Development of an algae extract-based culture medium for Paenibacillus larvae without animal-derived components.

The cultivation of Paenibacillus larvae, the etiological agent of American foulbrood, traditionally relies on media containing animal-derived nutrients. In response to ethical and practical concerns associated with such components, we developed and validated a new culture medium based on an algae extract. The formulation includes Chlorella as the principal nutrient source and is supplemented with uric acid and L-tyrosine to support spore germination under conditions resembling the honeybee larval gut. The method includes optimized procedures for dissolving sparingly soluble components and minimizing nutrient degradation. Performance of the new medium was comparable to that of MYPGP and other conventional media in supporting spore germination and vegetative growth of P. larvae. • Eliminates the need for animal-derived components through the use of microalgal nutrients • Supports robust germination and colony development of P. Larvae • Provides an ethical and cost-efficient medium suitable for diagnostic and research applications.