Screening and antibacterial activity of bacteriocin-producing bacteria in intestine of Dendrolimus punctatus

Abstract:

[Background] Bacteriocin is a group of antibacterial-peptide substance produced by bacteria, with an inhibition and killing effect on various pathogenic bacteria. Insect, as the most abundant animal groups, is one of animals containing the most abundant and diverse intestinal microbial community in the world. Insect intestines may contain a rich bacteriocin-producing bacteria resource. [Objective] Sampling Dendrolimus punctatus larvae as experimental materials, its intestinal bacteria were isolated, and these bacteria were further cultured and identified. Bacteriostatic bacteria with obvious inhibitory effect on typical pathogens were obtained. Bacteriostatic substance was preliminarily speculated, and bacteriocin-producing bacteria with high bacteriostatic activity were investigated to further enrich resources of the bacteriocin-producing bacteria. [Methods] The bacteria were isolated by traditional-pure culture method, activity of the bacteriostatic substance was detected by using Oxford cup method, and bacteriocin-producing species were determined by combining morphological characteristics and 16S rRNA gene sequences of colony; interference of organic acid and hydrogen peroxide was further eliminated, and the bacteriostatic substance was preliminarily demonstrated with protein-like properties. [Results] Thirteen strains of the bacteriocin-producing bacteria were screened from intestine of the D. punctatus larvae, which belong to genera Bacillus, Staphylococcus, Psychrobacter and Enterobacter. Results of bacteriostatic experiments showed that these 13 strains have a certain degree of inhibitory effects on two species of typically pathogenic indicator bacteria, Staphylococcus aureus and Escherichia coli. In particular, bacteriocin produced by Bacillus amyloliquefaciens MW-1 maintained a good antibacterial activity after treating with different temperature and pH conditions, and an optimum bacteriostatic activity was obtained under pH 7.0 and 37 °C. [Conclusion] Many species of the bacteriocins-producing bacteria in the intestine of the D. punctatus larvae present antibacterial effects on important pathogens. The strain MW-1 with high bacteriostatic activity for pathogen shows potential to replace antibiotic, bacteriocin of which exhibited a good stability under heat, acids and alkaline treatments.