Utilizing a mutant of Micromonospora inyoensis which requires the addition of 2-deoxystreptamine for sisomicin production, the bioconversion of 2-deoxystreptamine containing pseudodisaccharides and pseudotrisaccharides into sisomicin was demonstrated. The trisaccharides tested were structurally related minor components found in the sisomicin or gentamicin fermentations. Based upon the specificity of the structural configuration of those compounds which were converted to sisomicin versus those which were not, a pathway for the biosynthesis of sisomicin is proposed.