This study describes the reproductive pattern of Micromonospora vulgaris, a thermophilic actinomycete isolated from composts and canned ham. Unlike mesophilic Micromonospora species, M. vulgaris consistently produces a secondary aerial mycelium under optimal laboratory conditions and in grass composts at elevated temperatures. The organism reproduces through small, refractile spores borne singly on lateral branches of vegetative mycelium. The aerial mycelium consists of abundantly branched, hydrophobic filaments that rapidly segment and also produce single lateral spores. The vegetative mycelium exhibits thermophilic characteristics including rapid cell elongation and disintegration within 1-2 days. Spore germination occurs via one to four germ tubes that develop into branching filaments. The aerial spores demonstrate heat resistance and are produced in greater quantities than vegetative spores. This complex reproductive strategy appears well-suited to the organism's ecological niche in high-temperature compost environments, where it competes with thermophilic bacteria. The author observed seven strains continuously over 2-3 years using slide cultures, liquid media, and agar plates incubated at 55-60°C.

Key findings

• Micromonospora vulgaris uniquely produces a consistent secondary aerial mycelium, distinguishing it from mesophilic Micromonospora species which lack this structure
• The organism exhibits one of the most complex reproductive patterns among actinomycetes, with both vegetative and aerial mycelium producing single lateral spores
• Aerial spores are heat-resistant and produced in greater quantities than vegetative spores, providing an adaptive advantage in high-temperature compost environments
• The aerial mycelium has hydrophobic properties and higher oxygen uptake than vegetative mycelium, enabling prolonged survival at elevated temperatures
• Thermophilic characteristics include rapid cell elongation, wide spacing between branches, and mycelial disintegration within 1-2 days rather than months as in mesophilic species