Quantitative prediction of shrimp disease incidence via the profiles of gut eukaryotic microbiota

Dinotefuran exposure alters biochemical, metabolomic, gut microbiome, and growth responses in decapoda pacific white shrimp Penaeus vannamei

Dinotefuran, a neonicotinoid insecticide, may impact nontarget organisms such as Decapoda P. vannamei shrimp with nervous systems similar to insects. Exposing shrimp to low dinotefuran concentrations (6, 60, and 600 μg/L) for 21 days affected growth, hepatosomatic index, and survival. Biomarkers erythromycin-N-demethylase, alanine aminotransferase, and catalase increased in all exposed groups, while glutathione S-transferase is the opposite; aminopyrin-N-demethylase, malondialdehyde, and aspartate aminotransferase increased at 60 and 600 μg/L. Concentration-dependent effects on gut microbiota altered the abundance of bacterial groups, increased potentially pathogenic and oxidative stress-resistant phenotypes, and decreased biofilm formation. Gram-positive/negative microbiota changed significantly. Metabolite differences between the exposed and control groups were identified using mass spectrometry and KEGG pathway enrichment. N-acetylcystathionine showed potential as a reliable dinotefuran metabolic marker. Weighted correlation network analysis (WGCNA) results indicated high connectivity of cruecdysone in the metabolite network and significant enrichment at 600 μg/L dinotefuran. The WGCNA results revealed a highly significant negative correlation between two key metabolites, caldine and indican, and the gut microbiota within co-expression modules. Overall, the risk of dinotefuran exposure to non-target organisms in aquatic environments still requires further attention.

Covariation between microeukaryotes and bacteria associated with Planorbidae snails

Background

Microbial communities associated with macroorganisms might affect host physiology and homeostasis. Bacteria are well studied in this context, but the diversity of microeukaryotes, as well as covariations with bacterial communities, remains almost unknown.

Methods

To study microeukaryotic communities associated with Planorbidae snails, we developed a blocking primer to reduce amplification of host DNA during metabarcoding analyses. Analyses of alpha and beta diversities were computed to describe microeukaryotes and bacteria using metabarcoding of 18S and 16S rRNA genes, respectively.

Results

Only three phyla (Amoebozoa, Opisthokonta and Alveolata) were dominant for microeukaryotes. Bacteria were more diverse with five dominant phyla (Proteobacteria, Bacteroidetes, Tenericutes, Planctomycetes and Actinobacteria). The composition of microeukaryotes and bacteria were correlated for the Biomphalaria glabrata species, but not for Planorbarius metidjensis. Network analysis highlighted clusters of covarying taxa. Among them, several links might reflect top-down control of bacterial populations by microeukaryotes, but also possible competition between microeukaryotes having opposite distributions (Lobosa and Ichthyosporea). The role of these taxa remains unknown, but we believe that the blocking primer developed herein offers new possibilities to study the hidden diversity of microeukaryotes within snail microbiota, and to shed light on their underestimated interactions with bacteria and hosts.

Toxicity of the microcystin-producing cyanobacteria Microcystis aeruginosa to shrimp Litopenaeus vannamei

Microcystis aeruginosa is reported to cause cyanobacterial blooms in shrimp breeding ponds, which can result in significant shrimp mortality. However, the toxic effects of M. aeruginosa on Litopenaeus vannamei are still not completely understood. In this paper, the toxicity of M. aeruginosa cells to L. vannamei was examined, and the toxic components in the cells were analyzed through high-pressure liquid chromatography (HLPC). In addition, the immune response of shrimp to the M. aeruginosa cell extract was assessed by measuring the activity of immune-related enzymes, as well as the transcription of the relevant genes. The results showed that M. aeruginosa cells, extract and cell-free cultured medium resulted in a 100%, 98.3%, and 1.7% mortality rate in shrimp, respectively. HPLC analysis results revealed the presence of microcystin-LR (MC-LR) at a concentration of 190.40 mg/kg of cells. In addition, the activity and gene transcription of two immune related enzymes, SOD and LZM, were both significantly reduced in shrimp hepatopancreas (p < 0.05) after injection with extract. However, reduced glutathione (GSH) content was slightly increased, but the ratio of GSH to GSSG decreased. The transcription of gst gene function as detoxification, was significantly downregulated (p < 0.05). The results demonstrated that M. aeruginosa cell extract was highly toxic to L. vannamei, and exerted a negative effect on shrimp immunity including reduction of antioxidant capacity, antibacterial activity and detoxification activity, due to toxins including microcystin-LR.

