Intestine Of Tilapia Research Articles

Comparison of Pediococcus pentosaceus YC64-fermented soybean meal and raw soybean meal in diets for Nile tilapia: Growth performance, feed utilization, and intestine health

Fermentation is a promising approach for improving the utilization of soybean meal (SM) by aquaculture fish, and the strain is the core of microbial fermentation processes. Herein, Pediococcus pentosaceus YC64, an autochthonous probiotic isolated from the intestine of Nile tilapia (Oreochromis niloticus), was applied to the fermentation of raw SM. In an eight-week feeding trial, tilapia juveniles were divided into two treatments fed on diets with 0 % (Control) and 100 % of SM protein replaced by fermented SM (FSM). Results showed that solid-state fermentation improved SM quality indicated by increased acid-soluble protein contents. Fish fed the FSM diet had significantly higher weight gain, feed efficiency, and protein efficiency compared to those fed the SM diet. Furthermore, whole-body protein content significantly increased in the FSM-fed fish, accompanied with the increased amino acid transport and reduced protein catabolism. Texture profile analysis indicated that fish fed the FSM diet had reduced muscle hardness compared with the control, which was associated with changes in collagen deposition and myofiber development. Moreover, feeding an FSM diet enhanced goblet cell proliferation and stimulated mucin secretion, ultimately leading to improved intestinal tight junctions and reduced inflammatory response. Besides, the FSM diet feeding altered intestinal microbiota community, characterized by increased abundance of Pediococcus. Overall, P. pentosaceus YC64 exhibits promise as a fermentation strain in the production of FSM. The FSM performed better than SM in improving the growth performance, feed utilization, and intestine health of Nile tilapia.

Evaluation of antibacterial activity and susceptibility antibiotics of native lactic acid bacteria from tilapia (Oreochromis niloticus) in Ivory Coast

Lactic Acid Bacteria probiotics play a crucial role in improving aquaculture productivity however, their use required beforehand a rigorous selection. This study appeared as a preliminary research in LAB potential probiotics selection. The aim of study was to select LAB strains potentially probiotic isolated from gut intestine of tilapia (Oreochromis niloticus) based on antibacterial activity and susceptibility antibiotics tests. The antibacterial activity was carried by agar well diffusion method against five pathogen indicators (E. coli ATCC 25922, K. pneumoniae ATCC 43816, P. aeruginosa ATCC 27853, P. mirabilis JCM1669, and S. aureus ATCC 25913). The susceptibility antibiotic test was performed by disc diffusion method by 12 antibiotics use. Seventy-two (72) from 154 LAB isolates completed the antibacterial activity test. With 79.08% inhibition, S. aureus was the pathogen most inhibited, whereas E. coli had the least inhibition, at 61.44%. In terms of antibiotic susceptibility testing, out of the 72 LAB isolates from earlier studies, only 25 LAB isolates demonstrated resistance to ciprofloxacin, gentamycin, and oxacillin and sensitivity to nine out of the twelve antibiotics employed. The 25 LAB isolates seemed suitable candidates for more probiotic tests.

Heterogeneous bacterial communities in gills and intestine of Nile tilapia (Oreochromis niloticus) and in water and sediments of aquaculture ponds in Bangladesh

Tilapia aquaculture contributes significantly to the nutritional requirements of humans. Because microbes play a pivotal role in maintaining the host's physiology and biochemistry, research on the microbiomes associated with tilapia and in the rearing pond water and sediment can contribute to increased production. We applied 16S rRNA gene amplicon sequencing to elucidate the bacterial community structures in the gills and intestine of Nile tilapia as well as in the water and sediment of their rearing ponds. We identified a total of 9770 bacterial Operational Taxonomic Units (OTUs) in all the samples. The sediment samples, which generated 3884 unique OTUs, had the highest level of alpha-diversity (Shannon index, P < 0.01) among all the samples. Fusobacteria (59%) predominated and constituted the indicator phylum in tilapia gills, while Proteobacteria was prevailed in water (52%), sediment (28%), and intestine (33%). The bacterial community structures of the gills and intestine were not much similar to those of the surrounding water and sediment, probably due to host-specific microbial selection. More than 70% of the bacterial flora were beneficial, whereas nearly 10% were pathogenic in gills and intestine of tilapia. This study aims to explore the microbiome of tilapia aquaculture in Bangladesh, and the results suggest that the microbial communities in tilapia gills and intestine are in a eubiotic state, which indicates a healthy state for better growth and production of Nile tilapia aquaculture.

