Janmejay Parhi

Paraprobiotic preparation from Bacillus amyloliquefaciens FPTB16 modulates immune response and immune relevant gene expression in Catla catla (Hamilton, 1822)

Abstract The present study evaluated the paraprobiotic effect of heat‐inactivated Bacillus amyloliquefaciens FPTB16 on immunological response and immune relevant gene expression in catla (Catla catla). Heat inactivation of viable cells of B. amyloliquefaciens was done at 60 °C for 2 h. For preparation of paraprobiotic supplemented diet, the heat‐inactivated bacteria were added to the basal diet (control) at three different inclusion levels i.e., 107, 108 and 109 cells g−1 diet. Fish (25.98 ± 2.57 g) were fed with these diets and various immune responses and immune relevant gene expressions were measured after 4 weeks of feeding. Biochemical parameters were also measured along with the immunological responses. Immunological parameters viz. oxygen radical production, serum lysozyme activity and total serum protein content showed significant enhancement (p < 0.05) in fish fed with 108 and 109 cells g−1 diet. Significant enhancement in myeloperoxidase activity was observed in all the dietary groups compared to control. Alkaline phosphatase activity showed significant enhancement (p < 0.05) in fish fed with 107 and 108 cells g−1 diet. Biochemical parameters viz. GPT, GOT and glucose content did not show any significant difference in any of the dietary groups. Immune relevant genes viz. IL‐1&bgr;, TNF‐&agr;, C3 and iNOS showed significantly higher expression in either liver or head‐kidney tissues in most of the cases. However, IFN‐&ggr; expression showed a down‐regulation pattern in both the tissues. In conclusion, the dietary supplementation of heat‐inactivated B. amyloliquefaciens enhanced the immunity of catla, particularly at 108 cells g−1 diet. The results collectively suggest the paraprobiotic applicability of B. amyloliquefaciens in aquaculture. HighlightsHeat‐inactivated Bacillus amyloliquefaciens FPTB16 was studied as paraprobiotic on catla immunity.The paraprobiotic preparation enhanced immune responses.Immune relevant gene expression was up‐regulated by paraprobiotic.Inclusion of 108 cells g−1 diet showed best immunostimulatory potential.

Advances in Bacteriophage Research for Bacterial Disease Control in Aquaculture

ABSTRACT Aquaculture sector suffers huge economic losses owing to frequent development of diseases caused essentially by bacterial and viral infections. Antibiotics were considered as effective therapeutic agents to control the bacterial diseases, however, due to problems associated with its frequent use, several antibiotics are banned and restricted in many countries. In such a scenario, the role of bacteriophage therapy, which is efficient, eco-friendly and a scientifically demonstrable solution to control antibiotic resistant bacterial infections, comes into play. Several bacteriophage have been isolated specific to various pathogenic bacteria, viz. Edwardsiella tarda, Edwardsiella ictaluri, Lactococcus garvieae, Pseudomonas plecoglossicida, Streptococcus iniae, Flavobacterium columnare, Flavobacterium psychrophilum, Aeromonas salmonicida, Aeromonas hydrophila, Vibrio anguillarum, Vibrio harveyi, and Vibrio parahaemolyticus, and their potential to be used as a therapeutic agent has been studied by several researchers. This review highlights the potential, strategy, mode of application, dosing, advantages, and limitations of bacteriophage therapy in aquaculture and its way forward.

Dual estrogenic regulation of the nuclear progestin receptor and spermatogonial renewal during gilthead seabream (Sparus aurata) spermatogenesis

Studies in teleosts suggest that progestins have crucial functions during early spermatogenesis. However, the role of the different progestin receptors in these mechanisms is poorly understood. In this work, we investigated the expression pattern and hormonal regulation of the classical nuclear progestin receptor (Pgr) in the gilthead seabream at three different stages of spermatogenesis: the resting (postspawning) phase, onset of spermatogenesis, and spermiation. Immunolocalization experiments using a seabream specific Pgr antibody revealed that the receptor was expressed in Sertoli and Leydig cells, and also in a subset of spermatogonia type A, throughout spermatogenesis. Short-term treatment of testis explants with 17β-estradiol (E2) increased pgr mRNA expression at all stages, while the progestin 17α,20β-dihydroxy-4-pregnen-3-one (17,20βP) had the opposite effect. At the resting stage, Sertoli cell Pgr expression was positively correlated with the occurrence of proliferating spermatogonia type A in the tubules, and both processes were incremented in vitro by E2 likely through the estrogen receptor alpha (Era) expressed in Sertoli and Leydig cells. In contrast, treatment with 17,20βP downregulated Pgr expression in somatic cells. The androgen 11-ketotestosterone (11-KT) upregulated pgr expression in Leydig cells and promoted the proliferation of mostly spermatogonia type B, but only during spermiation. No relationship between the changes in the cell type-specific expression of the Pgr with the entry into meiosis of germ cells was found. These data suggest a differential steroid regulation of Pgr expression during seabream spermatogenesis and the potential interplay of the E2/Era and 17,20βP/Pgr pathways for the maintenance of spermatogonial renewal rather than entry into meiosis.

