149).