Immune and bacterial toxin genes expression in different giant tiger prawn, Penaeus monodon post-larvae stages following AHPND-causing strain of Vibrio parahaemolyticus challenge

Acute Hepatopancreatic Necrosis Disease (AHPND), a disease caused by Vibrio parahaemolyticus (V-PAHPND), kills Penaeid shrimps worldwide, resulting in severe economic losses during aquaculture. To further understand how Penaeus monodon post-larvae (PL) respond towards infection of this pathogenic bacterium, the expression of several important immune and bacterial toxin genes in three stages of P. monodon PL (PL15, PL30 and PL45) upon V-PAHPND challenge, were determined. A 20-hrs challenge test with 2.7 x 10(7) cfu ml(-1) of V-PADPND resulted 81, 65 and 1.7% mortality respectively for PL30, PL15 and PL45, indicating that PL30 was most vulnerable to V-PADPNEP The immune response of shrimp PL at this stage was robust, with Toll-like receptor (TLR), prophenoloxidase (proPO), lysozyme (lyso) and penaeidin (PEN) augmented approximately 10.7, 4.7, 6.5 and 3.2-fold, respectively. The expression initiated at one hour post-infection (h.p.i), peaked at 16 h.p.i and 20 h.p.i, and decreased at 18 h.p.i, indicating the crucial involvement of these immune related genes in the defence and recovery of the first-line defence mechanisms during V-PADPND infection. This work also revealed that toxR gene represents a good indicator gene for Vibrio detection whereas PIR A, for V-PADPND pathogenicity determination of P. monodon. Overall, these findings provided novel insights into the immune response and V-PADPND No susceptibility of different P. monodon PL stages during infection, with outcomes potentially useful in enhancing the application of health therapy and biosecured aquaculture practices to minimize the damaging risk of AHPND towards sustainable production of P. monodon

PROBIOTICS BACTERIA AS QUORUM SENSING DEGRADER CONTROL Aeromonas hydrophila PATHOGENICITY IN CULTURED RED HYBRID TILAPIA

Quorum sensing (QS) is the interaction of bacteria cell-to-cell to regulate various bacterial functions, including bacterial virulence. It has been suggested that QS interruption is an anti-infective strategy to combat diseases in aquaculture. This research was conducted to isolate the potential probiotics bacteria as QS degrader from the fish gut and investigate its efficiency in reducing Aeromonas hydrophila pathogenicity by in vitro and in vivo assay. In this study, three isolates from the fish gut were able to degrade N-acyl homoserine lactone (AHL), one of the QS signals of A. hydrophila. Based on 16S rDNA sequence analysis, isolate CPi12 was identified as Klebsiella sp., CBa5 and CBa7 were identified as Enterobacter tabaci. These isolates were co-cultured with A.hydrophila for five days. Results revealed that all isolates could decrease the AHL production of A. hydrophila but did not affect the growth of the pathogen. In vivo assay results showed that isolate CPi12 reduced the pathogenicity of A.hydrophila against tilapia with a significantly higher survival rate (p<0.05) of fish in the CPi12-fed group than the control group. Meanwhile, isolate CBa7 was significant (p<0.05) for growth performance, including specific growth rate (SGR), weight gain (WG), feed conversion ratio (FCR), mean weight gain (MWG), and average daily growth (ADG) among whole treatment and control group. These results displayed that the probiotics bacteria as QS degrader isolated from the fish gut could control the pathogenicity of Aeromonas hydrophila. It has been proposed that QS degrader bacteria might be an alternative solution for disease control

A Review of Marine Viruses in Coral Ecosystem

Coral reefs are among the most biodiverse biological systems on earth. Corals are classified as marine invertebrates and filter the surrounding food and other particles in seawater, including pathogens such as viruses. Viruses act as both pathogen and symbiont for metazoans. Marine viruses that are abundant in the ocean are mostly single-, double stranded DNA and single-, double stranded RNA viruses. These discoveries were made via advanced identification methods which have detected their presence in coral reef ecosystems including PCR analyses, metagenomic analyses, transcriptomic analyses and electron microscopy. This review discusses the discovery of viruses in the marine environment and their hosts, viral diversity in corals, presence of virus in corallivorous fish communities in reef ecosystems, detection methods, and occurrence of marine viral communities in marine sponges

Effects of host gut-derived probiotic bacteria on gut morphology, microbiota composition and volatile short chain fatty acids production of Malaysian Mahseer Tor tambroides

