Abstract:To identify the antimicrobial components produced by the symbiotic or epiphyte bacterium DNC2 from Strongylocentrotus intermedius and investigate their anti-tumor potential，both bacterial cells and fermentation broth of DNC2 were filtered through a 0.22 μm filter membrane，while the proteins from the ammonium sulfate-precipitated fermentation broth were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis （SDS-PAGE）. Subsequently，the antimicrobial activities of the bacterial cells，cell-free fermentation broth，and protein fractions were assessed using the filtering paper assay. Additionally，the antifungal activity of the antimicrobial components was determined using the agar block method，while the anti-tumor activity was evaluated using the prawn toxicity test and methyl thiazolyl tetrazolium （MTT） assay. The results indicated that the fermentation broth of DNC2 exhibited stronger antimicrobial activity than the bacterial cells，while the protein fraction from the fermentation broth showed potent antimicrobial effects. The extracellular crude proteins of DNC2 showed inhibitory activity against Gerlachia nivalis，Fusarium moniliforme，Fusarium axysporumf. sp. Niveum，Ralstonia solanacearum，Botrytis cinerea，and Fusarium oxysporum Schlecht，with particularly notable inhibition against the latter four pathogens. Moreover，the crude proteins also suppressed the proliferation of chronic myeloid leukemia cells K562，hepatocellular carcinoma cells HepG2，and breast cancer cells MCF-7 and MDA-MB-231. At a concentration of 300 μg/mL，the inhibition rates reached 95.87%，90.40%，77.71%，and 95.67%，respectively. In summary，the extracellular proteins of the symbiotic or epiphyte bacterium DNC2 from S. intermedius have broad-spectrum antimicrobial and anti-tumor activities.