Abstract
virulent and most dreadful viral outbreaks in shrimp culture. The potential antibacterial effects of Bacillus subtilis silver nanoparticles (AgNPs) from the gut of Litopenaeus vannamei were studied. The AgNPs has ~ 420 nm in UV-visible spectrum, diameter 5-25 nm with smooth spherical shape (characterized by transmission electron microscopy) and 2θ values corresponding to the presence of silver crystal (X-ray diffraction spectrum). The AgNPs showed promising activity against Vibrio parahaemolyticus (21.25 ± 2.55 mm) and V. harveyi (19.27 ± 1.36 mm) as compared with B. subtilis, silver nitrate (AgNO3) and control. Four different experiments were conducted using different feeding behavior of L. vannamei. In comparison to untreated control group, final weight (14.89 ± 0.03 g), weight gain (9.36 ± 0.01), specific growth rate (SGR) 14.41 ± 0.09%, feed conversion ratios (FCR) 1.47 ± 0.12, higher survival and haemocyte counts were significantly greater in shrimp fed with AgNPs. The gill of entire experimental animal showed morphological alteration in histopathological investigation. The AgNPs were then tested for shrimp challenged with the V. parahaemolyticus. Statistical analysis revealed significant differences in shrimp survival between AgNPs, B. subtilis and control group. In the infective experimental study, cumulative survival of the control group (10 ± 0.321%) whereas the shrimp with AgNPs (90.66 ± 0.523%) and (71 ± 0.577%) with B. subtilis. Subsequently, real-time PCR was observed for immune related genes to determine the mRNA levels of prophenoloxidase (proPO), anti lipopolysaccharide factor (ALF2 and 4), peroxinectin (PE), superoxide dismutase (SOD), 18S, lipopolysaccharide and β -1,3-glucan-binding protein (LGBP ) and serine protein (SP). The expression of all immune related genes (mRNA levels) studied was significantly upregulated in the AgNPs diet shrimp in contrast to the B. subtilis and control. This study discovers that the biomastered AgNPs give a promising potential new tool for inhibiting vibriosis in shrimp culture.
Highlights
The aquaculture industry continues to expand as a crucial segment of the global seafood market [1]
7 presumptive silver producing strains were isolated from the gut of L. vannamei
AgNPs synthesized bacteria-16S rRNA gene sequence was deposited in the National Center for Biotechnology Information (NCBI) Gene Bank under the name of B. subtilis 1725505EJ1 (Accession number: J812207)
Summary
The aquaculture industry continues to expand as a crucial segment of the global seafood market [1]. The pacific white shrimp, L. vannamei is one of the most prominent marine aquaculture species [2,3]. It was first introduced in China in the late 1980’s. The term vibriosis refers to the bacteria of the genus Vibrio which causes disease associated to shrimp. They are the natural inhabitants of estuarine and marine environments, well known for causing vibriosis in fish worldwide and the prevention has become a major challenge in aqua farming [10,11]
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