Isolation and screening of marine antagonistic bacteria and identification of a strain of antagonistic Bacillus sp.

72 strains of marine bacteria were isolated from marine samples collected at harbors and mangroves in Guangdong.These strains were screened for antimicrobial activities on Staphylococcus aureus,Bacillus subtilis,Escherichia coli,Candida albicans,Aspergillus niger and Penicillium funiculosum using cylinder-plate method.The results show that 12 strains have antimicrobial activity,accounting for 16.7% of the total,in which 7 strains are Bacillus spp.(accounting for 9.7%) and 5 strains are Gram-negative rod-shaped bacteria(accounting for 6.9%).The effects of antimicrobial activity produced by the antagonistic bacteria strains on the tested microorganisms are in the order of Gram-positive bacteriaGram-negative bacteriafilamentous fungi,and antimicrobial activity of marine spore-producing bacteria is stronger than that of the Gram-negative bacteria.The mean isolation rate of the marine antagonistic bacteria strains with antimicrobial activities from the mangrove samples is the highest,up to 25.3%.The strain NB7.2 with strong antimicrobial activity is identified as Bacillus subtilis according to its morphological,physiological and biochemical characteristics,and 16S rRNA sequence analysis.