The emerging pathogen Enterocytozoon hepatopenaei drives a degenerative cyclic pattern in the hepatopancreas microbiome of the shrimp (Penaeus vannamei)

The microsporidian Enterocytozoon hepatopenaei (EHP) is an emerging pathogen that causes substantial economic losses in shrimp (Penaeus spp.) aquaculture worldwide. To prevent diseases in shrimp, the manipulation of the gut microbiota has been suggested. However, prior knowledge of the host-microbiome is necessary. We assessed the modulation of the microbiome (bacteria/fungi) and its predicted functions over the course of disease progression in shrimp experimentally challenged with EHP for 30 days using high throughput 16S rRNA and ITS amplicon sequencing. Infection grade was assessed for the first time by quantitative digital histopathology. According to the infection intensity, three disease-stages (early/developmental/late) were registered. During the early-stage, EHP was not consistently detected, and a high diversity of potentially beneficial microorganisms related to nutrient assimilation were found. In the development-stage, most of the shrimp start to register a high infection intensity related to a decrease in beneficial microorganisms and an increase in opportunistic/pathogenic fungi. During late-stage, animals displayed different infection intensities, showed a displacement of beneficial microorganisms by opportunistic/pathogenic bacteria and fungi related to pathogen infection processes and depletion of energetic reserves. The degenerative cyclic pattern of EHP infection and its effects on beneficial microorganisms and beneficial functions of the shrimp hepatopancreas microbiome are discussed.

Combined toxic effects of thiamethoxam on intestinal flora, transcriptome and physiology of Pacific white shrimp Litopenaeus vannamei

The environmental accumulation of thiamethoxam has increasingly become a risk for the health of aquatic animals, especially crustacean species in the same phylum as the target pests. The lack of knowledge on the toxicity of thiamethoxam to crustaceans motivates our research to study the acute and chronic toxicity of decapod crustaceans Litopenaeus vannamei, exposed to thiamethoxam. A 28-day chronic toxicity test followed a 96 h acute toxicity test. Thiamethoxam induced oxidative stress and decreased growth performance in shrimp. In addition, thiamethoxam has led to a substantial imbalance of the micro-ecosystem in the intestine. The composition of the intestinal flora changed significantly, and the balance of the interaction network in genera was broken. The competitive interaction of many bacteria becomes an unstable cooperative interaction. Transcriptomic analysis showed that the numbers of up- and down-regulated differentially expressed genes (DEGs) increased in a dose-dependent manner. These DEGs were significantly enriched in pathways related to detoxification, and the expression of most detoxification genes was upregulated. DEGs related to detoxification were positively correlated with Shimia and negatively correlated with Pseudoalteromonas. This study provides evidence for the first time on the toxic effects of thiamethoxam on the growth, biochemistry, intestinal flora, and transcriptome in crustaceans.

Distinct bacterial communities in the environmental water, sediment and intestine between two crayfish-plant coculture ecosystems

