FIG. 4.

LC/MS chromatograms of cultures of B. elkanii USDA94 (wild-type), USDA94Δrtx::Ω1, and USDA94Δrtx::Ω1(pRTF1-F1). (A) PITC derivatives of serinol were detected at m/z 227 and eluted at a retention time of 3.8 min. (B) PITC-dihydrorhizobitoxine was detected at m/z 463 and eluted at a retention time of 10.4 min. (C) PITC-rhizobitoxine was detected at m/z 461 and eluted at a retention time of 10.4 min. The large-deletion mutant USDA94Δrtx::Ω1 ceased to produce serinol, dihydrorhizobitoxine, and rhizobitoxine. However, these compounds were again produced after introduction of pRTF1-F1 into the mutant.