Screening and effects of intestinal probiotics on growth performance, gut health, immunity, and disease resistance of Nile tilapia (Oreochromis niloticus) against Streptococcus agalactiae

In the present study, 59 autochthonous bacteria were isolated from the intestine of tilapia. Following enzyme producing activity, antagonistic ability, hemolytic activity, drug sensitivity assessments, and in vivo safety evaluation, 7 potential probiotic strains were screened out: Bacillus tequilensis BT0825-2 (BT), Bacillus aryabhattai BA0829-3 (BA1), Bacillus megaterium BM0505-6 (BM), Bacillus velezensis BV0505-11 (BV), Bacillus licheniformis BL0505-18 (BL), B. aryabhattai BA0505-19 (BA2), and Lactococcus lactis LL0306-15 (LL). Subsequently, tilapia were fed basal diets (CT) and basal diets supplemented with 108 CFU/g of BT, BA1, BM, BV, BL, BA2 and LL, respectively. After 56 days of continuous feeding, the growth parameters (weight gain, final weight, and specific growth rate) showed significant improvement (p < 0.05) in both BM and BA2 groups. The total cholesterol and triglycerides of serum were significantly decreased in BV and LL groups (p < 0.05). The superoxide dismutase, glutathione reductase, and lysozyme of BV, BA2 and LL groups were increased, and the malondialdehyde of BV group was significantly decreased. The villous height and amylase of midgut were increased in BV, BA2 and LL groups. In addition, the expression levels of ZO-1 and occludin genes in the midgut of tilapia were enhanced in BM, BV, BA2 and LL groups. The supplementation of probiotics reduced the abundance of Cyanobacteria and increased the abundance of Actinobacteria at the phylum level. At the genus level, the addition of probiotics increased the abundance of Romboutsia. Furthermore, improvement in the expression of immune-related genes were observed, including interleukin 1β, interleukin 10, tumor necrosis factor alpha, and transforming growth factor beta (p < 0.05). After challenging with S. agalactiae, the survival rates of BV, BA2 and LL groups were significantly higher than CT group (p < 0.05). Above results indicated that BM, BA2, BV and LL improved growth performance, gut health or immunity of tilapia, which can be applied in tilapia aquaculture.

Effects of Dietary Bacillus amyloliquefaciens SCAU-070 (Based on a Woody Plant-Based Diet) on Antioxidation, Immune and Intestinal Microbiota of Tilapia (Oreochromis niloticus).

This study aimed to explore the effects of Bacillus amyloliquefaciens (BA) as one woody forage addition (as a probiotic, 1 × 107 CFU/g) on tilapia (Oreochromis niloticus). Woody forage is one kind of fishery feed that could significantly enhance the growth, feed utilization, and digestibility of tilapia. At first, tilapia was divided into eight groups and fed with control, control + BA, Moringa oleifera, M. oleifera + BA, Neolamarckia cadamba, N. cadamba + BA, Broussonetia papyrifera, and B. papyrifera + BA diets, respectively. After dieting for 8 weeks, the intestinal morphology of tilapia in the eight groups was observed, and the effects of the B. amyloliquefaciens addition and wordy forage on the intestine functions were analyzed by two-way ANOVA. As no significant negative effects were found on the woody forage on tilapia, the villus height, density and width, and epithelial goblet cells in the posterior intestines of tilapia with BA supplementation were greater than those in the groups without BA supplementation, suggesting B. amyloliquefaciens SCAU-070 could promote the growth and development of tilapia intestinal tracts. Furthermore, it was found that B. amyloliquefaciens SCAU-070 enhanced the antioxidation capacity of tilapia posterior intestine tissue by promoting the activity of superoxide dismutase and content of malondialdehyde. In addition, the result of high-throughput sequencing (16S rDNA) showed that the beneficial bacteria Cetobacterium and Romboutsia in the probiotic groups increased significantly, while the potential pathogenic bacteria Acinetobacter decreased significantly.

