As the human population continues to grow, food production industries such as aquaculture will need to expand as well. In order to preserve the environment and the natural resources, this expansion ...will need to take place in a sustainable way. Biofloc technology is a technique of enhancing water quality in aquaculture through balancing carbon and nitrogen in the system. The technology has recently gained attention as a sustainable method to control water quality, with the added value of producing proteinaceous feed in situ. In this review, we will discuss the beneficial effects of the technology and identify some challenges for future research.
► Biofloc technology aims at enhancing water quality through balancing C and N. ► Heterotrophic bacteria assimilate inorganic N waste into biomass. ► The bioflocs can be used as proteinaceous feed for the cultured animals. ► We discuss advantages of biofloc technology and challenges for further research.
β-Glucans are a heterogeneous group of glucose polymers with a common structure comprising a main chain of β-(1,3) and/or β-(1,4)-glucopyranosyl units, along with side chains with various branches ...and lengths. β-Glucans initiate immune responses via immune cells, which become activated by the binding of the polymer to specific receptors. However, β-glucans from different sources also differ in their structure, conformation, physical properties, binding affinity to receptors, and thus biological functions. The mechanisms behind this are not fully understood. This mini-review provides a comprehensive and up-to-date commentary on the relationship between β-glucans' structure and function in relation to their use for immunomodulation.
Shrimp, as a high-protein animal food commodity, are one of the fastest growing food producing sectors in the world. It has emerged as a highly traded seafood product, currently exceeding 8 MT of ...high value. However, disease outbreaks, which are considered as the primary cause of production loss in shrimp farming, have moved to the forefront in recent years and brought socio-economic and environmental unsustainability to the shrimp aquaculture industry. Acute hepatopancreatic necrosis disease (AHPND), caused by
spp., is a relatively new farmed penaeid shrimp bacterial disease. The shrimp production in AHPND affected regions has dropped to ~60%, and the disease has caused a global loss of USD 43 billion to the shrimp farming industry. The conventional approaches, such as antibiotics and disinfectants, often applied for the mitigation or cure of AHPND, have had limited success. Additionally, their usage has been associated with alteration of host gut microbiota and immunity and development of antibiotic resistance in bacterial pathogens. For example, the Mexico AHPND-causing
strain (13-306D/4 and 13-511/A1) were reported to carry tetB gene coding for tetracycline resistance gene, and
from China was found to carry multiple antibiotic resistance genes. As a consequence, there is an urgent need to thoroughly understand the virulence mechanism of AHPND-causing
spp. and develop novel management strategies to control AHPND in shrimp aquaculture, that will be crucially important to ensure food security in the future and offer economic stability to farmers. In this review, the most important findings of AHPND are highlighted, discussed and put in perspective, and some directions for future research are presented.
Probiotics have emerged as promising alternatives for improving resistance to diseases and stimulating growth of farmed shrimp. The aim of the present work was to assess the effect of probiotic ...addition on shrimp survival and growth performance through meta-analysis. PubMed, SciELO and Google Scholar search engines were searched for relevant studies published from 1980 to 2017 without language exclusion. We only selected the experiments from articles using penaeid shrimps without apparent disease, with the results published in peer-reviewed journals with any dispersion measure. Survival, specific growth rate (SGR) and feed conversion ratio (FCR) were selected as outcomes. We evaluated experimental design, penaeid shrimp species, larval or postlarval stage, probiotic strain, modes of administration among others. A total of 100, 60 and 49 experiments were included to assess probiotic effects on survival, SGR and FCR, respectively. Probiotics increased survival compared to controls (SMD = 3.068, 95% CI 2.594 to 3.543) and improved SGR (SMD = 3.811, 95% CI 3.269 to 4.354) and FCR (SMD = −3.194, 95% CI -3.469 to −2.920) in the pooled standardized mean difference random effect model, considering the source of heterogeneity and publication biases (i.e. where the decision to publish or not depends on the outcome of the experiment, e.g. withhold negative outcomes). Survival, SGR and FCR were improved in shrimps treated with probiotic. To our knowledge, this is the first report of a meta-analysis designed to investigate the effects of probiotics on shrimp survival and growth performance.