Microorganisms are an important part of productivity, water quality, and biogeochemical cycles in an aquaculture ecosystems and play a key role in determining the growth and fitness of aquaculture animals. Coculture ecosystems are widely applied with great significance in agricultural production worldwide. The crayfish-rice coculture ecosystem (CRCE) and crayfish-waterweed coculture ecosystem (CWCE) are two high-profile artificial ecosystems for crayfish culture. However, the bacterial communities of the environmental water, sediment, and intestine in the CRCE and CWCE remain elusive. In this study, we investigated the diversity, composition, and function of bacterial communities in water, sediment, and intestine samples from the CRCE to CWCE. The physicochemical factors of water [such as ORP (oxidation-reduction potential), TC (total carbon), TOC (total oxygen carbon), and NO₃^--N] and sediment [such as TC, TOC, TN (total nitrogen), and TP (total phosphate)] were significantly different in the CRCE and CWCE. The abundances of Proteobacteria, Actinobacteria, Verrucomicrobia, Cyanobacteria, Chlorobi, Chloroflexi, and Firmicutes were significantly different in the water bacterial communities of the CRCE and CWCE. The abundance of Vibrio in the crayfish intestine was higher in the CRCE than in the CWCE. The most abundant phyla in the CRCE and CWCE sediment were Proteobacteria and Bacteroidetes. The abundances of genes involved in transporters and ABC transporters were different in water of CRCE and CWCE. The abundances of genes involved in oxidative phosphorylation were significantly higher in the crayfish intestine of the CRCE than in that of the CWCE. Furthermore, the functional genes associated with carbon metabolism were significantly more abundant in the sediment of the CRCE than in that of the CWCE. Spearman correlation analysis and redundancy analysis (RDA) showed that the bacterial communities of the water and sediment in the CRCE and CWCE were correlated with environmental factors (pH, total carbon (TC), total oxygen carbon (TOC), total nitrogen (TN), and total phosphorus (TP)). Our findings showed that the composition, diversity and function of the bacterial communities were distinct in the environmental water, sediment, and intestine of the CRCE and CWCE crayfish coculture ecosystems due to their different ecological patterns. These results can help guide healthy farming practices and deepen the understanding of bacterial communities in crayfish-plant coculture ecosystems from the perspective of bacterial ecology. KEY POINTS: • The composition of bacterial communities in the environmental water, sediment, and intestine of the CRCE and CWCE were distinct. ̉• The abundances of genes involved in transporters and ABC transporters were different in the water of the CRCE and CWCE. • The bacterial communities of the water and sediment in the CRCE and CWCE were correlated with some environmental factors.

Comparable Ecological Processes Govern the Temporal Succession of Gut Bacteria and Microeukaryotes as Shrimp Aged

Understanding the rules that govern the successions of gut microbiota is prerequisite for testing general ecological theories and sustaining a desirable microbiota. However, the ignorance of microeukaryotes raises the question of whether gut microeukaryotes are assembled according to the same rules as bacteria. We tracked the shrimp gut bacterial and microeukaryotic communities by a longitudinal dense sampling. The successions of both domains were significantly correlated with host age, with relatively stable microeukaryotic communities in adult shrimp. Gut microeukaryotes exhibited significantly higher turnover rate, but fewer transient species, lower proportion of temporal generalists, and narrower habitat niche breadth than bacteria. The γ-diversity partitioning analysis revealed that the successions of gut microbiotas were primarily ascribed to the high dissimilarity as shrimp aged ([Formula: see text]_IntraTimes), whereas the relative importance of [Formula: see text]_IntraTimes was significantly higher for microeukaryotes than that for bacteria. Compared with contrasting ecological processes in governing free-living bacteria and microeukaryotes, the ecological patterns were comparable between host-associated gut counterparts. However, the gut microeukaryotes were governed more strongly by deterministic selection relative to nestedness compared with the gut bacteria, which supports the "size-plasticity" hypothesis. Our results highlight the importance of independently interpreting free-living and host-associated meta-communities for a comprehensive understanding of the processes that govern microbial successions.

Dissimilarity of microbial diversity of pond water, shrimp intestine and sediment in Aquamimicry system

