Effects of Bacillus aryabhattai TBRC8450 on vibriosis resistance and immune enhancement in Pacific white shrimp, Litopenaeus vannamei

A Review on Biofloc System Technology, History, Types, and Future Economical Perceptions in Aquaculture

Given the scarcity of water and land resources, coupled with the competitive nature of aquaculture, the long-term viability of this industry will depend on strategies for vertical development. This involves enhancing production environments, increasing productivity, and advancing aquaculture technologies. The use of biofloc technology offers a potential solution to mitigate the adverse environmental impacts and the heavy reliance on fishmeal in the aquaculture sector. This method is designed to effectively assimilate inorganic nitrogen found in aquaculture wastewater, thereby enhancing water quality. Additionally, this process produces microbial protein, which can serve as a viable supplemental feed for aquatic animals. Furthermore, this technique has the potential to reduce the feed conversion ratio, thereby lowering overall production costs. This article provides an overview of the evolving field of biofloc system technology within aquaculture. In this study, we will examine the historical development and various types of biofloc systems, as well as the factors that influence their effectiveness. Finally, we will explore the economic potential of implementing biofloc systems in aquaculture.

Lactic Acid Bacteria of Marine Origin as a Tool for Successful Shellfish Farming and Adaptation to Climate Change Conditions

Climate change, especially in the form of temperature increase and sea acidification, poses a serious challenge to the sustainability of aquaculture and shellfish farming. In this context, lactic acid bacteria (LAB) of marine origin have attracted attention due to their ability to improve water quality, stimulate the growth and immunity of organisms, and reduce the impact of stress caused by environmental changes. Through a review of relevant research, this paper summarizes previous knowledge on this group of bacteria, their application as protective probiotic cultures in mollusks, and also highlights their potential in reducing the negative impacts of climate change during shellfish farming. Furthermore, opportunities for further research and implementation of LAB as a sustainable and effective solution for adapting mariculture to changing climate conditions were identified.

Beneficial effects of indigenous Bacillus spp. on growth, antioxidants, immunity and disease resistance of Rhynchocypris lagowskii

This study aimed to investigate the effect of Bacillus aryabhattai (LSG3-7) and Bacillus mojavensis (LSG3-8) on growth performance, antioxidant capacity, and immune response in Rhynchocypris lagowskii (Dybowski, 1869), at the trial and challenge periods. A 630 healthy fish (10.76 ± 0.05) were randomly divided into six groups: control group (D1) was fed the basal diet, D2 and D3 were supplemented with LSG 3-7 and LSG3-8 (1 × 108 CFU/g) for both of them, whereas D4 was supplemented with a mixture of both bacteria (0.5 × 108 CFU/g each), and D5 was supplemented with LSG3-7 0.75 × 108 CFU/g + LSG3-8 0.25 × 108 CFU/g, and D6 supplemented with LSG3-7 0.25 × 108 CFU/g + LSG3-8 0.75 × 108 CFU/g. After the trial, Aeromonas hydrophila was used in a challenge test for 14 days. Treatments showed significant differences (p < 0.05) in growth performance and antioxidant capacity (CAT, CuZn-SOD, GPX) in the liver and intestine compared to the control. The antioxidant-related genes CAT, CuZn-SOD, GPX, and Nrf2 in the liver and intestine showed upregulation compared with the control group. Serum IgM, LZM, C3, C4, and AKP showed a favorable superiority (p < 0.05) in treatments (D2 - D6) at the trial and challenge test compared to controls. In parallel, immune-related genes (IgM, NF-κB, TLR-1, TLR-2, and MyD88) showed an up-regulated level (p < 0.05) in treatments (D2 - D6) compared to the control. In addition, pro-inflammatory cytokines (IL-1, TNF-α) showed a downregulated level in treatments (D2 - D6). After the challenge test, the immune-related genes in the liver and muscle showed an up-regulated level in treatments compared to the controls. The survival rate showed a significant increase (p < 0.05) in the treatment groups (D2 - D6) compared to the control. Overall, individuals and the bacterial mixture of B. aryabhattai and B. mojavensis could improve the growth performance, antioxidant capacity, immune capacity, and survival rate of R. lagowskii and prevent side effects of A. hydrophila. However, B. mojavensis showed a slight improvement compared to B. aryabhattai without a significant difference between them.