Uptake, tissue distribution, and biotransformation pattern of triclosan in tilapia exposed to environmentally-relevant concentrations

Although triclosan has been ubiquitously detected in aquatic environment and is known to have various adverse effects to fish, details on its uptake, bioconcentration, and elimination in fish tissues are still limited. This study investigated the uptake and elimination toxicokinetics, bioconcentration, and biotransformation potential of triclosan in Nile tilapia (Oreochromis niloticus) exposed to environmentally-relevant concentrations under semi-static regimes for 7 days. For toxicokinetics, triclosan reached a plateau concentration within 5-days of exposure, and decreased to stable concentration within 5 days of elimination. Approximately 50 % of triclosan was excreted by fish through feces, and up to 29 % of triclosan was excreted through the biliary excretion. For fish exposed to 200 ng·L−1, 2000 ng·L−1, and 20,000 ng·L−1, the bioconcentration factors (log BCFs) of triclosan in fish tissues obeyed similar order: bile ≈ intestine > gonad ≈ stomach > liver > kidney ≈ gill > skin ≈ plasma > brain > muscle. The log BCFs of triclosan in fish tissues are approximately maintained constants, no matter what triclosan concentrations in exposure water. Seven biotransformation products of triclosan, involved in both phase I and phase II metabolism, were identified in this study, which were produced through hydroxylation, bond cleavages, dichlorination, and sulfation pathways. Metabolite of triclosan-O-sulfate was detected in all tissues of tilapia, and more toxic product of 2,4-dichlorophenol was also found in intestine, gonad, and bile of tilapia. Meanwhile, two metabolites of 2,4-dichlorophenol-O-sulfate and monohydroxy-triclosan-O-sulfate were firstly discovered in the skin, liver, gill, intestine, gonad, and bile of tilapia in this study. These findings highlight the importance of considering triclosan biotransformation products in ecological assessment. They also provide a scientific basis for health risk evaluation of triclosan to humans, who are associated with dietary exposure through ingesting fish.

Dietary Protein Quality Affects the Interplay between Gut Microbiota and Host Performance in Nile Tilapia.

Dietary protein quality plays a key role in maintaining intestinal mucosal integrity, but also modulates the growth of luminal microorganisms. This work assessed the effect of dietary protein sources on the performance, gut morphology, and microbiome in Nile tilapia. Four isonitrogenous and isolipidic diets comprising equivalent amounts of the protein supply derived from either PLANT, ANIMAL, INSECT, or BACTERIAL (bacterial biomass) sources were fed to triplicate groups of fish (IBW: 12 g) for 46 days. Fish fed the ANIMAL and BACTERIAL diets showed significantly higher weight gains than those fed the PLANT and INSECT diets (p < 0.05). Relative abundance at the phylum level showed that Bacteroidetes, Fusobacteria, and Proteobacteria were the more abundant phyla in tilapia's intestine, while Cetobacterium was the most representative genus in all treatments. Interesting patterns were observed in the correlation between amino acid intake and genus and species abundance. Metabolism prediction analysis showed that BACTERIAL amine and polyamine degradation pathways are modulated depending on diets. In conclusion, different protein sources modulate the relationship between bacteria functional pathways and amino acid intake.

Ameliorative effect of BIO-MOS® as a dietary supplementation on growth performance, physiological response, oxidative status, and immunity-linked gene expression in Nile tilapia (Oreochromis niloticus) fingerlings challenged with Aeromonas hydrophila.