The Pacific white shrimp, with the largest production in shrimp industry, has suffered from multiple severe viral and bacterial diseases, which calls for a more reliable and environmentally friendly system to promote shrimp culture. The "Aquamimicry system", mimicking the nature of aquatic ecosystems for the well-being of aquatic animals, has effectively increased shrimp production and been adapted in many countries. However, the microbial communities in the shrimp intestine and surrounding environment that act as an essential component in Aquamimicry remain largely unknown. In this study, the microbial composition and diversity alteration in shrimp intestine, surrounding water and sediment at different culture stages were investigated by high throughput sequencing of 16S rRNA gene, obtaining 13,562 operational taxonomic units (OTUs). Results showed that the microbial communities in shrimp intestine and surrounding environment were significantly distinct from each other, and 23 distinguished taxa for each habitat were further characterized. The microbial communities differed significantly at different culture stages, confirmed by a great number of OTUs dramatically altered during the culture period. A small part of these altered OTUs were shared between shrimp intestine and surrounding environment, suggesting that the microbial alteration of intestine was not consistent with that of water and sediment. Regarding the high production of Aquamimicry farm used as a case in this study, the dissimilarity between intestinal and surrounding microbiota might be considered as a potential indicator for healthy status of shrimp farming, which provided hints on the appropriate culture practices to improve shrimp production.

Fine-scale succession patterns and assembly mechanisms of bacterial community of Litopenaeus vannamei larvae across the developmental cycle

BACKGROUND

Microbiome assembly in early life may have a long-term impact on host health. Larval nursery is a crucial period that determines the success in culture of Litopenaeus vannamei, the most productive shrimp species in world aquaculture industry. However, the succession patterns and assembly mechanisms of larval shrimp bacterial community still lack characterization at a fine temporal scale. Here, using a high-frequency sampling strategy and 16S rRNA gene amplicon sequencing, we investigated dynamics of larval shrimp bacterial community and its relationship with bacterioplankton in the rearing water across the whole developmental cycle in a realistic aquaculture practice.

RESULTS

Alpha-diversity of larval shrimp bacteria showed a U-shaped pattern across the developmental cycle with the stages zoea and mysis as the valley. Correspondingly, the compositions of dominant bacterial taxa at the stages nauplius and early postlarvae were more complex than other stages. Remarkably, Rhodobacteraceae maintained the overwhelming dominance after the mouth opening of larvae (zoea I~early postlarvae). The taxonomic and phylogenetic compositions of larval bacterial community both showed stage-dependent patterns with higher rate of taxonomic turnover, suggesting that taxonomic turnover was mainly driven by temporal switching among closely related taxa (such as Rhodobacteraceae taxa). The assembly of larval bacteria was overall governed by neutral processes (dispersal among individuals and ecological drift) at all the stages, but bacterioplankton also had certain contribution during three sub-stages of zoea, when larval and water bacterial communities were most associated. Furthermore, the positive host selection for Rhodobacteraceae taxa from the rearing water during the zoea stage and its persistent dominance and large predicted contribution to metabolic potentials of organic matters at post-mouth opening stages suggest a crucial role of this family in larval microbiome and thus a potential source of probiotic candidates for shrimp larval nursery.

CONCLUSIONS

Our results reveal pronounced succession patterns and dynamic assembly processes of larval shrimp bacterial communities during the developmental cycle, highlighting the importance of the mouth opening stage from the perspective of microbial ecology. We also suggest the possibility and potential timing in microbial management of the rearing water for achieving the beneficial larval microbiota in the nursery practice. Video Abstract.

Understanding the role of the shrimp gut microbiome in health and disease

With rapid increases in the global shrimp aquaculture sector, a focus on animal health during production becomes ever more important. Animal productivity is intimately linked to health, and the gut microbiome is becoming increasingly recognised as an important driver of cultivation success. The microbes that colonise the gut, commonly referred to as the gut microbiota or the gut microbiome, interact with their host and contribute to a number of key host processes, including digestion and immunity. Gut microbiome manipulation therefore represents an attractive proposition for aquaculture and has been suggested as a possible alternative to the use of broad-spectrum antibiotics in the management of disease, which is a major limitation of growth in this sector. Microbiota supplementation has also demonstrated positive effects on growth and survival of several different commercial species, including shrimp. Development of appropriate gut supplements, however, requires prior knowledge of the host microbiome. Little is known about the gut microbiota of the aquatic invertebrates, but penaeid shrimp are perhaps more studied than most. Here, we review current knowledge of information reported on the shrimp gut microbiota, highlighting the most frequently observed taxa and emphasizing the dominance of Proteobacteria within this community. We discuss involvement of the microbiome in the regulation of shrimp health and disease and describe how the gut microbiota changes with the introduction of several economically important shrimp pathogens. Finally, we explore evidence of microbiome supplementation and consider its role in the future of penaeid shrimp production.