•Meta-analysis was performed to assess probiotics effects on the growth performance of shrimp.•Probiotic supplementation increased specific growth rate and improve feed conversion ratio.•Probiotics research/field trials in shrimp should consider to include the microorganism in the feed.•Multi-strains probiotics can improve their effect in shrimp better than mono-strain.
...the identification of novel drug targets and the development of novel therapeutics constitute an important area of current scientific research. ...the major virulence factors responsible for ...infection of the host could be targeted directly instead of blocking their expression by QS disruption (for reviews on this strategy, see 61, 62).
The invertebrate's innate immune system was reported to show some form of adaptive features, termed trained immunity. However, the memory characteristics of innate immune system and the mechanisms ...behind such phenomena remain unclear. Using the invertebrate model Artemia, we verified the possibility or impossibility of trained immunity, examining the presence or absence of enduring memory against homologous and heterologous antigens (Vibrio spp.) during a transgenerational study. We also determined the mechanisms behind such phenomenon. Our results showed the occurrence of memory and partial discrimination in Artemia's immune system, as manifested by increased resistance, for three successive generations, of the progenies of Vibrio-exposed ancestors towards a homologous bacterial strain, rather than to a heterologous strain. This increased resistance phenotype was associated with elevated levels of hsp70 and hmgb1 signaling molecules and alteration in the expression of key innate immunity-related genes. Our results also showed stochastic pattern in the acetylation and methylation levels of H4 and H3K4me3 histones, respectively, in the progenies whose ancestors were challenged. Overall results suggest that innate immune responses in invertebrates have the capacity to be trained, and epigenetic reprogramming of (selected) innate immune effectors is likely to have central place in the mechanisms leading to trained immunity.
Acute Hepatopancreatic Necrosis Disease (AHPND) causes significant mortality in shrimp aquaculture. The infection is primarily instigated by Vibrio parahaemolyticus (Vp) strains carrying a plasmid ...encoding the binary toxin PirAB. Yet, comprehension of supplementary virulence factors associated with this relatively recent disease remains limited. Furthermore, the same holds for gastroenteritis in humans caused by other Vp genotypes. Additionally, given the prevalent use of antibiotics to combat bacterial infections, it becomes imperative to illuminate the presence of antimicrobial resistance genes within these bacteria.
A subsampled number of 1,036 Vp genomes was screened for the presence of antimicrobial resistance genes, revealing an average prevalence of 5 ± 2 (SD) genes. Additional phenotypic antimicrobial susceptibility testing of three Vp strains (M0904, TW01, and PV1) sequenced in this study demonstrated resistance to ampicillin by all tested strains. Additionally, Vp M0904 showed multidrug resistance (against ampicillin, tetracycline, and trimethoprim-sulfamethoxazole). With a focus on AHPND, a screening of all Vibrio spp. for the presence of pirA and/or pirB indicates an estimated prevalence of 0.6%, including four V. campbellii, four V. owensii, and a Vibrio sp. next to Vp. Their pirAB-encoding plasmids exhibited a highly conserved backbone, with variations primarily in the region of the Tn3 family transposase. Furthermore, an assessment of the subsampled Vp genomes for the presence of known virulence factors showed a correlation between the presence of the Type 3 Secretion System 2 and tdh, while the presence of the Type 6 Secretion System 1 was clade dependent. Furthermore, a genome-wide association study (GWAS) unveiled (new) genes associated with pirA, pirB, tdh, and trh genotypes. Notable associations with the pirAB genotype included outer membrane proteins, immunoglobulin-like domain containing proteins, and toxin-antitoxin systems. For the tdh + /trh + genotypes (containing tdh, trh, or both genes), associations were found with T3SS2 genes, urease-related genes and nickel-transport system genes, and genes involved in a 'minimal' type I-F CRISPR mechanism.
This study highlights the prevalence of antimicrobial resistance and virulence genes in Vp, identifying novel genetic markers associated with AHPND and tdh + /trh + genotypes. These findings contribute valuable insights into the genomic basis of these genotypes, with implications for shrimp aquaculture and food safety.