Mannanoligosaccharides (MOS) usage in fish production has drawn more attention because of their positive benefits on disease resistance and fish performance. The ongoing research was executed to assess the potential advantages of Bio-Mos® dietary supplementation regarding the growth outcomes, physiological response, oxidative biomarkers, and immunity-linked gene expression in Nile tilapia (Oreochromis niloticus) fingerlings exposed to bacterial infection with Aeromonas hydrophila. Four experimental diets were developed using a 30% protein baseline diet, with Bio-Mos® added at variable levels; 0.0, 0.5, 1, and 2 g/kg, respectively. 240 healthy Nile tilapia fingerlings were split into 4 groups at random and assigned to 12 glass aquariums (three replicates of 20 fish/treatment). Diets were admitted at a 3% rate of fish biomass/aquarium for 8 weeks. Following the feeding trial, fish from every treatment were intraperitoneally injected with pathogenic A. hydrophila, and then observed for 15 days to record the survival rate percent (SR%) post challenge. Results revealed significant improvement in growth performance, physiological response, immunological parameters (phagocytic index, phagocytic activity, and lysozyme), and antioxidant parameters [catalase, malondialdehyde, glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD)] among Bio-Mos® treated groups. Moreover, Bio-Mos® increased the expression of tumor necrosis factor alpha and Interleukin 1β, genes linked to the liver immune system. Growth-related genes (GHr), antioxidant-related genes (SOD and GSH-Px). In fish subjected to pathogens, dietary MOS supplementation could significantly lower oxidative stress, showing promise as a preventative supplement for Nile tilapia in place of antibiotics. On the other hand, Bio-Mos® considerably improved each of the three intestinal morphological measures (villus width, villus length, and crypt depth), showing the best overall intestinal structure-improving impact. The challenge with A. hydrophila caused marked degenerative alterations in the intestine, hepatopancreas, spleen, and posterior kidney of Nile tilapia, in the control group. However, lesion severity was greatly decreased and showed marked amelioration with an increased concentration of Bio-Mos®. The A. hydrophila-challenged groups revealed a 100% SR% mainly among the Bio-Mos® supplemented groups. It is recommended to enrich the Nile tilapia fingerlings diets with 2 g.kg-1 of MOS for better results on the growth rate, physiological response, immunological response, and intestinal absorptive capacity.

Characterisation of alkaline phosphatase from hepatopancreas and intestine of red tilapia (Oreochromis spp.) from Malaysia

Alkaline phosphatase (ALP) is an enzyme typically found in the liver and intestines of many organisms. High levels of ALP in a fish, indicate that the fish is either sick or has been exposed to heavy metals. In this study, ALP was purified from the hepatopancreas and intestine of red tilapia (Oreochromis spp.) using two main steps: ammonium sulphate precipitation and ion-exchange chromatography. Samples from the ion exchange step were analysed for ALP activities and characterized using SDS-PAGE. The SDS-PAGE analysis revealed two identical bands with ALP molecular weights of 68,000 Da (hepatopancreas) and 180,500 Da (intestine) components. Overall, the hepatopancreas and intestine purification folds acquired from the final step were 1.8 and 21.9, respectively, with recovery of only 0.22% (hepatopancreas) and 0.01%. (intestine). From the hepatopancreas and intestine, the specific activity of the enzyme was 1.72 X 10-2 mol-1 mg-1 and 2.93 X 10-1 mol-1 mg-1, respectively. ALP from the hepatopancreas was stable up to 50°C, while the optimal temperature for intestine enzyme ALP was 60°C. The ideal pH for ALP of Oreochromis spp.’s hepatopancreas and intestine was pH 10. The Li+, Na+, and K+ positive monovalent alkali metal ions have no impact on the action of the ALP enzyme. However, the enzyme actions are triggered by the positive divalent alkaline metal ions Mg2+ and Ca2+. The heavy metal ions, Zn2+, Cu2+, Cd2+, and Hg2+, were discovered to inhibit the action of the ALP enzyme. Overall, the identification of ALP would be helpful as a diagnostic instrument for determining the health and quality of fish.

Oligochitosan for mutual paddy and tilapia growth performance in aquaponics system

This study was conducted to evaluate the influence of oligochitosan added to the fish tank to benefit both tilapia and paddy in the aquaponics system. Chitosan was irradiated at 25 kGy to produce low molecular weight chitosan (oligochitosan). The characteristics of chitosan such as molecular weight, solubility, viscosity, and colour were investigated. The low molecular weight chitosan (Mw = 5 kDa), obtained from the radiation degradation by gamma-ray was further used as a dietary supplement for tilapia. Nitrogen, one of the most important macro-nutrients for plant growth and crop productivity was supplied by fish faeces and food waste containing oligochitosan in fish tanks. The addition of oligochitosan could improve growth, and immune responses and alter the bacterial flora in the intestine of tilapia, so as to play a role in promoting the growth of paddy in the aquaponics system.

