This study investigated a germination inhibitor (GI) produced by Streptomyces viridochromogenes spores. Germinating spores excrete GI into the surrounding medium, which blocks germination of dormant spores. The GI was purified 51-fold from growth culture filtrates through chloroform extraction and column chromatography, yielding a low molecular weight substance (less than 1000 Da) that is soluble in alcohol and water. The GI inhibits growth and respiration of some Gram-positive bacteria and functions as an inhibitor of calcium-dependent ATPase in spore and mycelial membranes of the producing organism. Four inhibitory activities—germination inhibition, respiration inhibition, growth inhibition, and ATPase inhibition—co-purified and showed constant activity ratios throughout purification, indicating they derive from the same compound. The GI is produced during stationary growth phase and is released from germinating spores concurrently with carbon excretion. The authors suggest GI plays a regulatory role in spore dormancy and germination through ATPase inhibition, while also functioning as an antibiotic against certain bacteria.

Key findings

• S. viridochromogenes produces a low molecular weight (< 1000 Da) germination inhibitor that blocks spore germination through ATPase inhibition
• The germination inhibitor co-purifies with antibiotic, respiration-inhibiting, and growth-inhibiting activities, suggesting a single active compound
• GI is produced during stationary growth phase and released from germinating spores with kinetics parallel to carbon excretion
• The inhibitor selectively inhibits calcium-dependent ATPase in membranes of the producing organism and some Gram-positive bacteria
• GI reversibly blocks germination initiation in unactivated spores but only partially inhibits germination of heat-activated spores