Detoxification of aflatoxin B1 by Bacillus aryabhattai through conversion of double bond in terminal furan

AIMS

This study aimed to screen a bacterial strain with high detoxifying capability for aflatoxin B1 (AFB1), verify its biotransformation efficiency, and detoxification process.

METHODS AND RESULTS

A total of 350 samples collected from different environmental niche were screened using coumarin as the sole carbon source. High Performance Liquid Chromatography (HPLC) was used to detect residues of AFB1, and 16S rRNA sequencing was performed on the isolated strain with the highest AFB1 removal ratio for identification. The detoxified products of this strain were tested for toxicity in Escherichia coli as well as LO2, Caco-2, and HaCaT human cell lines. HPLC-MS was applied to further confirm the AFB1 removal and detoxification process.

CONCLUSIONS

We identified a strain from plant leaf designated as DT with high AFB1-detoxifying ability that is highly homologous to Bacillus aryabhattai. The optimum detoxification conditions of this strain were 37°C and pH 8.0, resulting in 82.92% removal ratio of 2 μg mL-1 AFB1 in 72 h. The detoxified products were nontoxic for E. coli and significantly less toxic for the LO2, Caco-2, and HaCaT human cell lines. HPLC-MS analysis also confirmed the significant drop of the AFB1 characteristic peak. Two possible metabolic products, C19H15O8 (m/z 371) and C19H19O8 (m/z 375), were observed by mass spectrometry. Potential biotransformation pathway was based on the cleavage of double bond in the terminal furan of AFB1. These generated components had different chemical structures with AFB1, manifesting that the attenuation of AFB1 toxicity would be attributed to the destruction of lactone structure of AFB1 during the conversion process.

Identification and evaluation of potential probiotics against skin-ulceration disease in the Chinese tongue sole (Cynoglossus semilaevis)

In this study, three highly pathogenic bacterial strains (Vibrio harveyi TB6, Vibrio alginolyticus TN1, and Vibrio parahaemolyticus TN3) were isolated from skin ulcers and intestines of diseased Chinese tongue sole (Cynoglossus semilaevis). The bacteria were investigated using hemolytic activity tests, in vitro co-culture with intestinal epithelial cells, and artificial infection of C. semilaevis. A further 126 strains were isolated from the intestines of healthy C. semilaevis. The three pathogens were used as indicator bacteria, and the antagonistic strains were identified from the 126 strains. The activities of exocrine digestive enzymes in the strains were also tested. Four strains with antibacterial and digestive enzyme activities were obtained and the best strains, Bacillus subtilis Y2 and Bacillus amyloliquefaciens Y9, were selected according to their ability to protect epithelial cells from infection. In addition, the effects of strains Y2 and Y9 at the individual level were investigated, finding that the activities of the immune-related enzymes superoxide dismutase, catalase, acid phosphatase, and peroxidase were significantly increased in the sera of the treatment group compared with the control group (p < 0.05). The specific growth rate (SGR, %) was also increased, especially in the Y2 group, and was significantly higher compared with the controls (p < 0.05). The result of the artificial infection test showed that the cumulative mortality within 72 h in the Y2 group was the lowest (50.5%), and in the Y9 group (68.5%) it was significantly lower than that in the control group (100%) (p < 0.05). Analysis of the intestinal microbial communities indicated that Y2 and Y9 could alter the composition of the intestinal flora, increasing both species richness and evenness, and inhibiting the growth of Vibrio in the intestine. These results suggested food supplemented with Y2 and Y9 could improve both immune function and disease resistance, as well as have a positive effect on the growth performance and the intestinal morphology of C. semilaevis.