Microecological Koch's postulates reveal that intestinal microbiota dysbiosis contributes to shrimp white feces syndrome

BACKGROUND

Recently, increasing evidence supports that some complex diseases are not attributed to a given pathogen, but dysbiosis in the host intestinal microbiota (IM). The full intestinal ecosystem alterations, rather than a single pathogen, are associated with white feces syndrome (WFS), a globally severe non-infectious shrimp disease, while no experimental evidence to explore the causality. Herein, we conducted comprehensive metagenomic and metabolomic analysis, and intestinal microbiota transplantation (IMT) to investigate the causal relationship between IM dysbiosis and WFS.

RESULTS

Compared to the Control shrimp, we found dramatically decreased microbial richness and diversity in WFS shrimp. Ten genera, such as Vibrio, Candidatus Bacilloplasma, Photobacterium, and Aeromonas, were overrepresented in WFS, whereas 11 genera, including Shewanella, Chitinibacter, and Rhodobacter were enriched in control. The divergent changes in these populations might contribute the observation that a decline of pathways conferring lipoic acid metabolism and mineral absorption in WFS. Meanwhile, some sorts of metabolites, especially lipids and organic acids, were found to be related to the IM alteration in WFS. Integrated with multiomics and IMT, we demonstrated that significant alterations in the community composition, functional potentials, and metabolites of IM were closely linked to shrimp WFS. The distinguished metabolites which were attributed to the IM dysbiosis were validated by feed-supplementary challenge. Both homogenous selection and heterogeneous selection process were less pronounced in WFS microbial community assembly. Notably, IMT shrimp from WFS donors eventually developed WFS clinical signs, while the dysbiotic IM can be recharacterized in recipient shrimp.

CONCLUSIONS

Collectively, our findings offer solid evidence of the causality between IM dysbiosis and shrimp WFS, which exemplify the 'microecological Koch's postulates' (an intestinal microbiota dysbiosis, a disease) in disease etiology, and inspire our cogitation on etiology from an ecological perspective. Video abstract.

Identification of Multigene Biomarker for Shrimp White Feces Syndrome by Full-Length Transcriptome Sequencing

The pacific white shrimp, Litopenaeus vannamei, with the largest shrimp industry production in the world, is currently threatened by a severe disease, white feces syndrome (WFS), which cause devastating losses globally, while its causal agents remain largely unknown. Herein, compared to the Control shrimp by metagenomic analysis, we firstly investigated that the altered functions of intestinal microbial community in WFS shrimp were the enrichment of bacterial chemotaxis and flagellar assembly pathways, hinting at a potential role of pathogenic bacteria for growth and development, which might be related to WFS occurrence. Single-molecule real-time (SMRT) sequencing was to further identify the gene structure and gene regulation for more clues in WFS aetiology. Totally 50,049 high quality transcripts were obtained, capturing 39,995 previously mapped and 10,054 newly detected transcripts, which were annotated to 30,554 genes. A total of 158 differentially expressed genes (DEGs) were characterized in WFS shrimp. These DEGs were strongly associated with various immune related genes that regulated the expression of multiple antimicrobial peptides (e.g., antilipopolysaccharide factors, penaeidins, and crustin), which were further experimentally validated using quantitative PCR on transcript level. Collectively, multigene biomarkers were identified to be closely associated with WFS, especially those functional alterations in microbial community and the upregulated immune related gene with antibacterial activities. Our finding not only inspired our cogitation on WFS aetiology from both microbial and host immune response perspectives with combined metagenomic and full-length transcriptome sequencing, but also provided valuable information for enhancing shrimp aquaculture.