Dietary supplementation of Patchouli oil increases the resistance against Streptococcus agalactiae infection in GIFT tilapia as revealed by transcriptome and 16s amplicon profiling

Large-scale disease outbreaks that caused by Streptococcus agalactiae (SA) infection have dramatically affected tilapia production worldwide. Patchouli oil (PO) is a traditional Chinese herbal medicine in treating gastrointestinal symptoms and is considered to be a safe and efficient candidate to treat SA infection in tilapia. In this study, we first investigated the changes of intestinal microbiota and host responses in GIFT tilapia after a 28-day dietary supplementation of different concentrations of PO (basic diet, 5 μL PO/g diet, or 15 μL PO/g diet) and followed by SA infection using an integrative analysis of transcriptome and 16 S amplicon profiling. We observed that dietary supplementation of 5 μL PO/g diet improved food intake and growth in tilapia. Histopathological observation confirmed there were increased surface area of intestinal villi and generally decreased ROS as revealed by the MAD, GSH-PX, and T-SOD activities in the tilapia intestines in response to dietary PO supplementation. The intestinal microbial diversities and community structures were significantly affected, and the colonization of probiotics (e.g., Cetobacterium and clostridium_ sensu_stricto_1) in the mucosa was improved in the dietary PO groups. The relative abundance of Streptococcus (0.033%) in the 15 μL PO/g dietary group was much lower than that in the control group (basic diet; 0.86%). A large number of DEGs were enriched in the immune-related pathways, e.g., lysosomal lumen, MHC protein complex, and toll-like receptor 2 signaling pathway. Our findings suggested that dietary supplementation of PO enhanced intestinal physical barriers, increased the colonization of probiotic bacteria and improved intestinal immunity in tilapia. This provides novel knowledge on PO as a dietary supplement to improve intestinal health against SA invasion in tilapia.

Antibacterial activity of lactic acid bacteria from various freshwater fish species against pathogenic bacteria in caged red tilapia (Oreochromis sp.)

Abstract. Quach VCT, Tran QD, Ha NH, Nguyen BT, Tu TD, Nguyen PT. 2023. Antibacterial activity of lactic acid bacteria from various freshwater fish species against pathogenic bacteria in caged red tilapia (Oreochromis sp.). Biodiversitas 24: 3373-3383. Antibiotic-resistant bacteria are a big challenge for many aquaculture countries around the world. The search for new solutions, such as probiotics to replace antibiotics in aquaculture, attracts the interest of many scientists. The investigation was accomplished by isolating Lactic Acid Bacteria (LAB) inhibiting Streptococcus agalactiae and Aeromonas hydrophila, which cause swollen eyes and hemorrhagic skin disease in caged red tilapia (Oreochromis sp.) in Vinh Long province. The findings isolated 37 isolates of LAB from the intestines of catfish, red tilapia, and tilapia. Using the diffusion well method, the results showed that 13/37 (35.14%) and 18/37 (48.65%) isolates were inhibitory against S. agalactiae and A. hydrophila, respectively. The research found that eight isolates were inhibitory to two species of S. agalactiae and A. hydrophila, especially isolate CT6.2, which has the strongest inhibition (10.5 mm inhibition zone diameter). Our finding revealed that the isolates CT6.2 and RP6 demonstrate the highest antagonistic activity against S. agalactiae and A. hydrophila at a density of 108 CFU/mL after incubation at 35°C, pH = 5-6 for 48-60 h. Using PCR techniques and 16S rRNA gene sequencing combined with morphological and biochemical characteristics, the LAB isolates in the findings belong to the genera Lactobacillus and Pediococcus, being 99.35% and 99.02% similar to Lactobacillus plantarum and Pediococcus pentosaceus, respectively. This is the first report on the antimicrobial activity of LAB against S. agalactiae and A. hydrophila in caged red tilapia in the Mekong Delta.