Commensal Bacillus siamensis LF4 induces antimicrobial peptides expression via TLRs and NLRs signaling pathways in intestinal epithelial cells of Lateolabrax maculatus

Antimicrobial peptides (AMPs) play an important role in modulating intestinal microbiota, and our previous study showed that autochthonous Baccilus siamensis LF4 could shape the intestinal microbiota of spotted seabass (Lateolabrax maculatus). In the present study, a spotted seabass intestinal epithelial cells (IECs) model was used to investigate whether autochthonous B. siamensis LF4 could modulate the expression of AMPs in IECs. And then, the IECs were treated with active, heat-inactivated LF4 and its supernatant to illustrate their AMPs inducing effects and the possible signal transduction mechanisms. The results showed that after 3 h of incubation with 10⁸ CFU/mL B. siamensis LF4, lactate dehydrogenase (LDH), glutamic oxaloacetic transaminase (GOT), glutamic propylic transaminase (GPT) activities in supernatant decreased significantly and obtained minimum values, while supernatant alkaline phosphatase (AKP) activity, β-defensin protein level and IECs Na⁺/K⁺-ATPase activity, AMPs (β-defensin, hepcidin-1, NK-lysin, piscidin-5) genes expression increased significantly and obtained maximum values (P < 0.05). Further study demonstrated that the active, heat-inactivated LF4 and its supernatant treatments could effectively decrease the LDH, GOT, and GPT activities in IECs supernatant, increase AKP activity and β-defensin (except LF4 supernatant treatment) protein level in IECs supernatant and Na⁺/K⁺-ATPase and AMPs genes expression in IECs. Treatment with active and heat-inactivated B. siamensis LF4 resulted in significantly up-regulated the expressions of TLR1, TLR2, TLR3, TLR5, NOD1, NOD2, TIRAP, MyD88, IRAK1, IRAK4, TRAF6, TAB1, TAB2, ERK, JNK, p38, AP-1, IKKα, IKKβ and NF-κB genes. Treatment with B. siamensis LF4 supernatant also resulted in up-regulated these genes, but not the genes (ERK, JNK, p38, and AP-1) in MAPKs pathway. In summary, active, heat-inactivated and supernatant of B. siamensis LF4 can efficiently induce AMPs expression through activating the TLRs/NLRs-MyD88-dependent signaling, active and heat-inactivated LF4 activated both the downstream MAPKs and NF-κB pathways, while LF4 supernatant only activated NF-κB pathway.

Chemical composition and biological activities of the essential oils from Lippia alba and Lippia origanoides

There is an increasing interest in essential oils extracted from Verbenaceae plant species as potential sources of biologically active compounds that could provide a starting point for designing novel phyto-pharmaceuticals in aquaculture. The present study was aimed to investigate the chemical composition, antioxidant activity, acute toxicity and antimicrobial effects against Vibrio parahaemolyticus of essential oils extracted from Lippia alba and L. origanoides. Approximately 23 components were identified and quantified by gas chromatography-mass spectrometry and flame ionization detection in each species' essential oil. The most predominant compounds were geranial (23.0%), limonene (17.0%) and neral (15.5%) in L. alba, and thymol (47.2%), p-cymene (16.0%) and E-caryophyllene (11.3%) in L. origanoides. The essential oils have antibacterial activity against Vibrio parahaemolyticus presenting Minimum Inhibitory Concentration (MIC) and Bactericidal Concentration (MBC) values between 156-625 µg mL-1. The essential oils also show antioxidant potential estimated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assays, presenting IC50 of 60.16 mg mL-1 and 0.22 mg mL-1 for L. alba and L. origanoides EO, respectively. Both oils were classified as toxic to Artemia salina nauplii. Therefore, these essential oils may be useful for controlling pathogenic bacteria important to the aquaculture industry.

Silver nano/microparticle toxicity in the shrimp Litopenaeus vannamei (Boone, 1931)