Spatiotemporal successions of shrimp gut microbial colonization: high consistency despite distinct species pool

Aquatic animals encounter suites of novel planktonic microbes during their development. Although hosts have been shown to exert strong selection on their gut microbiota from surrounding environment, to what extent and the generality that the gut microbiota and the underlying ecological processes are affected by biotic and abiotic variations are largely unclear. Here, these concerns were explored by coupling spatiotemporal data on gut and rearing water bacterial communities with environmental variables over shrimp life stages at spatially distant locations. Shrimp gut microbiotas significantly changed mirroring their development, as evidenced by gut bacterial signatures of shrimp life stage contributing 95.5% stratification accuracy. Shrimp sourced little (2.6%-15.8%) of their gut microbiota from their rearing water. This microbial resistance was reflected by weak compositional differences between shrimp farming spatially distinct locations where species pools were distinct. Consistently, the assembly of shrimp gut microbiota was not adequately explained by the rearing water variables and bacterial community, but rather by host-age-associated biotic features. The successions of shrimp gut microbiota were droved by replacement (βsim), rather than by nestedness (βnes), while those of bacterioplankton communities were equally governed by replacement and nestedness. Our study highlights how shrimp gut bacterial community assembly is coupled to their development, rearing species pool, and that the successional pattern of host-associated communities is differed from that of free-living bacteria.

Pinning down the role of common luminal intestinal parasitic protists in human health and disease - status and challenges

While some single-celled intestinal parasites are direct causes of diarrhoea and other types of intestinal pathology, the impact of other gut micro-eukaryotes on human health remains elusive. The fact that some common luminal intestinal parasitic protists (CLIPPs) have lately been found more often in healthy than in diseased individuals has fuelled the hypothesis that some parasites might in fact be protective against disease. To this end, the use of new DNA technologies has helped us investigate trans-kingdom relationships in the gut. However, research into these relationships is currently hampered by the limited data available on the genetic diversity within the CLIPPs genera, which results in limited efficacy of publicly available DNA sequence databases for taxonomic annotation of sequences belonging to the eukaryotic component of the gut microbiota. In this paper, I give a brief overview of the status on CLIPPs in human health and disease and challenges related to the mapping of intestinal eukaryotic diversity of the human gut.

Starvation stress affects the interplay among shrimp gut microbiota, digestion and immune activities

Aquatic animals are frequently suffered from starvation due to restricted food availability or deprivation. It is currently known that gut microbiota assists host in nutrient acquisition. Thus, exploring the gut microbiota responses would improve our understanding on physiological adaptation to starvation. To achieve this, we investigated how the gut microbiota and shrimp digestion and immune activities were affected under starvation stress. The results showed that the measured digestion activities in starved shrimp were significantly lower than in normal cohorts; while the measured immune activities exhibited an opposite trend. A structural equation modeling (SEM) revealed that changes in the gut bacterial community were directly related to digestive and immune enzyme activities, which in turn markedly affected shrimp growth traits. Notably, several gut bacterial indicators that characterized the shrimp nutrient status were identified, with more abundant opportunistic pathogens in starved shrimp, although there were no statistical differences in the overall diversity and the structures of gut bacterial communities between starved and normal shrimp. Starved shrimp exhibited less connected and cooperative interspecies interaction as compared with normal cohorts. Additionally, the functional pathways involved in carbohydrate and protein digestion, glycan biosynthesis, lipid and enzyme metabolism remarkably decreased in starved shrimp. These attenuations could increase the susceptibility of starved shrimp to pathogens infection. In summary, this study provides novel insights into the interplay among shrimp digestion, immune activities and gut microbiota in response to starvation stress.

Quantitative PCR Analysis of Gut Disease-Discriminatory Phyla for Determining Shrimp Disease Incidence