Three host-associated probiotics (Bacillus sp. AHG22, Alcaligenes sp. AFG22, and Shewanella sp. AFG21) were isolated from the gastrointestinal tract of Tor tambroides, and their effects were evaluated on gut morphology, microbiota composition and volatile short chain fatty acids (VSCFAs) production of the same species. A control diet (40% crude protein and 10% lipid) was formulated, and three different probiotic supplemented diets were prepared by immersing the control diet in each host-derived isolated probiotic, suspended in sterile phosphate buffered saline (PBS), to achieve concentration at 1.0 × 108 CFU g−1 feed. Triplicate groups of T. tambroides juveniles (1.39 ± 0.06 g) were stocked in twelve glass aquaria (100 L capacity) with stocking density of 20 individuals per aquarium. The feed was applied twice daily at 3.0% of the body weight per day for 90 days. The intake of probiotics drastically modified the gut microbiota composition. The average number of OTUs, Shannon index and Margalef species richness were significantly higher in host-associated probiotic treatments compared to the control. A significant increase of lipolytic, proteolytic and cellulolytic bacterial number were observed in the gastrointestinal tracts of T. tambroides fed the diets supplemented with Alcaligenes sp. AFG22 compared to the control. Villus length, villus width and villus area were significantly higher in T. tambroides juveniles fed the diet supplemented with Alcaligenes sp. AFG22. Acetate and butyrate were detected as main VSCFA production in the gastrointestinal tract of T. tambroides. Acetate and total VSCFAs production in Alcaligenes sp. AFG22 supplemented treatment was significantly higher than control. These results indicate that host-derived probiotics, especially Alcaligenes sp. has a significant potential as an important probiotic to enhance the nutrients utilization and metabolism through increasing gut surface area and VSCFAs production, and adjusting gut microbiota balance of T. tambroides juveniles

Skim-sequencing based genotyping reveals genetic divergence of the wild and domesticated population of black tiger shrimp (<i>Penaeus monodon</i>) in the Indo-Pacific region

The domestication of a wild-caught aquatic animal is an evolutionary process, which results in genetic discrimination at the genomic level in response to strong artificial selection. Although black tiger shrimp (Penaeus monodon) is one of the most commercially important aquaculture species, a systematic assessment of genetic divergence and structure of wild-caught and domesticated broodstock populations of the species is yet to be documented. Therefore, we used skim sequencing (SkimSeq) based genotyping approach to investigate the genetic structure of 50 broodstock individuals of P. monodon species, collected from five sampling sites (n = 10 in each site) across their distribution in Indo-Pacific regions. The wild-caught P. monodon broodstock population were collected from Malaysia (MS) and Japan (MJ), while domesticated broodstock populations were collected from Madagascar (MMD), Hawaii, HI, USA (MMO), and Thailand (MT). After various filtering process, a total of 194,259 single nucleotide polymorphism (SNP) loci were identified, in which 4983 SNP loci were identified as putatively adaptive by the pcadapt approach. In both datasets, pairwise FST estimates high genetic divergence between wild and domesticated broodstock populations. Consistently, different spatial clustering analyses in both datasets categorized divergent genetic structure into two clusters: (1) wild-caught populations (MS and MJ), and (2) domesticated populations (MMD, MMO and MT). Among 4983 putatively adaptive SNP loci, only 50 loci were observed to be in the coding region. The gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses suggested that non-synonymous mutated genes might be associated with the energy production, metabolic functions, respiration regulation and developmental rates, which likely act to promote adaptation to the strong artificial selection during the domestication process. This study has demonstrated the applicability of SkimSeq in a highly duplicated genome of P. monodon specifically, across a range of genetic backgrounds and geographical distributions, and would be useful for future genetic improvement program of this species in aquaculture

Image_1_Understanding the effects of salinity and Vibrio harveyi on the gut microbiota profiles of Litopenaeus vannamei.png

Increasing evidence have revealed a positive correlation between gut microbiota and shrimp health, in which a healthy shrimp gut consists of a complex and stable microbial community. Given that both abiotic and biotic factors constantly regulate shrimp gut microbiota, any changes affecting the levels of these factors could cause modification to the gut microbiota assemblage. The goal of this study was to explore the effects of salinity levels and pathogenic Vibrio harveyi infection on the diversity, structure, composition, interspecies interaction, and functional pathways of Litopenaeus vannamei gut microbiota. Juvenile shrimp were cultured at 5 ppt, 20 ppt, and 30 ppt for two months prior to Vibrio harveyi infection. After pathogenic V. harveyi challenge test, genomic DNA was isolated from the shrimp gut, and subjected to the 16S rRNA metagenomic sequencing analysis. We observed that gut microbiota diversity of shrimp cultured at 5 ppt and 30 ppt were lower than those cultured at 20 ppt after exposure to V. harveyi infection, suggesting that shrimp cultured at the two former salinity levels were more susceptible to V. harveyi infection. Network analysis also showed that shrimp cultured at 20 ppt exhibit a more stable bacterial network with complex interspecies interaction, even after induced by V. harveyi. Moreover, the presence of a high number of beneficial bacteria such as Pseudoruegeria, Rhodovulum, Ruegeria, Shimia and Lactobacillus in shrimp cultured at 20 ppt might have played a role in inhibiting the growth of V. harveyi and other potentially pathogenic bacteria. Besides, bacterial functional pathway prediction has also shown that metabolic pathways such as phenylalanine metabolism, glycine, serine and threonine metabolism, starch and sucrose metabolism, glyoxylate and dicarboxylate metabolism, carbon metabolism and biofilm formation process were significantly higher in shrimp cultured at 20 ppt. Collectively, our results suggested that 20 ppt is an optimal salinity that suppresses the growth of V. harveyi and potential pathogenic bacteria in the shrimp gut, which could possibly minimize the risk of pathogenic infection for sustainable production of healthy shrimp.</p