The effects of silver nano/microparticles (AgP) on juvenile Litopenaeus vannamei shrimp were evaluated through several responses, aiming to use it as a prophylactic and therapeutic method. Shrimps (3.19 ± 0.13 g) were exposed to clear water for 3 h with increasing concentrations of nanosilver (0; 25; 100; and 400 μg/l). After 3 h of exposure, they were transferred to water without nanosilver for 30 days (recovery). The weight gain and weekly growth were not affected by AgNP. Total antioxidant capacity (ACAP) increased in the hepatopancreas (exposure period) and gills (recovery) in shrimp exposed to AgNP. In muscle, ACAP was induced in shrimp exposed to 100 μg/l AgNP (exposure). In the gills, there was an increase in TBARS in shrimp exposed to 100 μg/l AgNP (recovery). In the concentration of protein-associated sulfhydryl groups (P-SH), a decrease was observed in the hepatopancreas (recovery) in the 100 μg/l AgNP treatment. In chromaticity parameters, an increase in reddish tones was observed in shrimp exposed to 100 μg/l AgNP (recovery). An increase in granular hemocytes was verified in shrimp exposed to 25 and 400 μg/l AgNP during exposure. Tissues analyzed histologically showed normal patterns without apoptosis or necrosis processes, and after 30 d of recovery, only in one muscle sample of shrimp exposed to μg/l of AgNP was silver detected. It is concluded that a prophylactic action of short duration (3 h) mostly did not affected the welfare of shrimp L. vannamei and can be considered its use as a therapeutic strategy.

Enhancement of growth, survival, immunity and disease resistance in Litopenaeus vannamei, by the probiotic, Lactobacillus plantarum Ep-M17

Green ecological prevention and control technology is a hot spot for aquatic disease research in recent years, and lactic acid bacteria is an important type of probiotic widely used in aquaculture. In this study, a strain of Lactobacillus plantarum Ep-M17 was isolated from the intestine of healthy grouper, which showed good antibacterial activity in vitro. To investigate the application prospects of Ep-M17 as a probiotic, we added it to the diet and fed Litopenaeus vannamei, and then detected its influence on the growth performance, survival rate, disease resistance, intestinal tissue structure, gene transcription, and the flora in the gut of shrimp. The results showed that feeding Ep-M17 increased the specific growth rate, reduced the feed conversion rate, improved the survival rate, and achieved a 76.9% relative protection rate after Vibrio parahaemolyticus E1 infection in shrimp. Histological examination displayed that Ep-M17-fed shrimp had a thick intestinal villi layer, which enhanced the protection against pathogen damage. It was also found that Ep-M17 significantly increased the activity levels of immune and digestion-related enzymes SOD, CAT, TRY, AKP, LIP, and AMS in the gut of shrimp, especially after V. parahaemolyticus E1 infection, these enzymes increased significantly higher than that of control. Transcriptome analysis revealed that Ep-M17 activated significantly differential expression of genes in immune, nutritional, metabolic, and Signal Transduction-related pathways in the gut of shrimp. In addition, Ep-M17 enriched the bacterial diversity of the shrimp gut, with a significant increase in many low-abundance bacterial species, a significant decrease in the number of pathogenic bacteria like Vibrio, and a significant increase in the number of beneficial bacteria. The above results evaluated that Ep-M17 as a potential probiotic can promote the growth and improve the disease resistance of shrimp by regulating the nutritional immune response and flora of the intestine.

Vibriosis Outbreaks in Aquaculture: Addressing Environmental and Public Health Concerns and Preventive Therapies Using Gilthead Seabream Farming as a Model System

Bacterial and viral diseases in aquaculture result in severe production and economic losses. Among pathogenic bacteria, species belonging to the Vibrio genus are one of the most common and widespread disease-causing agents. Vibrio infections play a leading role in constraining the sustainable growth of the aquaculture sector worldwide and, consequently, are the target of manifold disease prevention strategies. During the early, larval stages of development, Vibrio species are a common cause of high mortality rates in reared fish and shellfish, circumstances under which the host organisms might be highly susceptible to disease preventive or treatment strategies such as vaccines and antibiotics use, respectively. Regardless of host developmental stage, Vibrio infections may occur suddenly and can lead to the loss of the entire population reared in a given aquaculture system. Furthermore, the frequency of Vibrio-associated diseases in humans is increasing globally and has been linked to anthropic activities, in particular human-driven climate change and intensive livestock production. In this context, here we cover the current knowledge of Vibrio infections in fish aquaculture, with a focus on the model species gilthead seabream (Sparus aurata), a highly valuable reared fish in the Mediterranean climatic zone. Molecular methods currently used for fast detection and identification of Vibrio pathogens and their antibiotic resistance profiles are addressed. Targeted therapeutic approaches are critically examined. They include vaccination, phage therapy and probiotics supplementation, which bear promise in supressing vibriosis in land-based fish rearing and in mitigating possible threats to human health and the environment. This literature review suggests that antibiotic resistance is increasing among Vibrio species, with the use of probiotics constituting a promising, sustainable approach to prevent Vibrio infections in aquaculture.

