Abstract: This experiment was conducted to isolate and identify a microbial strain producing rosy pigment， and to study its antibacterial activity. The microbial strains were identified by morphological characteristics， physiochemical properties and 16S rRNA gene sequence analysis. The optimization of temperature and illumination condition for rosy pigment production was investigated by variable-controlling approach. Ultrasonic fragmentation was used to extract pigment and analyze its yield and absorption spectrum. In eventually， antagonism assay to pathogens also be carried out by filter-paper method. The results showed that: （1） a screened strain Dse-01 was identified as Serratia marcescens; （2） The strain showed significant impact on chromogenesis under the condition of 25-35 ℃， especially at 30 ℃， which was not affected by illumination; （3） The strain was cultured at 30 ℃ for 24 h with a shaking speed of 150 r·min-1 and the extracts was prodigiosin， whose production could reach (567.90±7.77) mg·L-1; （4） the pathogenic Escherichia coli and Salmonella spp. were resistant to four active substance: Serratia marcescens， sediment of Serratia marcescens， supernatant of Serratia marcescens and pigment extraction from Serratia marcescens， whereas， Staphylococcus aureus was sensitive to all of these active products except the supernatant.

Key words: Serratia marcescens, prodigiosin, biological antagonism