The characteristics of the intestinal bacterial community from Oreochromis mossambicus and its interaction with microbiota from artificial fishery habitats

BackgroundArtificial habitats can allow many fish to flock together and interact and have been widely used to restore and protect fishery resources. The piece of research intends to elucidate the relationship of microbial communities between tilapia (Oreochromis mossambicus) intestines and artificial fishery habitats (water and sediments). Hence, 16 S rDNA sequencing technology was used to study the bacterial communities from intestines, water, and sediments.ResultsThe results showed that the tilapia intestines had the lowest richness of Operational Taxonomic Units (OTUs) and the lowest diversity of the bacterial community compared to water and sediments. The intestine, water, and sediment microbial communities shared many OTUs. Overall, 663 shared OTUs were identified from the tilapia intestines (76.20%), the surrounding water (71.14%), and sediment (56.86%) in artificial habitats. However, there were unique OTUs that were detected in different sample types. There were 81, 77 and 112 unique OTUs observed in tilapia intestines, the surrounding water and sediment, respectively. Proteobacteria, Cyanobacteria, Actinobacteria, Firmicutes, Fusobacteria, and Bacteroidetes were the most common and dominant bacterial phyla between the tilapia intestines and habitats. In the two groups, the microbial communities were similar in the taxonomic composition but different in the abundance of bacterial phyla. Interestingly, Firmicutes increased, while Fusobacteria decreased in artificial habitats. These findings indicated that the artificial habitats had fewer effects on the water environment and indicated that the mode of artificial habitats could have an effect on the enriched bacteria in the tilapia intestines.ConclusionsThis study analysed the bacterial communities of artificial habitats from the intestines, water, and sediments, which can explain the relationship between the tilapia intestines and habitats and strengthen the value of ecological services provided by artificial habitats.

Interactive effects of cyclical fasting, refeeding, and dietary protein regimes on the growth performance, blood health, and intestinal histology of Nile tilapia (Oreochromis niloticus)

Diet composition and frequency of feeding are significant elements affecting the feeding cost and revenue of fish farming. Hence, this study evaluated the interactive effects of cyclical fasting, refeeding, and dietary protein regimes on the growth performance, blood health, intestinal histology, and economic efficiency of Nile tilapia. Fish were allocated into eight groups with triplicate glass aquaria; four groups received 30% protein, and four were fed on a 25% protein feed. Fish fed on 30% or 25% protein daily or after one, two, or three days. After one, two, or three days of feeding with 30% or 25% protein feed, fish were starved in a cycling fasting refeeding regime for 60 days. After this trial, no significant (P > 0.05) differences were found between tilapia refed 30% protein after three days and that fed on 25% protein continuously in terms of the growth performance and feed conversion ratio. Dietary protein levels, cyclical fasting and refeeding, and their interaction were significant (P < 0.05) factors on the lipase, alpha-amylase, and protease activity. The intestine of Nile tilapia showed normal histological structures, while the liver showed normal hepatocytes in the fish groups fed on 30% or 25% dietary protein daily or after one or two days. Tilapia refed 30% protein after one, two, and three days as well as those fed 25% protein daily or after one day had similar red blood cells (RBCs), hemoglobulin (Hb), and hematocrit (HCT) levels. The interactive effects of cyclical fasting, refeeding, and dietary protein regimes were significant (P < 0.05) factors in alanine transaminase (ALT), aspartate transaminase (AST), total protein, albumin, and globulin levels. The superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) were markedly higher in tilapia-fed on dietary 25% protein after one, two, or three days than in the remaining groups. Tilapia fed on dietary 25% protein daily or after one or two days had higher malondialdehyde (MDA) levels than those refed on dietary 30% after one, two, or three days. The economic efficiency recorded the highest value in tilapia fed on 30% protein daily (30%) without significant differences (P > 0.05) with those fed 25% dietary protein daily (28.23%) or after one day (27.44%). In summary, the results stated that Nile tilapia fasted and refed after one day with 30% could show compensated growth without interrupting the feed utilization and health status. Further, cyclical fasting, refeeding, and dietary protein (25% or 30%) regimes are economically feasible strategies for tilapia production.