Gel properties of sutchi catfish (Pangasius hypophthalmus) surimi as affected by selected washing process and number of washing cycles

The gel properties of sutchi catfish surimi prepared by conventional washing and alkaline–saline washing method were studied for four washing cycles. Decrease (p < 0.05) in myoglobin content was found in alkaline washing process compared to conventional washing at each washing cycle. The highest hardness, breaking force and deformation was observed in gels prepared from alkaline–saline washing method. Whiteness in conventional washed surimi gels increased non-significantly (p < 0.05) compared to alkaline–saline-washed surimi gels. Protein bands on Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated that the protein extractability was more in alkaline–saline washing and disappearance of bands in conventional washing method was observed between 116 and 45 kDa indicating less yield of protein.

The cellular localization and redistribution of multiple aquaporin paralogs in the spermatic duct epithelium of a maturing marine teleost

Aquaporin‐mediated fluid transport in the mammalian efferent duct and epididymis is believed to play a role in sperm maturation and concentration. In fish, such as the marine teleost gilthead seabream (Sparus aurata), the control of fluid homeostasis in the spermatic duct seems also to be crucial for male fertility, but no information exists on the expression and distribution of aquaporins. In this study, reverse transcriptase‐polymerase chain reaction and immunoblotting analyses, employing available and newly raised paralog‐specific antibodies for seabream aquaporins, indicate that up to nine functional aquaporins, Aqp0a, ‐1aa, ‐1ab, ‐3a, ‐4a, ‐7, ‐8bb, ‐9b and ‐10b, are expressed in the spermatic duct. Immunolocalization of the channels in the resting spermatic duct reveals that Aqp0a, ‐1aa, ‐4a, ‐7 and ‐10b are expressed in the monolayered luminal epithelium, Aqp8b and ‐9b in smooth muscle fibers, and Aqp1ab and ‐3a in different interstitial lamina cells. In the epithelial cells, Aqp0a and ‐1aa are localized in the short apical microvilli, and Aqp4a and ‐10b show apical and basolateral staining, whereas Aqp7 is solely detected in vesicular compartments. Upon spermiation, an elongation of the epithelial cells sterocilia, as well as the folding of the epithelium, is observed. At this stage, single‐ and double‐immunostaining, using two aquaporin paralogs or the Na+/K+‐ATPase membrane marker, indicate that Aqp1ab, ‐3a, ‐7, ‐8bb and ‐9b staining remains unchanged, whereas in epithelial cells Aqp1aa translation is supressed, Aqp4a internalizes, and Aqp0a and ‐10b accumulate in the apical, lateral and basal plasma membrane. These findings uncover a cell type‐ and region‐specific distribution of multiple aquaporins in the piscine spermatic duct, which shares conserved features of the mammalian system. The data therefore suggest that aquaporins may play different roles in the regulation of fluid homeostasis and sperm maturation in the male reproductive tract of fish.

Genetic diversity and demographic history of the giant river catfish Sperata seenghala inferred from mitochondrial DNA markers.

Abstract The giant river catfish Sperata seenghala has huge demand in South Asian countries due to its low number of intramuscular bones and nutritive value. However, the culture practises for this fish have not been standardized and the current demand for this fish is being met by capture fisheries only. Unregulated and indiscriminate fishing would lead overexploitation of fish stocks subsequently stock depletion. Genetic diversity between populations would give insight about population structure and demography. In the present study, S. seenghala stocks from three rivers, namely Ganga, Brahmaputra and Mahanadi were characterized using cytochrome b gene and D-loop region. Moderate to high haplotype diversity and low nucleotide diversity values were observed in all populations. Analysis of molecular variance and pairwise FST values showed significant genetic differentiation among populations. Patterns of diversity, haplotype networks and mismatch distribution strongly suggest a historical influence on the genetic structure of S. seenghala populations. S. seenghala stocks from these three rivers are genetically distinct units and management measures should be formulated separately for each population.