Analysis of microbiota in the stomach and midgut of two penaeid shrimps during probiotic feeding.

In mammals, the intestine harbors numerous bacteria that play an important role in health. Intestinal microbiota have also been thought to be an important factor in the health of shrimp. However, the barrier systems of the digestive tracts of shrimp seem to be different from those of mammals. In this study, we analyzed the bacterial composition in the stomach and midgut of two species of shrimp during administration of a probiotic, Bacillus amyloliquefaciens strain TOA5001 by analysis of 16S rRNA genes with Illumina sequencing technology. Whiteleg shrimp Litopenaeus vannamei were observed under laboratory conditions and kuruma shrimp Marsupenaeus japonicus were observed in an aquaculture farm. The diversities of bacteria in the stomachs of both shrimps were significantly higher than those in the midgut. Also, the microbiota changed during probiotic feeding. Feeding whiteleg shrimp the probiotic after being challenged with an acute hepatopancreatic necrosis disease (AHPND)-causing strain of Vibrio parahaemolyticus increased their survival compared to the control group, which suggested that the probiotic prevented AHPND. These results appear to show that a probiotic can affect the microbiota throughout digestive tract of penaeid shrimps and that probiotic can have a role in preventing disease.

Identification of an anti-lipopolysaccharide factor AV-R isoform (LvALF AV-R) related to Vp_PirAB-like toxin resistance in Litopenaeus vannamei.

Acute hepatopancreatic necrosis disease (AHPND) is a shrimp farming disease, caused by the pathogenic Vibrio parahaemolyticus carrying a plasmid encoding Vp_PirAB-like toxins. Formalin-killed cells of V. parahaemolyticus AHPND-causing strain D6 (FKC-VpD6) were used to select Vp_PirAB-like toxin-resistant Litopenaeus vannamei by oral administration. Stomach and hepatopancreas tissues of shrimps that survived for one week were subjected to RNA sequencing. Differentially expressed genes (DEGs) between surviving shrimp, AHPND-infected shrimp, and normal shrimp were identified. The expressions of 10 DEGs were validated by qPCR. Only one gene (a gene homologous to L. vannamei anti-lipopolysaccharide factor AV-R isoform (LvALF AV-R)) was expressed significantly more strongly in the hepatopancreas of surviving shrimp than in the other groups. Significantly higher expression of LvALF AV-R was also observed in shrimp that survived two other trials of FKC-VpD6 selection. Recombinant ALF AV-R bound to LPS, PGN, Gram-negative bacteria, and some Gram-positive bacteria in ELISAs. ALF AV-R recombinant protein did not interact with native Vp_PirAB-like toxin in an ELISA or a Far-Western blot. For L. vannamei orally fed ALF AV-R protein for 3 days, the survival rate following challenge with VpD6-immersion was not significantly different from that of shrimp fed two control diets. These results suggest that LvALF AV-R expression was induced in the hepatopancreas of shrimp in response to the presence of Vp_PirAB-like toxin, although other factors might also be involved in the resistance mechanism.

Draft Genome Sequences of Six Strains of Vibrio parahaemolyticus Isolated from Early Mortality Syndrome/Acute Hepatopancreatic Necrosis Disease Shrimp in Thailand.

Some strains of Vibrio parahaemolyticus cause acute hepatopancreatic necrosis disease (AHPND) in shrimp. We sequenced 3 AHPND and 3 non-AHPND strains and found that all of them lacked the pathogenicity island relevant to human infection. A unique sequence encoding a type IV pilus/type IV secretion system was found in 3 AHPND strains.