Alpha2-macroglobulin from an Atlantic shrimp: biochemical characterization, sub-cellular localization and gene expression upon fungal challenge.

In this study, we report on the isolation and characterization of an alpha2-macroglobulin (α2M) from the plasma of the pink shrimp Farfantepenaeus paulensis, its sub-cellular localization and transcriptional changes after infection by fungi. The molecular mass of the α2M was estimated at 389 kDa by gel filtration and 197 kDa by SDS-PAGE, under reducing conditions, suggesting that α2M from F. paulensis consists of two identical sub-units, covalently linked by disulphide bonds. The N-terminal amino acid sequence of the α2M from F. paulensis was very similar to those of other penaeid shrimps, crayfish and lobster (70-90% identity) and to a less extent with that of freshwater prawn (40% identity). A monoclonal antibody raised against the Marsupenaeus japonicus α2M made it possible to demonstrate that α2M of F. paulensis is stored in the vesicles of the shrimp granular hemocytes (through immunogold assay). Quantitative real-time PCR (qPCR) analysis showed that α2M mRNA transcripts significantly increased 24 h after an experimental infection with the shrimp pathogen Fusarium solani and it returned to the basal levels at 48 h post-injection. This is the first report on a α2M characterization in an Atlantic penaeid species and its expression profile upon a fungal infection.

Diet supplemented with probiotic for Nile tilapia in polyculture system with marine shrimp.

The aim of this study was to assess the effect of a probiotic (Lactobacillus plantarum) supplemented diet on Nile tilapia (Oreochromis niloticus) in a polyculture system with marine shrimp (Litopenaeus vannamei) as regards culture performance, hematology, and gut bacterial microbiota. Ten 20-m² pens were arranged in one earthen pond and stocked with 2 fish (41.9 g) m(-2) and 10 shrimp (2.3 g) m(-2), in total of 40 Nile tilapias and 200 shrimp per experimental unit. Tilapia groups in five of the experimental units were fed a commercial diet supplemented with L. plantarum and the other five with an unsupplemented commercial diet (control). After 12 weeks of culture, the tilapia groups fed the probiotic-supplemented diet presented values 13.6, 7.5, and 7.1% higher for feed efficiency, yield, and final weight, respectively. Viable culturable heterotrophic bacteria counts were reduced, and the number of lactic acid bacteria was increased in the gut of fish and shrimp fed the probiotic-supplemented diet. Hematological analyses showed higher number of thrombocytes and leukocytes in tilapia fed the supplemented diet. L. plantarum utilized in this study colonized the gut of tilapia and shrimp and resulted in reduced number of total bacteria and increased tilapia final weight and feed efficiency.

Combining a probiotic with organic salts presents synergistic in vitro inhibition against aquaculture bacterial pathogens

ABSTRACT This study aimed to evaluate 1) the in vitro effect of organic salts on the growth of the probiotic Lactobacillus plantarum and then 2) the combined use of a probiotic with organic salts on the in vitro inhibition of V. alginolyticus, A. hydrophila, E. coli, P. aeruginosa, and S. agalactiae. In vitro tests were performed with eight different organic salts, including butyrate, propionate, succinate, citrate, formate, fumarate, glutamate, and acetate, at two pH values (6.2 and 7.1) to determine their effect on the growth kinetics of L. plantarum. In addition, each organic salt was tested alone and in combination with L. plantarum to evaluate the inhibitory effect against the pathogenic bacteria noted above in either condition. Sodium citrate and formate inhibited the growth of L. plantarum, but sodium glutamate, succinate and fumarate stimulated it. Sodium propionate, butyrate, and acetate did not affect probiotic growth at all. Inhibition against all pathogens was significantly higher in the presence of the probiotic and lower pH. Comparing all organic salts at the two pH values, butyrate, acetate, and propionate exhibited more inhibition against V. alginolyticus than the others, while propionate had higher inhibition against A. hydrophila, E. coli, P. aeruginosa, and fumarate successfully inhibited S. agalactiae. Based on these results, it can be concluded that organic salts showed better in vitro inhibition against the aquaculture pathogenic bacteria tested when combined with the probiotic L. plantarum.

Cultivation of juvenile fat snook (Centropomus parallelus Poey, 1860) fed probiotic in laboratory conditions

The objective of this study was to investigate the growth of juvenile fat snook (Centropomus parallelus) in laboratory conditions when fed a diet supplemented with the probiotic Lactobacillus plantarum. Changes in the intestinal flora, haematological parameters and growth performance were assessed using 180 fishes (54.2 ± 13.4 g each). The fishes were subjected to two treatments divided into six cages: 1) feed supplemented with probiotic, and 2) feed without probiotic (control). The temperature, dissolved oxygen and salinity were maintained at 25 ± 1 ° C, 4.0 mg.L-1 and 33 ‰, respectively. After 10 weeks of culture, the fishes fed probiotic had reduced viable culturable heterotrophic bacteria and Vibrio spp. and increased lactic acid bacteria in the intestinal tract, as well as a higher number of thrombocytes, leukocytes and lymphocytes in the blood. No significant difference was observed in the growth, survival or body composition, but the hepatosomatic index was significantly higher in the fishes fed with probiotic and control.