Modulation of innate immunity, expression of cytokine genes and disease resistance against Aeromonas hydrophila infection in goldfish (Carassius auratus) by dietary supplementation with Exiguobacterium acetylicum S01

Effects of Dietary Multi-Strain Probiotics on Growth Performance, Antioxidant Status, Immune Response, and Intestinal Microbiota of Hybrid Groupers (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂)

This study aims to examine the effects of the mixture of Bacillus cereus G1-11 and Exiguobacterium acetylicum G1-33, isolated from the gut of hybrid groupers (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂), on the host. The hybrid groupers were divided into a control (C, without any probiotics), B. cereus (BC, 1010 cfu/g), E. acetylicum (EA, 108 cfu/g), compound (mix, a 1:1 mixture of B. cereus and E. acetylicum), and positive reference group (P, Lactobacillus acidophilus, 5 × 108 cfu/L). Each group had four replicates, with 30 fish per replicate (53.30 ± 0.50 g), and were fed for 60 days. The results showed that adding probiotics to the feed significantly improved the weight gain, weight growth rate, specific growth rate, and digestive enzyme activities of hybrid groupers compared to the C group. The compound group was the most significant. In addition, composite probiotics added to feed significantly upregulated the expression levels of several growth-related genes in the liver and muscles. The activities of alkaline phosphatase, catalase, glutathione peroxidase, glutathione transferase, lysozyme, and total antioxidant capacity in the serum and liver were significantly influenced through mixed probiotic feeding. Moreover, the expression levels of several immune-related genes in the liver, spleen, and head kidney were significantly enhanced by adding single and mixed probiotics to feed, with the synergy of mixed probiotics being the best. An analysis of the gut microbiota showed that adding composite bacteria enhanced the richness and diversity of the gut microbiota, significantly increasing the relative abundance of potential probiotics (Cetobacterium and Microbacterium) while decreasing the presence of potential pathogens (Mycoplasma). Overall, our findings highlighted the efficacy of mixed probiotics (B. cereus and E. acetylicum) in enhancing growth performance, nutritional value of hybrid grouper feed, antioxidant capacity, immune response, and intestinal health, in finding the best combination of functional feed additives.

DNA vaccine incorporated poly (lactic-co-glycolic) acid (PLGA) microspheres offer enhanced protection against Aeromonas hydrophila infection

Encapsulation of DNA vaccines onto carriers enhances the immunogenicity of an antigen. Specifically, biodegradable polymers offer sustained release of vaccines which is crucial for any targeted delivery approach. Poly (lactic-co-glycolic) acid (PLGA) microspheres were used to load a DNA vaccine having a targeted gene of outer membrane protein (OMP) of Aeromonas hydrophila to clone and construct a DNA vaccine using a eukaryotic expression vector system (pVAX1-OMP DNA) and delivery in Carassius auratus against A. hydrophila infection. PLGA microspheres were prepared by emulsion technique oil-in-water and characterized by a High-Resolution Scanning Electron Microscope (HR-SEM). The results of PLGA-pVAX1-OMP DNA microspheres shows that average of 100-150 μm particle size and a loading efficiency (LE) of 68.8 %. Results indicate that C. auratus fed with PLGA-pVAX1-OMP DNA microspheres revealed a significant improvement in innate immune response, which includes, myeloperoxidase activity, respiratory burst and total immunoglobulin level compared with control group fish. The immune-related gene, IL1β, IL10, TGF, c-type, and g-type lysozyme also showed significantly higher expression after immunization. Furthermore, dietary supplementation of the PLGA-pVAX1-OMP DNA (G III) group exhibited a significantly higher survival rate (78 %) than the control group of fish. These results help us to understand the of mechanism of DNA vaccine administrated feed through PLGA nanoparticles resistance to infection by regulating systemic and innate immunity in Carassius auratus.

Gut-immunity modulation in Lepidocephalichthys guntea during Aeromonas hydrophila-infection and recovery assessed with transcriptome data

The fish immune system, which consists of innate and adaptive immunologic processes, defends against viruses, bacteria, fungi, and parasites. The gut immunity is an integral part of the host immune system that controls immunological homeostasis, hosts' interactions with their microbiomes, and provides defence against a number of intestinal infections. Lepidocephalichthys guntea, a facultative air-breathing fish, was experimentally infected with Aeromonas hydrophila using intraperitoneal injection followed by bath challenge, and transcriptome data were used to examine the gut immune responses during disease progression and recovery from the diseased state without the use of medication. For the control or uninfected fish (FGC) and the infected fish that were kept for seven days (FGE1) and fifteen days (FGE2), separate water tanks were set up. Coding DNA sequences (CDS) for FGC and FGE1, FGC and FGE2, and FGE1 and FGE2 were analyzed for differential gene expression (DGE). The presence and expression of genes involved in the T cell receptor (TCR) signalling pathway, natural killer (NK) cell-mediated cytotoxicity pathway, and complement-mediated pathway, along with a large number of other immune-related proteins, and heat shock protein (HSPs) under various experimental conditions and its relationship to immune modulation of the fish gut was the primary focus of this study. Significant up-and-down regulation of these pathways shows that, in FGE1, the fish's innate immune system was engaged, whereas in FGE2, the majority of innate immune mechanisms were repressed, and adaptive immunity was activated. Expression of genes related to the immune system and heat-shock proteins was induced during this host's immunological response, and this information was then used to build a thorough network relating to immunity and the heat-shock response. This is the first study to examine the relationship between pathogenic bacterial infection, disease reversal, and modification of innate and adaptive immunity as well as heat shock response.

