PMC

TLC assay to test the ability of the eryA transcriptional mutants eryAI::t_rrn and eryAIII::t_rrn to bioconvert erythromycin C to erythromycin A. Erythromycin C (25 μg/ml) was added separately to 50-ml SCM cultures containing the eryA mutants and the eryBIV mutant, eryBIV::t_rrn. One milliliter of the culture broth from 0- to 4-day fermentations was extracted with ethyl acetate and analyzed by TLC. The eryBIV mutant was used as the positive control. Both S. erythraea NRRL2338 (data not shown) and eryBIV::t_rrn completely bioconverted all the supplemented erythromycin C to erythromycin A in less than 1 day between days 1 and 2 of the fermentation. 0−, no added erythromycin C; 0+, sample taken at the time of supplementation; 1 to 4, day of sampling following addition of erythromycin C; Std., TLC standards (M, 3-mycorosyl erythronolide B; E, erythronolide B; B, erythromycin B; A, erythromycin A; C, erythromycin C).

(A) Growth curve of mc²155, mc²155:Δ6212 and the complemented strain pMV361-6212/mc²155:Δ6212 in 7H9 medium. (B) Growth curve of mc²155, mc²155:Δ6212 and the complemented strain pMV361-6212/mc²155:Δ6212 in 7H9 medium with 1.56 mg/L erythromycin (*p < 0.05, **p < 0.01). (C) Killing curve for mc²155, mc²155:Δ6212 and the complemented strain pMV361-6212/mc²155:Δ6212 in 7H9 medium with 31.25 mg/L erythromycin (*p < 0.05, **p < 0.01, ***p < 0.001). (D) Killing curve for pMV261/mc²155 and pMV261-6212/mc²155 in 7H9 medium with 15.6 mg/L erythromycin (*p < 0.05, **p < 0.01, ***p < 0.001).

Plasma hormone and blood glucose changes after erythromycin infusion compared to saline. (A) Plasma octanoylated ghrelin levels decreased after erythromycin infusion, and increased after placebo infusion. The difference between erythromycin and placebo was significant at t = 30, 40, and 50 min (**p < 0.01). (B) Plasma motilin levels decreased after erythromycin infusion, and increased after placebo infusion, but this difference was not significant. (C) Blood glucose levels increased after erythromycin compared to placebo. The difference between erythromycin and placebo was significant at t = 30 (*p < 0.05). (D) Plasma insulin level increased after erythromycin infusion compared to placebo infusion. The difference between erythromycin and placebo was significant at t = 20 and 30 min (**p < 0.01). Data are shown as mean ± SEM.

The macrolactone ring is in red color and the 5-position disosamine sugar is in blue color. The different functional groups between SIPI-8294 and erythromycin are in pink color for SIPI-8294 and in black color for erythromycin.