Competitive Exclusion Bacterial Culture Derived from the Gut Microbiome of Nile Tilapia (Oreochromis niloticus) as a Resource to Efficiently Recover Probiotic Strains: Taxonomic, Genomic, and Functional Proof of Concept

This study aims to mine a previously developed continuous-flow competitive exclusion culture (CFCEC) originating from the Tilapia gut microbiome as a rational and efficient autochthonous probiotic strain recovery source. Three isolated strains were tested on their adaptability to host gastrointestinal conditions, their antibacterial activities against aquaculture bacterial pathogens, and their antibiotic susceptibility patterns. Their genomes were fully sequenced, assembled, annotated, and relevant functions inferred, such as those related to pinpointed probiotic activities and phylogenomic comparative analyses to the closer reported strains/species relatives. The strains are possible candidates of novel genus/species taxa inside Lactococcus spp. and Priestia spp. (previously known as Bacillus spp.) These results were consistent with reports on strains inside these phyla exhibiting probiotic features, and the strains we found are expanding their known diversity. Furthermore, their pangenomes showed that these bacteria have indeed a set of so far uncharacterized genes that may play a role in the antagonism to competing strains or specific symbiotic adaptations to the fish host. In conclusion, CFCEC proved to effectively allow the enrichment and further pure culture isolation of strains with probiotic potential.

Evaluation of Salipiger thiooxidans and Exiguobacterium aestuarii from the Saemangeum Reservoir as Potential Probiotics for Pacific White Shrimp (Litopenaeus vannamei)

In this study, two bacterial species, Salipiger thiooxidans and Exiguobacterium aestuarii, were extracted and screened from the Saemangeum Reservoir. This study examined these species’ suitability as a probiotic by confirming the effects of S. thiooxidans and E. aestuarii added to rearing water for L. vannamei. Three experimental groups were evaluated for 6 weeks: (1) a control group reared in natural (i.e., untreated) water (CON), (2) an experimental group in which S. thiooxidans was added to natural water (SMG-A), and (3) natural water inoculated with E. aestuarii (SMG-B). The SMG-B group inoculated with E. aestuarii showed significantly higher final body weight, weight gain, specific growth rates, and feed efficiency than the control group. The SMG-B group inoculated with E. aestuarii exhibited significantly higher levels of serum lysozyme, and ACP and ALP activity than the control and SMG-A groups. The SMG-A and SMG-B groups inoculated with probiotics showed significantly lower total ammonia nitrogen and nitrite than the control group. Our findings suggest that S. thiooxidans and E. aestuarii extracted from the Saemangeum Reservoir can improve the water quality of aquaculture water, and, in particular, E. aestuarii is a potential probiotic for L. vannamei.

Gastrointestinal Microbiota of Spiny Lobster: A Review

The gastrointestinal (GI) microbiota is a group of complex and dynamic microorganisms present in the GI tract of an organism that live in symbiosis with the host and benefit the host with various biological functions. The communities of GI microbiota are formed by various aerobic, anaerobic, and facultatively anaerobic bacteria in aquatic species. In spiny lobsters, common GI microorganisms found in the GI tract are Vibrio, Pseudomonas, Bacillus, Micrococcus, and Flavobacterium, where the structure and abundance of these microbes are varied depending on the environment. GI microbiotas hold an important role and significantly affect the overall condition of spiny lobsters, such as secreting digestive enzymes (lipase, protease, and cellulase), helping in digesting food intake, providing nutrition and synthesising vitamins needed by the host system, and protecting the host against infection from pathogens and diseases by activating an immune mechanism in the GI tract. The microorganisms in the water column, sediment, and diet are primarily responsible for altering, manipulating, and shaping GI microbial structures and communities. This review also highlights the possibilities of isolating the indigenous GI microbiota as a potential probiotic strain and introducing it to spiny lobster juveniles and larvae for better health management.