Fish waste capped and colloidal nanosilver and its valorization as natural zeolite conjugates for application in aquaculture

The synthesis of silver nanoparticles has gained interest due to their diverse applications in various fields. It is very essential to use capping agents to avoid loss of nanosized characteristics due to agglomeration of AgNPs. In the present investigation, a simple and environmentally viable protocol to synthesize a wide range of concentrations of non-agglomerated and colloidal AgNPs using extracts of discarded wastes (gills and intestine) of Tilapia (Oreochromis mossambicus) in three different aqueous media without the requirement of any additional stabilizing and capping agent is described. The size of most of AgNPs ranged from 2 to 20 nm, followed by sizes of 20–40 nm and some with sizes of 40–50 nm. Zeta potential was in the range of −31.1 to −52.8 mV and −33.3 to −53.6 mV, and surface plasmon resonance ranged from 405 to 410 nm for gill and intestine extracts respectively. HR-TEM images indicated that Phosphate buffer saline is the best suitable for synthesizing non-agglomerated AgNPs capped with biomolecules. Valorization has been achieved by trapping Ag NPs into two different forms of natural zeolites namely stilbite and mordenite and their ammonia removal efficiency have been evaluated. In addition, the antimicrobial activity of synthesized AgNPs and their valorized products exhibited potent inhibitory activity against test bacteria such as Escherichia coli and Aeromonas hydrophila. This study not only establishes a simple and environmentally viable protocol for the synthesis of AgNPs and valorized products for environmental and disease management but also adds to the utilization of fish wastes in solid waste management.

Effects of enrofloxacin's exposure on the gut microbiota of Tilapia fish (Oreochromis niloticus)

Enrofloxacin (ENFX) has a broad-spectrum antibiotic activity, which is widely used in aquaculture. The effect of different ENFX exposure ways on the gut microbiota of tilapia is unclear. This study was conducted to investigate the effects of ENFX exposure on the gut microbiota of tilapia fish (Oreochromis niloticus). Three methods of ENFX exposure were selected: injection (IEG), oral administration (OEG) and soaking (SEG). After 48 h of exposure period, the intestine of tilapia was collected for high-throughput sequencing. PCoA analysis revealed a distinct clustering of control group, and which was located rather far away from ENFX exposure groups. The dominant phyla in the gut microbiota of tilapia fish were Proteobacteria, Actinobacteriota, Fusobacteria and Firmicutes. Compared to the control group, phylum Fusobacteriota was increased in SEG and IEG while decreased in OEG. ENFX treatment led to a decline in Corynebacterium, Clostridium sensu stricto_3 and Bacillus in treated fish compared with control fish, accompanied by an increase in Akkermansia, Ralstonia and Romboutsia. IEG had the least effect on gut microbiota of tilapia because it retained more microbes among treatment groups. Alpha- diversity decreased the most in SEG, but retained more probiotics such as Cetobacterium and Akkermansia. We assessed the effect of enrofloxacin on tilapia by changes in intestinal flora. The result indicated that either exposure method significantly reduced the diversity of tilapia gut microbiota. It may provide basic data for the scientific use of ENFX in aquaculture.

Isolation of Potential Probiotic Bacillus spp. from the Intestine of Nile Tilapia to Construct Recombinant Probiotic Expressing CC Chemokine and Its Effectiveness on Innate Immune Responses in Nile Tilapia.

This study aimed to investigate the potential probiotic Bacillus spp. from the intestine of Nile tilapia in order to construct a recombinant probiotic for the enhancement of the Nile tilapia immune response. One hundred bacterial isolates from the intestine of Nile tilapia were characterized for species identification using the 16s ribosomal RNA (rRNA). Only Bacillus isolates with exhibited antagonistic activity were investigated for their biological functions, which included protease-producing capacity, bile salts and pH tolerance, antibiotic susceptibility, and pathogenicity tests. According to the best results, Bacillus isolate B29, as closely related to B. subtilis, was selected to construct a recombinant probiotic for the delivery of CC chemokine protein (pBESOn-CC). The existence of recombinant probiotics was confirmed by Western blotting before the feeding trial. In addition, the CC chemokine mRNA level was quantified in the intestine of fish fed probiotics after 30 days of feeding. Total immunoglobulin, lysozyme activity, alternative complement 50 activity (ACH50), and phagocytic activity of fish fed either wild-type or recombinant probiotics were significantly increased, indicating that probiotics could stimulate the Nile tilapia immune system through different processes. Interestingly, the dietary supplementation of recombinant probiotics has a stronger immune response enhancement than the wild-type strain.

