A new antibiotic, minosaminomycin, containing a myo-inosamine, was isolated from the culture broth of Streptomyces No. MA514-Al which is very closely related to Actinomyces aureomonopodiales. The antibiotic was produced by shaking culture of the strain at 30°C for 4 days in a medium containing 2.0% glucose, 2.0% starch, 2.0% soybean meal, 0.5% dry yeast, 0.25% NaCl, 0.32% CaCO₃, 0.0005% CuSO₄·5H₂O, 0.0005% MnCl₂·4H₂O and 0.005% ZnSO₄·7H₂O (adjusted to pH 7.4). Isolation and purification involved adsorption on Amberlite IRC 50 (Na⁺ form), elution with 1 N hydrochloric acid, neutralization with Amberlite IR 45 (OH⁻ form), adsorption on activated carbon, elution with 0.05 N hydrochloric acid in 50% methanol, concentration, readsorption on Amberlite CG 50 (70% NH₄⁺ form), elution with 0.3% ammonia, and further purification by cellulose powder (Whatman CF 11) column chromatography using butanol-pyridine-acetic acid-water (6:4:1:3) as solvent. The antibiotic is an amphoteric colorless powder melting at 225-260°C with decomposition, [α]²²ᴰ +30' (c 1.0, water), with molecular formula C₂₅H₄₆N₈O₁₀·2H₂O (anal. calcd.: C 45.85, H 7.70, N 17.12; found: C 45.40, H 7.83, N 17.10), pKa' values 2.9, 6.2, 8.1 and >12, no ultraviolet absorption except end absorption, and specific IR and PMR spectra. Acid hydrolysis yielded an aminocyclitol identified as (-)-1D-1-amino-1-deoxymyo-inositol (L-myo-inosamine-1) via comparison with hexaacetyl derivative (PMR identical to hexaacetyl-DL-myo-inosamine-1) and TACu method (positive contribution J[M]436(TACu)+767°), representing the first natural occurrence of this compound. Antimicrobial spectrum showed activity against mycobacteria (Mycobacterium smegmatis ATCC 607 MIC 1.56 mcg/ml, Mycobacterium phlei 6.25 mcg/ml, Mycobacterium tuberculosis H37Rv 16 mcg/ml) and weak activity against other bacteria (e.g., Micrococcus flavus FDA 16 50 mcg/ml, Shigella dysenteriae JS 11910 50 mcg/ml). Acute intravenous LD₅₀ in mice was 50-100 mg/kg.