Abstract
BackgroundVibrio pathogens are causative agents of mid-culture outbreaks, and early mortality syndrome and secondary aetiology of most dreadful viral outbreaks in shrimp aquaculture. Among the pathogenic vibrios group, Vibrio alginolyticus and V. harveyi are considered as the most significant ones in the grow-out ponds of giant black tiger shrimp Penaeus monodon in India. Use of antibiotics was banned in many countries due to the emergence of antibiotic-resistant strains and accumulation of residual antibiotics in harvested shrimp. There is an urgent need to consider the use of alternative antibiotics for the control of vibriosis in shrimp aquaculture. Biofilm formation is a pathogenic and/or establishment mechanism of Vibrio spp. This study aims to develop novel safe antibiofilm and/or antiadhesive process using PHB to contain vibrios outbreaks in shrimp aquaculture.ResultsIn this study a poly-hydroxy butyrate (PHB) polymer producing bacterium Brevibacterium casei MSI04 was isolated from a marine sponge Dendrilla nigra and production of PHB was optimized under submerged-fermentation (SmF) conditions. The effect of carbon, nitrogen and mineral sources on PHB production and enhanced production of PHB by response surface methods were demonstrated. The maximum PHB accumulation obtained was 6.74 g/L in the optimized media containing 25 g/L starch as carbon source, 96 h of incubation, 35°C and 3% NaCl. The highest antiadhesive activity upto 96% was recorded against V. vulnificus, and V. fischeri, followed by 92% against V. parahaemolyticus and V. alginolyticus and 88% inhibition was recorded against V. harveyi.ConclusionIn this study, a thermostable biopolymer was chemically characterized as PHB based on 1HNMR spectra, FT-IR and GC-MS spectra. The NMR spectra revealed that the polymer was an isocratic homopolymer and it also confirmed that the compound was PHB. The antiadhesive activity of PHB was determined in microtitre plate assay and an effective concentration (EC) of PHB (200 μl containing 0.6 mg PHB) was confirmed by confocal laser scanning microscopic analysis of vibrio biofilm on pre-treated glass and polystyrene surfaces. This is a first report on anti-adhesive activity of PHB against prominent vibrio pathogens in shrimp aquaculture.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-014-0114-3) contains supplementary material, which is available to authorized users.
Highlights
Gram negative Vibrionacea represent the most dreadful pathogenic bacteria causing disease in both grow-out ponds and hatcheries
The purified poly-hydroxy butyrate (PHB) was characterized by FTIR, Gas chromatography (GC)-MS and NMR spectra and thermal stability of the polymer was analysed by thermal gravimetric and differential scanning calorimetric analysis. This is a first report on anti-adhesive activity of PHB against prominent vibrio pathogens in shrimp aquaculture
Isolation, screening and identification of PHB producer MSI04 In this study, 43 unique bacterial colonies were isolated from a marine sponge Dendrilla nigra but the stable isolates after subcultures were used in the screening
Summary
Gram negative Vibrionacea represent the most dreadful pathogenic bacteria causing disease in both grow-out ponds and hatcheries. Vibrio alginolyticus and V. harveyi are considered as the most significant ones in the grow-out ponds of giant black tiger shrimp Penaeus monodon in India [1]. Because of the development of resistance to the commonly used antibiotics, there is an urgent need to consider the use of alternative antibiotics for the control of vibriosis [1,2]. Use of antibiotics to control vibrios in shrimp aquaculture is not allowed in most of the countries and so it is necessary to develop an alternative pathogen control method for shrimp production [3]. Among the pathogenic vibrios group, Vibrio alginolyticus and V. harveyi are considered as the most significant ones in the grow-out ponds of giant black tiger shrimp Penaeus monodon in India. There is an urgent need to consider the use of alternative antibiotics for the control of vibriosis in shrimp aquaculture. This study aims to develop novel safe antibiofilm and/ or antiadhesive process using PHB to contain vibrios outbreaks in shrimp aquaculture
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