Efficacy of dietary live or heat-killed Bacillus subtilis in goldfish (Carassius auratus) infected with Ichthyophthirius multifiliis

BACKGROUND

The beneficial effects of Bacillus subtilis on growth, immune response, and disease resistance against various diseases in different fish species have been proved. However, there are no data concerning this probiotic effect on skin mucosal immunity in fish infected with Ichthyophthirius multifiliis (Ich). Ich has a high mortality rate in both edible and ornamental fish and consequently is concerned with heavy economic losses.

OBJECTIVES

Thus, we assessed the efficacy of live and heat-killed B. subtilis on skin immunity and histopathology in goldfish (Carassius auratus) infected with Ich.

METHODS

Goldfish (144 fish, 2.38 g average weight) were stocked in nine glass tanks each in three replicates. Fish were fed 10⁹ CFU g^-1 live or heat-killed B. subtilis for 80 days.

RESULTS

Probiotic administration in both viable and non-viable forms could enhance the growth performance in goldfish. Probiotic therapy also reduced the density of the parasite and histopathological level on skin and gill tissues of the treated fish. Real-time polymerase chain reaction analysis showed a higher expression of lysozyme and tumour necrosis factor-α in the treated groups compared to the control group.

CONCLUSIONS

These data demonstrated the beneficial effect of B. subtilis as probiotic and paraprobiotic on growth performance and disease resistance to Ich infestation in goldfish.

Exopolysaccharides-Mediated ZnO Nanoparticles for the Treatment of Aquatic Diseases in Freshwater Fish Oreochromis mossambicus

Bacterial fish disease outbreaks are a key concern for aquaculture. Complementary feed additives such as immunostimulants can serve as an ideal solution for disease prevention. Herein, we scrutinized the efficacy of exopolysaccharides (EPSs) from probiotic Bacillus licheniformis and EPS-mediated zinc oxide nanoparticles (EPS-ZnO NPs) for a diet to evaluate growth parameters, antioxidant enzyme activities, and immune stimulation together with disease resistance against Aeromonas hydrophila and Vibrio parahaemolyticus in Mozambique tilapia Oreochromis mossambicus. Fish were separated into seven groups, with six experimental groups fed with EPS and EPS-ZnO NPs at 2, 5, and 10 mg/g and a control fed a basal diet. The fish ingesting feed supplemented with EPS and EPS-ZnO NPs at 10 mg/g showed improved growth performance. Cellular and humoral-immunological parameters were tested in serum and mucus after 15 and 30 days of feeding. These parameters were substantially enriched with a 10 mg/g diet (p < 0.05) of EPS and EPS-ZnO NPs in comparison with the control. Furthermore, the EPS and EPS-ZnO NP supplemental diet actively enhanced the antioxidant response (glutathione peroxidase, superoxide dismutase, and catalase). In addition, the supplemental diet of EPS and EPS-ZnO NPs lowered the death rate and improved the disease resistance of O. mossambicus following assessment with A. hydrophila and V. parahaemolyticus at 50 µL. Hence, the overall results suggest that the supplemental diet of EPS and EPS-ZnO NPs might be used to ensure aquaculture feed additives.

Efficacy of recombinant subunit OMP and hly vaccines against Aeromonas hydrophila in Rohu (Labeo rohita)

The main aim of the current study was to clone and express a new outer membrane protein (OMP) and haemolysin (hly) from a pathogenic Aeromonas hydrophila and to investigate their potential as a vaccine candidate against A. hydrophila infection in Rohu (Labeo rohita). The OMP and hly genes were cloned in pET-30b vector and recombinant plasmids pET-30b-OMP and pET-30b-hly were constructed, which were then transferred into Escherichia coli BL21 (DE3). The recombinant E. coli BL21 (DE3) was induced by IPTG, and the OMP and hly proteins were expressed highly. The proteins OMP and hly were estimated in 15% SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Their molecular weights were found to be 40 kD and 68 kD. The expressed proteins OMP and hly were purified by Ni-NTA His-Bind Resin column, and the immunogenicity was confirmed by Western blotting. The fishes (L. rohita) were divided into IV groups, and the group I fishes were treated with phosphate saline, the II and III group were immunized with the purified OMP and hly recombinant proteins, and the fishes were treated IV group with combined OMP and hly for 10 days. After 10 days of treatment, the fishes of all the four groups were challenged with virulent A. hydrophila. The results revealed that vaccinated fish showed significantly improved haematological profile, phagocytic activity, myeloperoxidase activity and total immunoglobulin levels on the 5th and 10th days. The non-vaccinated group (Group I) showed 100% mortality, whereas the mixture of recombinant OMP (r-OMP) and hly (r-hly) protein-treated groups (Group IV) exhibited higher survival rate (80%). Relatively, expression of pro- and anti-inflammatory cytokines (IL-1β, IL-10 and TGF-β), c-type and g-type lysozymes were significantly up-regulated in heart and kidney of vaccinated groups compared with the non-vaccinated group. Our results revealed that OMP and hly genes were effective vaccine candidates in the aquaculture system and could be used as recombinant subunit vaccine for diseases caused by pathogenic A. hydrophila.