Agavin induces beneficial microbes in the shrimp microbiota under farming conditions

Prebiotics and probiotics have shown a number of beneficial impacts preventing diseases in cultured shrimps. Complex soluble carbohydrates are considered ideal for fostering microbiota biodiversity by fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPS). Here we evaluated the growth performance and microbiota composition of the white shrimp Litopenaeus vannamei after dietary intervention using agavin as a FODMAP prebiotic under farming conditions. Adult L. vannamei were raised at a shrimp farm and the effect of agavin supplemented at 2% (AG2) or 10% (AG10) levels were compared to an agavin-free basal diet (BD). After 28 days-trial, the feed conversion ratio, total feed ingested, and protein efficiency ratio was significantly improved on animals fed with AG2. At the same time, no effect on growth performance was observed in AG10. Surprisingly, after sequencing the V3-V4 regions of the 16S rRNA gene a higher microbial richness and diversity in the hepatopancreas and intestine was found only in those animals receiving the AG10 diet, while those receiving the AG2 diet had a decreased richness and diversity, both diets compared to the BD. The beta diversity analysis showed a clear significant microbiota clustering by agavin diets only in the hepatopancreas, suggesting that agavin supplementation had a more substantial deterministic effect on the microbiota of hepatopancreas than on the intestine. We analyzed the literature to search beneficial microbes for shrimp's health and found sequences for 42 species in our 16S data, being significantly increased Lactobacillus pentosus, Pseudomonas putida and Pseudomonas synxantha in the hepatopancreas of the AG10 and Rodopseudomonas palustris and Streptococcus thermophiles th1435 in the hepatopancreas of the AG2, both compared to BD. Interestingly, when we analyzed the abundance of 42 beneficial microbes as a single microbial community "meta-community," found an increase in their abundance as agavin concentration increases in the hepatopancreas. In addition, we also sequenced the DNA of agavin and found 9 of the 42 beneficial microbes. From those, Lactobacillus lactis and Lactobacillus delbrueckii were found in shrimps fed with agavin (both AG2 and AG10), and Lysinibacillus fusiformis in AG10 and they were absent the BD diet, suggesting these three species could be introduced with the agavin to the diet. Our work provides evidence that agavin supplementation is associated with an increase of beneficial microbes for the shrimp microbiota at farming conditions. Our study provides the first evidence that a shrimp prebiotic may selectively modify the microbiota in an organ-dependent effect.

New bacilli-based probiotic for aquaculture: efficacy study on Macrobrachium rosenbergii

The data on the study of the effectiveness of a new probiotic based on strains B. toyonensis B-13249 and B. pumilus B-13250 when growing shrimps are presented. The experiments were carried out on a private farm in Kazakhstan. The control group of shrimps, which did not receive the probiotic, completed the molting process on the 28th day of the experiment, and the experimental group – 10 days earlier. It was also found that the probiotic has a positive effect on the hydrochemistry of water in recirculating aquaculture system (RAS). The concentration of ammonium (NH3/NH4 +), nitrite (NO2) and nitrate (NO3-) nitrogen in the experimental group did not reach the limit value, in contrast to the control. Based on the obtained results, this probiotic can be recommended for greening aquaculture. The dosage of the probiotic when applied with brine shrimp as feed for shrimp is 1 g/100 g of dry cysts. The dosage of the probiotic when the RAS is added to the water is 5 g/600 l of circulating water once a week.

