Figure 4. Construction of B. cereus siderophore mutants.

Genetic organization of petrobactin (A) and bacillibactin (B) biosynthetic gene clusters in B. cereus strain ATCC 14579 is represented. The deleted genes (in black) and the orientation of the antibiotic cassettes (tetracycline, tet^R and kanamycin, km^R) are depicted. Deletions were created by integrative recombination in the loci using upstream and downstream region (∼1 kb each) amplified with primer pairs (+) and (x) for the asb locus or (*) and (°) for entA gene. In addition, the promoter region (359 bp) of entA was cloned between the km^R cassette and dhbC (P in gray box) to ensure transcription of downstream genes. For ΔentA complementation, (□) represent the primers used to amplify the fragment cloned in pHT304 plasmid.