Secondary metabolites of Antarctic fungi antagonistic to aquatic pathogenic bacteria

Abstract

AbstractPolar microbial derived antibiotics have potential as alternatives to traditional antibiotics in treating fish against pathogenic bacteria. In this paper, 23 strains of polar fungi were fermented to detect bacteriostatic products on three aquatic pathogenic bacteria, subsequently the active fungus was identified. It was indicated that secondary metabolites of 23 strains weredistinct; of these, the extract of strain B-7 (belonging toBjerkanderaaccording to molecular identification) demonstrated a strong antibacterial activity toStreptococcus agalactiae,Vibrio anguillarumandAeromonas hydrophilaATCC7966 by Kirby-Bauerpaper strip method. During one fermentation cycle, the pH curve of the fermentation liquor became lowest (4.0) on the 4thday and rose back to 7.6 finally after 5 days, The residual sugar curve was decreased before stablising on the 6thday. It is presumed that a large amount of alkaline secondary metabolites might have been produced during fermentation. This study focuses on antagonism between aquatic pathogenic bacteria and fermentation metabolites from Antarctic fungi for the first time, which may provide data on research of antibiotics against aquatic pathogenic bacteria.