Proteomics analysis reveals a critical role for the WSSV immediate-early protein IE1 in modulating the host prophenoloxidase system.

White spot syndrome virus (WSSV) is a large, enveloped, double-stranded DNA virus that threatens shrimp aquaculture worldwide. So far, the mechanisms of WSSV-host interactions are ill-defined. Recent studies have revealed that IE1, an immediate-early protein of WSSV, is a multifunctional modulator implicated in virus-host interactions. In this study, the functions of IE1 were further explored by identifying its interacting proteins using GST-pull down and mass spectrometry analysis. A total of 361 host proteins that potentially bind to IE1 were identified. Bioinformatics analysis revealed that the identified IE1-interactors wereinvolved in various signaling pathways such as prophenoloxidase (proPO) system, PI3K-AKT, and MAPK. Among these, the regulatory role of IE1 in shrimp proPO system was further studied. The Co-immunoprecipitation results confirmed that IE1 interacted with the Ig-like domain of Penaeus vannamei proPO or proPO-like protein (hemocyanin). Additionally, we found that knockdown of IE1 reduced viral genes expression and viral loads and increased the hemocytes' PO activity, whereas recombinant IE1 protein inhibited the PO activity in a dose-dependent manner. Finally, we demonstrated that WSSV could suppress the hemocytes' PO activity at the early infection stage. Collectively, our current data indicate that IE1 is a novel viral regulator that negatively modulates the shrimp proPO system.

Penaeicolahalotolerans gen. nov., sp. nov., a novel bacterium of the family Cyclobacteriaceae isolated from a shrimp pond.

A Gram-stain-negative, non-motile, rod-shaped, aerobic bacterium (designated as LMIT005T) was isolated from shrimp ponds in Shantou, China. The new isolate was characterized taxonomically using a polyphasic approach. Based on 16S rRNA gene sequence analysis, strain LMIT005T was found to be affiliated with the family Cyclobacteriaceae of the order Cytophagales while appearing as a distinct lineage. The 16S rRNA gene sequence similarity between strain LMIT005T and Algoriphagus yeomjeoni KCTC 12309T, the closest type strain in the family, was 91.3 %. Strain LMIT005T grew optimally at 25 °C, pH 7 and in the presence of 2.0 % (w/v) NaCl. The DNA G+C content (data from genome sequence) was 40.5 mol%. Compared with reference strain A. yeomjeoni KCTC 12309T, the average nucleotide identity (ANI) of LMIT005T was 70 %. The sole respiratory quinone of LMIT005T was menaquinone (MK-7), and the major fatty acids were summed feature 3 (C16 : 1 ω6c / C16 : 1 ω7c). The polar lipids of strain LMIT005T were mainly composed of phosphatidylethanolamine, phosphatidylcholine, two unidentified amino lipids, two unidentified lipids, one unidentified glycolipid and one unidentified phospholipid. The draft genome of strain LMIT005T comprised 3 089 781 bp (3.09 Mb) nucleotides and 2773 genes. Antimicrobial resistant-related genes (blal, mexA, and mexb) were annotated in the genome of strain LMIT005T, which indicated that it might be able to resist ß-lactam antibiotics. This was further verified by antimicrobial resistant test. Given its distinct genomic, morphological, and physiological differences from previously described type strains, strain LMIT005T is proposed as a representative of a novel genus of the family Cyclobacteriaceae, with the name Penaeicola halotolerans gen. nov., sp. nov. The type strain is LMIT005T (=KCTC 82616T=CICC 25047T).

Effects of dietary lipid sources on the intestinal microbiome and health of golden pompano (Trachinotus ovatus).

Replacement of fish oil (FO) with vegetable oils (VO) in diets is economically desirable for the sustainable development of the aquaculture industry. However, inflammation provoked by FO replacement limited its widely application in fish industry. In order to understand the mechanism of VO-induced inflammation, this study investigated the impact of different dietary vegetable oils on the intestinal health and microbiome in carnivorous marine fish golden pompano (Trachinotus ovatus). Three diets supplemented with fish oil (FO, rich in long-chain polyunsaturated fatty acids), soybean oil (SO, rich in 18:2n-6) and linseed oil (LO, rich in 18:3n-3), respectively, were fed on juvenile golden pompano for 8 weeks, and the intestinal histology, digestive enzymes activities, immunity and antioxidant indices as well as intestinal microbiome were determined. The results showed that dietary SO significantly impaired intestinal health, and decreased the number and height of intestinal folds, and muscle thickness, as well as the zonula occludens-1 (zo-1) mRNA expression in intestine. Moreover, the two dietary VO significantly decreased the amylase and lipase activities in intestine, and reduced the trypsin activity in the dietary SO group. Furthermore, the two VO diets increased intestinal acid phosphatase (ACP) activity, while intestinal lysozyme (LZM) activity and serum diamine oxidase (DAO) activity in the SO group were also significantly increased (P < 0.05). Analysis of the intestinal microbiota showed that the two VO diets significantly increased the abundance of intestinal potentially pathogenic bacteria (Mycoplasma and Vibrio) and decreased proportions of intestinal probiotics (Bacillus and Lactococcus), especially in the dietary SO group. These results indicate that complete replacement of FO with VO in diets would induce intestinal inflammation and impair intestinal function, which might be due to changes in intestinal microbiota profiles, and that dietary SO would have a more negative effect compared to dietary LO on intestinal health in T. ovatus.