2"-N-formimidoylistamycin A and B produced by Streptomyces tenjimariensis

Central composite design for optimizing istamycin production by Streptomyces tenjimariensis

Istamycins (ISMs) are 2-deoxyfortamine-containing aminoglycoside antibiotics (AGAs) produced by Streptomyces tenjimariensis ATCC 31603 with broad-spectrum bactericidal activities against most of the clinically relevant pathogens. Therefore, this study aimed to statistically optimize the environmental conditions affecting ISMs production using the central composite design (CCD). Both the effect of culture media composition and incubation time and agitation rate were studied as one factor at the time (OFAT). The results showed that both the aminoglycoside production medium and the protoplast regeneration medium gave the highest specific productivity. Results also showed that 6 days incubation time and 200 rpm agitation were optimum for their production. A CCD quadratic model of 17 runs was employed to test three key variables: initial pH, incubation temperature, and concentration of calcium carbonate. A significant statistical model was obtained including, an initial pH of 6.38, incubation temperature of 30 ˚C, and 5.3% CaCO3 concentration. This model was verified experimentally in the lab and resulted in a 31-fold increase as compared to the unoptimized conditions and a threefold increase to that generated by using the optimized culture media. To our knowledge, this is the first report about studying environmental conditions affecting ISM production as OFAT and through CCD design of the response surface methodology (RSM) employed for statistical optimization. In conclusion, the CCD design is an effective tool for optimizing ISMs at the shake flask level. However, the optimized conditions generated using the CCD model in this study should be scaled up in a fermenter for industrial production of ISMs by S. tenjimariensis ATCC 31603 considering the studied environmental conditions that significantly influence the production proces.

Istamycin aminoglycosides profiling and their characterization in Streptomyces tenjimariensis ATCC 31603 culture using high-performance liquid chromatography with tandem mass spectrometry

A high-performance liquid chromatography with electrospray ionization ion trap tandem mass spectrometry method was developed and validated for the robust profiling and characterization of biosynthetic congeners in the 2-deoxy-aminocyclitol istamycin pathway, from the fermentation broth of Streptomyces tenjimariensis ATCC 31603. Gradient elution on an Acquity CSH C₁₈ column was performed with a gradient of 5 mM aqueous pentafluoropropionic acid and 50% acetonitrile. Sixteen natural istamycin congeners were profiled and quantified in descending order; istamycin A, istamycin B, istamycin A₀ , istamycin B₀ , istamycin B₁ , istamycin A₁ , istamycin C, istamycin A₂ , istamycin C₁ , istamycin C₀ , istamycin X₀ , istamycin A₃ , istamycin Y₀ , istamycin B₃ , and istamycin FU-10 plus istamycin AP. In addition, a total of five sets of 1- or 3-epimeric pairs were chromatographically separated using a macrocyclic glycopeptide-bonded chiral column. The lower limit of quantification of istamycin-A present in S. tenjimariensis fermentation was estimated to be 2.2 ng/mL. The simultaneous identification of a wide range of 2-deoxy-aminocyclitol-type istamycin profiles from bacterial fermentation was determined for the first time by employing high-performance liquid chromatography with tandem mass spectrometry analysis and the separation of istamycin epimers.

N-formimidoyl fortimicin A synthase, a unique oxidase involved in fortimicin A biosynthesis: purification, characterization and gene cloning

Micromonospora olivasterospora, a fortimicin A (FTM A, astromicin) producer, was found to carry an enzyme that converts FTM A to N-formimidoyl FTM A (FI-FTM A). This enzyme (FI-FTMase) was purified to homogeneity and shown to be a flavin adenine dinucleotide (FAD) enzyme. Tracer experiments proved that the formimidoyl group was derived from C-2 of glycine via oxidation of the amino acid in the presence of FTM A and oxygen. The gene encoding this enzyme, fms 14, was cloned using a 26-mer oligonucleotide probe, designed according to the N-terminal amino acid sequence of purified FI-FTMase, from a cosmid clone pGLM990, which has been shown to contain a cluster of FTM A biosynthetic genes. The nucleotide sequence, and biochemical and genetic analysis revealed that FI-FTMase is composed of four identical subunits of mol. wt. 52,000, and contains at least one FAD per subunit. DNA regions homologous to fms14 were found in two other producers of the fortimicin group of antibiotics, Dactylosporangium matsuzakiense ATCC31570 and Micromonospora sp. SF-2098.