Micromonospora

Micromonospora ranks second only to Streptomyces in the number of antibiotics discovered, including gentamicin and other aminoglycosides that remain clinically essential. Unlike the filamentous growth of Streptomyces, Micromonospora forms substrate mycelium without aerial hyphae, demonstrating that the antibiotic-producing lifestyle doesn't require one specific morphology. Different actinomycete body plans can support the same ecological strategy.

Gentamicin, discovered from Micromonospora in 1963, exemplifies the continuing value of actinomycete screening even after the initial antibiotic golden age. The compound remains important for serious Gram-negative infections, particularly when other antibiotics fail. Micromonospora species have also yielded antitumor compounds, expanding their pharmaceutical relevance beyond antibiotics.

Micromonospora species frequently associate with marine invertebrates and plant roots, suggesting ecological roles beyond free-living soil existence. These associations may involve chemical defense—the invertebrate or plant hosts benefiting from their actinomycete associates' antibiotic production. Understanding these ecological relationships has directed bioprospecting toward underexplored niches: marine sponges, sea squirts, and plant endophytes harbor actinomycetes producing novel chemistry.