There is evidence that gut microbial signatures are indicative of host health status. However, few efforts have been devoted to establishing an applicable technique for determining disease incidence by using gut microbial signatures. Herein, we established a quantitative PCR (qPCR)-based approach to detect the relative abundances of gut disease-discriminatory phyla, which in turn afforded independent variables for quantitatively determining the incidence of shrimp disease. Given the temporal dynamics of gut bacterial communities as healthy shrimp aged, we identified disease-discriminatory phyla after ruling out age-discriminatory phyla. The top 10 disease-discriminatory phyla contributed to an overall 93.2% accuracy in diagnosis (n = 103 samples from shrimp that were determined with high confidence to be healthy or that exhibited apparent disease symptoms and subsequent death), with 70% diagnosis accuracy at the disease onset stage, when symptoms or signs of disease were not apparent. 16S rRNA gene-targeted group-specific primers of five disease-discriminatory phyla were then designed according to their compositions within shrimp gut microbiota, and other primers were borrowed from previous studies. The relative abundances of the 10 disease-discriminatory phyla assayed by qPCR exhibited a high consistency (r = 0.946, P < 0.001) with those detected by Illumina sequencing. Notably, using the profiles of disease-discriminatory phyla assayed by qPCR and the corresponding weight coefficients as independent variables, we were able to accurately estimate the incidences of future disease outcome. This work establishes an applicable technique to quantitatively determine the incidence and onset of shrimp disease, which is a valuable attempt to translate scientific research into a practical application.IMPORTANCE Current studies have identified gut microbial signatures of host health using high-throughput sequencing (HTS) techniques. However, HTS is still expensive and time-consuming and requires a high technical ability, thereby impeding its application in routine monitoring in aquaculture. Hence, it is necessary to seek an alternative strategy to overcome these shortcomings. Herein, we establish a qPCR-based approach to detect the relative abundances of gut disease-discriminatory phyla, which in turn afford independent variables to quantitatively determine the incidence and onset of shrimp disease. Notably, there is a high consistency between the accuracies of disease diagnosis achieved by qPCR and HTS. This applicable technique makes important progress toward defining a diseased state in shrimp and toward solving an important animal health management-driven economic problem.

Response of host-bacterial colonization in shrimp to developmental stage, environment and disease

The host-associated microbiota is increasingly recognized to facilitate host fitness, but the understanding of the underlying ecological processes that govern the host-bacterial colonization over development and, particularly, under disease remains scarce. Here, we tracked the gut microbiota of shrimp over developmental stages and in response to disease. The stage-specific gut microbiotas contributed parallel changes to the predicted functions, while shrimp disease decoupled this intimate association. After ruling out the age-discriminatory taxa, we identified key features indicative of shrimp health status. Structural equation modelling revealed that variations in rearing water led to significant changes in bacterioplankton communities, which subsequently affected the shrimp gut microbiota. However, shrimp gut microbiotas are not directly mirrored by the changes in rearing bacterioplankton communities. A neutral model analysis showed that the stochastic processes that govern gut microbiota tended to become more important as healthy shrimp aged, with 37.5% stochasticity in larvae linearly increasing to 60.4% in adults. However, this defined trend was skewed when disease occurred. This departure was attributed to the uncontrolled growth of two candidate pathogens (over-represented taxa). The co-occurrence patterns provided novel clues on how the gut commensals interact with candidate pathogens in sustaining shrimp health. Collectively, these findings offer updated insight into the ecological processes that govern the host-bacterial colonization in shrimp and provide a pathological understanding of polymicrobial infections.

Progress in the gut microbiota in exploring shrimp disease pathogenesis and incidence

It is now recognized that gut microbiota contributes indispensable roles in safeguarding host health. Shrimp is being threatened by newly emerging diseases globally; thus, understanding the driving factors that govern its gut microbiota would facilitate an initial step to reestablish and maintain a "healthy" gut microbiota. This review summarizes the factors that assemble the shrimp gut microbiota, which focuses on the current progresses of knowledge linking the gut microbiota and shrimp health status. In particular, I propose the exploration of shrimp disease pathogenesis and incidence based on the interplay between dysbiosis in the gut microbiota and disease severity. An updated research on shrimp disease toward an ecological perspective is discussed, including host-bacterial colonization, identification of polymicrobial pathogens and diagnosing disease incidence. Further, a simple conceptual model is offered to summarize the interplay among the gut microbiota, external factors, and shrimp disease. Finally, based on the review, current limitations are raised and future studies directed at solving these concerns are proposed. This review is timely given the increased interest in the role of gut microbiota in disease pathogenesis and the advent of novel diagnosis strategies.