Multi-algicidal mechanism and potential application of Streptomyces sp. strain P-10 against the bloom-forming Prorocentrum donghaiense.

This article focuses on the algicidal efficacy and application potential of Streptomyces sp. P-10, a marine sponge-derived actinobacterium, against the harmful algal bloom (HAB) species Prorocentrum donghaiense. Streptomyces sp. P-10 employs a dual algicidal strategy combining direct physical interaction via mycelial entanglement and indirect inhibition through secretion of bioactive compounds, notably cellulase (201.37 μg·(mL·min)⁻¹) that degrades cellulose-based algal cell walls, and N-acetyltryptamine (IC₅₀ = 37.88 μg·L⁻¹) that disrupts photosynthetic electron transport. Laboratory and natural bloom water experiments demonstrated that P-10 effectively lyses P. donghaiense cells (up to 95% lysis in 96 hours) and also inhibits co-occurring harmful species such as Karenia mikimotoi, with ultrastructural analyses confirming cellular damage and photosynthetic impairment. The strain’s formation of 1–3 mm mycelial pellets enhances environmental resilience by resisting dilution and predation, suggesting its promise as an eco-friendly, sustainable biocontrol agent for managing HABs in marine ecosystems.