Image_4_Understanding the effects of salinity and Vibrio harveyi on the gut microbiota profiles of Litopenaeus vannamei.png

Increasing evidence have revealed a positive correlation between gut microbiota and shrimp health, in which a healthy shrimp gut consists of a complex and stable microbial community. Given that both abiotic and biotic factors constantly regulate shrimp gut microbiota, any changes affecting the levels of these factors could cause modification to the gut microbiota assemblage. The goal of this study was to explore the effects of salinity levels and pathogenic Vibrio harveyi infection on the diversity, structure, composition, interspecies interaction, and functional pathways of Litopenaeus vannamei gut microbiota. Juvenile shrimp were cultured at 5 ppt, 20 ppt, and 30 ppt for two months prior to Vibrio harveyi infection. After pathogenic V. harveyi challenge test, genomic DNA was isolated from the shrimp gut, and subjected to the 16S rRNA metagenomic sequencing analysis. We observed that gut microbiota diversity of shrimp cultured at 5 ppt and 30 ppt were lower than those cultured at 20 ppt after exposure to V. harveyi infection, suggesting that shrimp cultured at the two former salinity levels were more susceptible to V. harveyi infection. Network analysis also showed that shrimp cultured at 20 ppt exhibit a more stable bacterial network with complex interspecies interaction, even after induced by V. harveyi. Moreover, the presence of a high number of beneficial bacteria such as Pseudoruegeria, Rhodovulum, Ruegeria, Shimia and Lactobacillus in shrimp cultured at 20 ppt might have played a role in inhibiting the growth of V. harveyi and other potentially pathogenic bacteria. Besides, bacterial functional pathway prediction has also shown that metabolic pathways such as phenylalanine metabolism, glycine, serine and threonine metabolism, starch and sucrose metabolism, glyoxylate and dicarboxylate metabolism, carbon metabolism and biofilm formation process were significantly higher in shrimp cultured at 20 ppt. Collectively, our results suggested that 20 ppt is an optimal salinity that suppresses the growth of V. harveyi and potential pathogenic bacteria in the shrimp gut, which could possibly minimize the risk of pathogenic infection for sustainable production of healthy shrimp.</p

Image_5_Understanding the effects of salinity and Vibrio harveyi on the gut microbiota profiles of Litopenaeus vannamei.png

Increasing evidence have revealed a positive correlation between gut microbiota and shrimp health, in which a healthy shrimp gut consists of a complex and stable microbial community. Given that both abiotic and biotic factors constantly regulate shrimp gut microbiota, any changes affecting the levels of these factors could cause modification to the gut microbiota assemblage. The goal of this study was to explore the effects of salinity levels and pathogenic Vibrio harveyi infection on the diversity, structure, composition, interspecies interaction, and functional pathways of Litopenaeus vannamei gut microbiota. Juvenile shrimp were cultured at 5 ppt, 20 ppt, and 30 ppt for two months prior to Vibrio harveyi infection. After pathogenic V. harveyi challenge test, genomic DNA was isolated from the shrimp gut, and subjected to the 16S rRNA metagenomic sequencing analysis. We observed that gut microbiota diversity of shrimp cultured at 5 ppt and 30 ppt were lower than those cultured at 20 ppt after exposure to V. harveyi infection, suggesting that shrimp cultured at the two former salinity levels were more susceptible to V. harveyi infection. Network analysis also showed that shrimp cultured at 20 ppt exhibit a more stable bacterial network with complex interspecies interaction, even after induced by V. harveyi. Moreover, the presence of a high number of beneficial bacteria such as Pseudoruegeria, Rhodovulum, Ruegeria, Shimia and Lactobacillus in shrimp cultured at 20 ppt might have played a role in inhibiting the growth of V. harveyi and other potentially pathogenic bacteria. Besides, bacterial functional pathway prediction has also shown that metabolic pathways such as phenylalanine metabolism, glycine, serine and threonine metabolism, starch and sucrose metabolism, glyoxylate and dicarboxylate metabolism, carbon metabolism and biofilm formation process were significantly higher in shrimp cultured at 20 ppt. Collectively, our results suggested that 20 ppt is an optimal salinity that suppresses the growth of V. harveyi and potential pathogenic bacteria in the shrimp gut, which could possibly minimize the risk of pathogenic infection for sustainable production of healthy shrimp.</p