Screening of antibacterial activities of Bacillus spp. isolated from the Parangkusumo coastal sand dunes, Indonesia

Background: The emergence of multidrug-resistant bacteria because of poor understanding of the issue and the misuse of antibiotics has become global health concern. Therefore, the discovery of novel antibacterial drugs is urgently needed. New antibacterial compounds may be found in the Bacillus species, which are abundant in sand dune ecosystems. Herein, we examined samples from the Parangkusumo coastal sand dunes in Indonesia.Methods: Samples were collected from three areas in the sand dunes (the area closest to the sea, the core area of sand dunes, and the area farthest from the sea). The samples were inoculated on Luria Bertani agar. Morphological and molecular identification was performed on the basis of 16S rRNA. The samples’ antimicrobial activity was evaluated with the disc diffusion method and compared with that of opportunistic pathogenic bacteria.Results: Five species of Bacillus were successfully isolated from the Parangkusumo coastal sand dunes. To our knowledge, this is the first report of the isolation of Bacillus aryabhattai in Indonesia. All samples showed antimicrobial activity against pathogenic bacteria. B. velezensis and B. subtilis showed antibacterial activity against Gram-positive bacteria, whereas B. aryabhattai and B. megaterium showed antibacterial activity against Gram-negative bacteria, and B. spizizenii showed antibacterial activity toward Gram-positive and Gram-negative bacteria.Conclusion: Five Bacillus species were successfully isolated from the Parangkusumo coastal sand dunes, Indonesia, and all samples showed antimicrobial activity toward opportunistic pathogenic bacteria. The crude antimicrobial compounds from B. megaterium, B. aryabhattai, B. subtilis, and B. spizizenii showed the highest growth-inhibition activity against E. coli, P. aeruginosa, B. cereus, and S. aureus, respectively.

Metagenomics in bioflocs and their effects on gut microbiome and immune responses in Pacific white shrimp

Biofloc systems generate and accumulate microbial aggregates known as bioflocs. The presence of bioflocs has been shown to change gut bacterial diversity and stimulate innate immunity in shrimp. The microbial niche of bioflocs may therefore have the potential to drive shifts in the shrimp gut microbiota associated with stimulation of innate immunity. We performed shotgun metagenomic analysis and 16S rRNA-based amplicon sequencing to characterize complex bacterial members in bioflocs and the shrimp digestive tract, respectively. Moreover, we determined whether biofloc-grown shrimp with discrete gut microbiomes had an elevation in local immune-related gene expression and systemic immune activities. Our findings demonstrated that the bacterial community in bioflocs changed dynamically during Pacific white shrimp cultivation. Metagenomic analysis revealed that Vibrio comprised 90% of the biofloc population, while Pseualteromonas, Photobacterium, Shewanella, Alteromonas, Bacillus, Lactobacillus, Acinetobacter, Clostridium, Marinifilum, and Pseudomonas were also detected. In the digestive tract, biofloc-grown shrimp maintained the presence of commensal bacteria including Vibrio, Photobacterium, Shewanella, Granulosicoccus, and Ruegeria similar to control shrimp. However, Vibrio and Photobacterium were significantly enriched and declined, respectively, in biofloc-grown shrimp. The presence of bioflocs upregulated immune-related genes encoding serine proteinase and prophenoloxidase in digestive organs which are routinely exposed to gut microbiota. Biofloc-grown shrimp also demonstrated a significant increase in systemic immune status. As a result, the survival rate of biofloc-grown shrimp was substantially higher than that of the control shrimp. Our findings suggested that the high relative abundance of vibrios in bioflocs enriched the number of vibrios in the digestive tract of biofloc-grown shrimp. This shift in gut microbiota composition may be partially responsible for local upregulation of immune-related gene expression in digestive organs and systemic promotion of immune status in circulating hemolymph.

White spot syndrome virus (WSSV) disturbs the intestinal microbiota of shrimp (Penaeus vannamei) reared in biofloc and clear seawater

