关键词: 豨莶草, 侧孢短芽孢杆菌, 氨苄西林, 耐碱, 超滤

Abstract: Herba siegesbeckiae has many healing values,and our aim is to isolate and screen highly active antagonistic endophytes from its fruits. The biological characteristics of anti-infective bacterium C-5-1 were determined by antagonistic experiment,morphological observation,physiological and biochemical tests,sequence alignment of 16S rRNA gene,analysis of phylogenetic tree,measuring OD₆₀₀,drug sensitive tests,and ultra-filtration centrifugation. The results showed that the C-5-1 was identified as Brevibacillus laterosporus and was sensitive to various pathogenic bacteria,especially Pseudomonas aeruginosa. The strain C-5-1 had limited tolerance to low pH and highly saline environments,i.e.,inhibited completely or even died in pH≤5 or more than 15% NaCl,but it grew well in pH≥7 and 0-5% NaCl,suggesting that C-5-1 had good alkali resistance,but not resistant to acid and salt. Screening experiment revealed that the antibiotic ampicillin was highly sensitive to C-5-1,but resistant to 5 pathogenic bacteria. Fermentation supernatant of C-5-1 contained two antibacterial substances and relative molecular mass of both was less than 2 000. Conclusively,H. siegesbeckiae having excellent microbial resources will be a key resource for the development of anti-bacteria drugs.

Key words: Herba siegesbeckiae, Brevibacillus laterosporus, ampicillin, alkali-resistant, ultra-filtration centrifugation