Omics analysis revealed the possible mechanism of streptococcus disease outbreak in tilapia under high temperature

High temperature is a main cause to result in the outbreak of tilapia streptococcal disease. However, the underlying mechanisms are not well understood. In this study, we first confirmed that tilapia infected with Streptococcus agalactiae (S. agalactiae) had a higher mortality at high temperature (35 °C) than that at normal temperature (28 °C). Subsequently, the effects of high temperature on gene expression pattern of S. agalactiae and intestinal microbiota of tilapia were respectively detected by RNA-seq and 16S rDNA sequencing. RNA-seq identified 357 differentially expressed genes (DEGs) in S. agalactiae cultured at 28 °C and 35 °C. GO and KEGG analysis showed that these DEGs were highly involved in metabolic processes, including glucose, lipid and amino acid metabolisms, which indicates that S. agalactiae have stronger vitality and are likely to be more infectious under high temperature. Microbiota analysis revealed that high temperature could influence the bacterial community composition of tilapia intestine, accompanied by changes in intestinal structure. Compared to feed at 28 °C, the total bacterial species as well as pathogens, such as norank_f__Rhizobiales_Incertae_Sedis, Pseudorhodoplanes, Ancylobacter, in tilapia intestine were significantly increased at 35 °C, which may weaken the immune resistance of tilapia. Taken together, our results suggest that high temperature evoked tilapia susceptible to S. agalactiae should be the combined effect of enhanced S. agalactiae metabolism and dysregulated tilapia intestinal microbiota.

Single-Cell Suspension Preparation from Nile Tilapia Intestine for Single-Cell Sequencing.

Nile tilapia is one of the most commonly cultured freshwater fish species worldwide and is a widely used research model for aquaculture fish studies. The preparation of high-quality single-cell suspensions is essential for single-cell level studies such as single-cell RNA or genome sequencing. However, there is no ready-to-use protocol for aquaculture fish species, particularly for the intestine of tilapia. The effective dissociation enzymes vary depending on the tissue type. Therefore, optimizing the tissue dissociation protocol by selecting the appropriate enzyme or enzyme combination to obtain enough viable cells with minimum damage is essential. This study illustrates an optimized protocol to prepare a high-quality single-cell suspension from Nile tilapia intestine with an enzyme combination of collagenase/dispase. This combination is highly effective for dissociation with the utilization of bovine serum albumin and DNase to reduce cell aggregation after digestion. The cell output satisfies the requirements for single-cell sequencing, with 90% cell viability and a high cell concentration. This protocol can also be modified to prepare a single-cell suspension from the intestines of other fish species. This research provides an efficient reference protocol and reduces the need for additional trials in the preparation of single-cell suspensions for aquaculture fish species.

Size-Dependent Uptake and Depuration of Nanoplastics in Tilapia (Oreochromis niloticus) and Distinct Intestinal Impacts.

Nanoplastics (NPs, <1 μm) are of great concern worldwide because of their high potential risk toward organisms in aquatic systems, while very little work has been focused on their tissue-specific toxicokinetics due to the limitations of NP quantification for such a purpose. In this study, NPs with two different sizes (86 and 185 nm) were doped with palladium (Pd) to accurately determine the uptake and depuration kinetics in various tissues (intestine, stomach, liver, gill, and muscle) of tilapia (Oreochromis niloticus) in water, and subsequently, the corresponding toxic effects in the intestine were explored. Our results revealed uptake and depuration constants of 2.70-378 L kg-1 day-1 and 0.138-0.407 day-1 for NPs in tilapia for the first time, and the NPs in tissues were found to be highly dependent on the particle size. The intestine exhibited the greatest relative accumulation of both sizes of NPs; the smaller NPs caused more severe damage than the larger NPs to the intestinal mucosal layer, while the larger NPs induced a greater impact on microbiota composition. The findings of this work explicitly indicate the size-dependent toxicokinetics and intestinal toxicity pathways of NPs, providing new insights into the ecological effects of NPs on aquatic organisms.