White spot syndrome virus (WSSV) is one of the most virulent pathogens afflicting shrimp farming. Understanding its influence on shrimp intestinal microbiota is paramount for the advancement of aquaculture, since gut dysbiosis can negatively impact shrimp development, physiology, and immunological response. Thereupon, the data presented herein assesses the influence of WSSV infection and different rearing systems on the intestinal microbiota of Penaeus vannamei. Our study aimed to describe and correlate the composition of shrimp (Penaeus vannamei) gut microbiota, when reared in biofloc and clear seawater, before and (48 h) after WSSV experimental infection. Shrimp were kept in two different systems (biofloc and clear seawater) and experimentally infected with WSSV. Intestine and water samples were characterized by 16S rRNA gene sequencing, before and after viral infection. We observed (i) WSSV induced higher mortality among shrimp reared in biofloc; (ii) WSSV led to a loss of intestinal microbiota heterogeneity, at the genus level, in shrimp kept in clear seawater; (iii) there was a prevalence of Cetobacterium and Bacillus in the intestine of shrimp from both systems; (iv) WSSV did not cause significant changes in intestinal microbiota diversity or richness; (v) regardless of the type of system and time of infection, intestinal microbiota was dissimilar to that of the surrounding water, despite being influenced by the type of system. Therefore, WSSV infection leads to punctual dysbiotic changes in shrimp microbiota, although the virus is sufficiently virulent to cause high mortalities even in well-managed systems, such as a balanced experimental biofloc system. KEY POINTS: • WSSV infection leads to a perturbed gut microbiota in shrimp. • WSSV infection greater impacts microbiota of shrimp reared in CSW than those in BFT. • WSSV infection caused higher mortality levels in shrimp reared in BFT than in CSW. • Rearing system influences shrimp gut microbiota composition. Graphical abstract.

Effects of an exopolysaccharide from Lactococcus lactis Z-2 on innate immune response, antioxidant activity, and disease resistance against Aeromonas hydrophila in Cyprinus carpio L

Microbial exopolysaccharides (EPS) from Lactococcus have been found to have an important role in the probiotic activity of this bacterium; however, the immunomodulatory and antioxidant activities have not been fully explored in aquaculture. In the present study, we investigated EPS-2 from Lactococcus lactis Z-2, isolated from healthy common carp, for its immunomodulatory and antioxidant effects and disease resistance against Aeromonas hydrophila in Cyprinus carpio L. We found that the molecular weight of EPS-2 was 18.65 KDa. The monosaccharide composition of this polymer was rhamnose, xylose, mannose, glucose, and galactose at a molar percentage of 13.3%, 14.1%, 18.5%, 27.4%, and 26.7%, respectively. EPS-2 treatment could modulate the immune responses in vitro and in vivo. In vitro tests showed that EPS-2 could significantly enhance the proliferation and phagocytosis activities (P < 0.05) as well as induce the production of nitic oxide (NO), pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), and anti-inflammatory cytokines (IL-10, TGF-β) (P < 0.05) in head kidney cells. When the fish were gavaged with three different concentrations of EPS-2 (250, 500, 1000 μg/mL) for 7 days and infected with A. hydrophila, different expression patterns of the NO, cytokines, lysozyme (LZM), and alkaline phosphatase (AKP) in the serum and of antioxidants (T-AOC, SOD, CAT, GSH, GSH-Px and MDA) in hepatopancreas were observed. Before infection with A. hydrophila, EPS-2 supplementation significantly up-regulated the NO production, protein levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), LZM and AKP activities, and levels of antioxidant molecules compared to those in the negative (G1) group (P < 0.05), whereas levels of NO and pro-inflammatory cytokines and LZM and AKP activities were significantly lower than those in the positive (G2) group after infection (P < 0.05). However, whether infected or not, the expression levels of anti-inflammatory cytokines (IL-10, TGF-β) were significantly increased in the EPS-2 treatment groups (P < 0.05). These results indicate that EPS-2 has immunomodulatory and antioxidant effects on common carp, both in vitro and/or in vivo, and can be applied as a common carp feed supplement to enhance fish immunity and disease resistance against A. hydrophila.

Vibrio harveyi: A brief survey of general characteristics and recent epidemiological traits associated with climate change

Here we briefly review the major characteristics of the emerging pathogen Vibrio harveyi and discuss survival strategies and adaptation mechanisms underlying the capacity of this marine bacterium to thrive in natural and artificial aquatic settings. Recent studies suggest that some adaptation mechanisms can easily be acquired by V. harveyi and other members of the Vibrionaceae family owing to efficient horizontal gene transfer and elevated mutation rate. While discussing the main factors in charge of the expansion of Vibrio spp. habitats and concomitant spread of Vibrio-associated diseases under climate change, this review highlights the need for future studies able to address the joint impact of environmental and anthropogenic factors on the long-term dynamics and virulence of V. harveyi populations at the global scale.