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

This study sought to assess the algicidal efficacy of Streptomyces sp. P-10 against Prorocentrum donghaiense and evaluate its real-world application potential.

Streptomyces sp. P-10's supernatant and mycelial pellets demonstrated potent algicidal effects against P. donghaiense, with 95% and 80% lysis rates within 96 h, respectively. The supernatant contained N-acetyltryptamine, which at an IC50 of 37.88 μg·L-1, significantly inhibited algal photosynthesis. It also exhibited cellulase activity as 201.37 μg· (mL·min)-1, degrading algal cell walls. Both N-acetyltryptamine and cellulase, alone or in concert, hindered photosynthesis. SEM and TEM analyses revealed that P-10 mycelia enwrapped and lysed algal cells, while supernatant components compromised cell wall integrity and induced cytoplasmic vacuolation. Notably, P-10 sustained growth in algal cultures and bloom waters without additional nutrients.

Streptomyces sp. P-10 effectively kills P. donghaiense via direct mycelial encasement and indirect bioactive compounds and cellulase activity, inhibiting algal growth and photosynthesis.