The biofloc system is a relatively new aquaculture technology that offers practical solution to maintain culture water quality by recycling nutrients and improves the health status and resistance of ...shrimps against microbial infection, yet the mode of action involved remains unclear. This study aimed to unravel the underlying mechanism behind the protective effect of a biofloc system using
Litopenaeus vannamei
and acute hepatopancreatic necrosis disease (AHPND)-causing
Vibrio parahaemolyticus
M0904 strain as a host-pathogen model. The results showed that a biofloc system maintained at a C/N ratio of 15, improves the water quality and contributes to the nutrition of cultured animals as bioflocs might serve as an additional protein source. Furthermore, the study demonstrated that the biofloc system enhances the survival of
L. vannamei
upon challenge with a
V. parahaemolyticus
AHPND strain. Remarkably, the results highlight that in the biofloc system, AHPND-causing
V. parahaemolyticus
possibly switch from free-living virulent planktonic phenotype to a non-virulent biofilm phenotype, as demonstrated by a decreased transcription of flagella-related motility genes (
flaA
,
CheR
, and
fliS
), Pir toxin (
PirB
VP
), and AHPND plasmid genes (
ORF14
) and increased expression of the phenotype switching marker
AlkPhoX
gene in both
in vitro
and
in vivo
conditions. Taken together, results suggest that biofloc steer phenotype switching, contributing to the decreased virulence of
V. parahaemolyticus
AHPND strain toward shrimp postlarvae. This information reinforces our understanding about AHPND in a biofloc setting and opens the possibility to combat AHPND not only by trying to eliminate the AHPND-causing
V. parahaemolyticus
from the system but rather to steer the phenotypic switch.
Emerging, infectious diseases in shrimp like acute hepatopancreatic necrosis disease (AHPND) caused by
and mortality caused by other
species such as
are worldwide related to huge economic losses in ...industrial shrimp production. As a strategy to prevent disease outbreaks, a plant-based phenolic compound could be used as a biocontrol agent. Here, using the brine shrimp (
) as a model system, we showed that phloroglucinol treatment of the parental animals at early life stages resulted in transgenerational inherited increased resistance in their progeny against biotic stress, i.e., bacteria (
AHPND strain and
) and abiotic stress, i.e., lethal heat shock. Increased resistance was recorded in three subsequent generations. Innate immune-related gene expression profiles and potential epigenetic mechanisms were studied to discover the underlying protective mechanisms. Our results showed that phloroglucinol treatment of the brine shrimp parents significantly (
< 0.05) enhanced the expression of a core set of innate immune genes (
, and
) in subsequent generations. We also demonstrated that epigenetic mechanisms such as DNA methylation, m6A RNA methylation, and histone acetylation and methylation (active chromatin marker i.e., H3K4Me3, H3K4me1, H3K27me1, H3 hyperacetylation, H3K14ac and repression marker, i.e., H3K27me3, H4 hypoacetylation) might play a role in regulation of gene expression leading toward the observed transgenerational inheritance of the resistant brine shrimp progenies. To our knowledge, this is the first report on transgenerational inheritance of a compound-induced robust protected phenotype in brine shrimp, particularly protected against AHPND caused by
and vibriosis caused by
. Results showed that epigenetic reprogramming is likely to play a role in the underlying mechanism.
The symbiotic gut microbial community is generally known to have a strong impact on the fitness of its host. Nevertheless, it is less clear how the impact of symbiotic interactions on the hosts' ...fitness varies according to environmental circumstances such as changes in the diet. This study aims to get a better understanding of host-microbiota interactions under different levels of food availability. We conducted experiments with the invertebrate, experimental model organism Daphnia magna and compared growth, survival and reproduction of conventionalized symbiotic Daphnia with germ-free individuals given varying quantities of food. Our experiments revealed that the relative importance of the microbiota for the hosts' fitness varied according to dietary conditions. The presence of the microbiota had strong positive effects on Daphnia when food was sufficient or abundant, but had weaker effects under food limitation. Our results indicate that the microbiota can be a potentially important factor in determining host responses to changes in dietary conditions. Characterization of the host-associated microbiota further showed that Aeromonas sp. was the most prevalent taxon in the digestive tract of Daphnia.
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