In order to reveal the inhibitory effect of the extract of fermentation broth from Streptomyces lavendulae X33 (hereafter referred to as SLFE) on Penicillium digitatum (P.digitatum),a postharvest pathogen of citrus,the cellular integrity and related cell contents of P.digitatum treated with SLFE were determined.Scanning electron microscope,Raman spectrum,fluorescence probe,fluorescence spectrum and fluorescence quantitative PCR were used to observe the effects of SLFE treatment on mycelium morphology,cell response and DNA.The results showed that the hyphae of the strain Pd165 appeared withered,twisted and folded,and the conidiophores and conidia were abnormal by the treatment of 1.2 mg/mL SLFE,and moreover,the sporulation inhibition rate was as high as 94.86%.At the same time,the cell integrity of the strain was seriously damaged by SLFE,which acted as triggers for an increase in the characteristic peaks of fatty acids,nucleic acids and proteins in the extracellular supernatant (1 129,1 330,1 565 cm-1),and the massive exudation of intracellular sugars,nucleic acids and soluble proteins,and a decrease of the pyruvate content.In addition,SLFE treatment destroyed the conformation and structure of P.digitatum genomic DNA and upregulated the expression levels of genes related to cell integrity,sporulation,metabolism and oxidative stress (cej60377.1,oko99898.1,crl18986.1,kzn90160.1).The results suggested that SLFE treatment damaged the integrity of P.digitatum cells,disturbed the original homeostasis of cells,and seriously destroyed the conformation of DNA and the morphology of mycelium.