(A) The arrangement of the FR900098 biosynthetic genes. The end points of largest deletions that do not eliminate antibiotic production (Δ126 and Δ191) and smallest deletions that do (Δ061 and Δ136) are also shown. Δ126 ends 117 bp before the end of frbA, Δ191 removes 2233 of 2660 bp of frbA, Δ136 removes 934 of 1886 bp of frbH, and Δ191 removes 51 of 1886 bp of frbH. The region from frbA to frbH is sufficient for production of FR900098 in the heterologous host S. lividans. (B) The proposed biosynthetic pathway for FR900098. The assignment of ORFs to chemical steps is based on the proposed functions as deduced from sequence comparisons. Intermediates in the production of FR900098: I. phosphoenolpyruvate, II. 3-phosphonopyruvate, III. 2-phosphonomethylmalate, IV. 3-phosphonomethylmalate, V. 2-oxo-4-phosphonobutryate, VI. 2-amino-4-phosphonobutyrate, VII. 3-aminopropylphosphonate, VIII. N-hydroxy-3-aminopropylphosphonate, IX. N-acetyl-3-aminopropylphosphonate.