Effect of an Oral Bivalent Vaccine on Immune Response and Immune Gene Profiling in Vaccinated Red Tilapia (Oreochromis spp.) during Infections with Streptococcus iniae and Aeromonas hydrophila

Streptococcosis and aeromonasis inflicted by Streptococcus iniae and Aeromonas hydrophila, respectively, have affected tilapia industries worldwide. In this study, we investigated antibody responses and explored the mechanisms of protection rendered by an oral bivalent vaccine in red tilapia following challenges with S. iniae and A. hydrophila. The results of specific IgM antibody response revealed that the IgM titers against S. iniae and A. hydrophila in the bivalent incorporated (BI) vaccine group were significantly higher (p < 0.05) than those in the bivalent spray (BS) vaccine fish and unvaccinated control fish throughout the experiment. Real-time qPCR results also showed that the gene expression of CD4, MHC-I, MHC-II, IgT, C-type lysozyme, IL-1β, TNF-α, and TGF-β remained significantly higher (p < 0.05) than that of the controls between 24 and 72 h post-infection (hpi) in both mucosal (hindgut) and systemic (spleen and head−kidney) organs of BI vaccinated fish. Furthermore, the highest relative expression of the TGF-β, C-type lysozyme, and IgT genes in the BI vaccinated group was observed in the challenged fish’s spleen (8.8-fold), head kidney (4.4-fold), and hindgut (19.7-fold) tissues, respectively. The present study suggests that the bivalent incorporated (BI) vaccine could effectively improve the immune function and activate both humoral and cell-mediated immunities in vaccinated red tilapia following the bacterial challenges.

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.

In vitro bacterial probiotic selection from Nannostomus beckfordi, an Amazon ornamental fish

ABSTRACT This study aimed to isolate and select in vitro bacteria with probiotic potential for the Amazon ornamental fish Nannostomus beckfordi. For isolate, twelve fish underwent surgery procedure to remove their intestinal tract, macerate and then inoculate in the plate petri containing de Man Rugosa Sharped Agar (MRS). After bacterial growth (48 hours at 35ºC), selected strains were inoculated in MRS broth and submitted to resistance test with NaCl (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0%), pH (4, 5, 6, 8 and 9) and bile salts (5% w/v). Inhibition test against pathogenic bacteria Aeromonas hydrophila, Pseudomonas aeroginosa, Streptococcus agalactiae and Aeromonas Jandaei was also performed. Within the isolated strains group (23 strains), only six (S1, S2, S3, S4, S5 and S6) showed probiotic potential. Strains S1 and S6 showed the greater resistance for NaCl (0.5% and 1%) and pH (5 and 6), but only S1 obtained better results to resist the bile salts. Even against pathogenic bacteria, the S1 showed the best results with inhibition halos greater than 9 mm. In the end, this bacterial strain (S1) was identified as Enterococcus faecium 11037CHB. Thus, this is the first report regarding isolated autochthonous bacterium E. faecium with probiotic potential of N. beckfordi.

Oral delivery of pVAX-OMP and pVAX-hly DNA vaccine using chitosan-tripolyphosphate (Cs-TPP) nanoparticles in Rohu, (Labeo rohita) for protection against Aeromonas hydrophila infection

The present study examines the effectiveness of DNA vaccine against Aeromonas hydrophila through oral route using chitosan-tripolyphosphate (Cs-TPP) nanoparticles encapsulation. The virulent gene of outer membrane protein (OMP) and hemolysin (hly) related to pathogenicity of A. hydrophila was used to construct a DNA vaccine using pVAX1, and the construct was named as pVAX-OMP and pVAX-hly DNA vaccines. The pVAX-OMP and pVAX-hly DNA vaccines were encapsulated by Cs-TPP nanoparticles and size measured by field emission scanning electron microscopy (FE-SEM). The encapsulation efficiency of Cs-TPP nanoparticles was found to be 79.6% for pVAX-OMP DNA and 82.3% for pVAX-hly DNA binding with Cs-TPP nanoparticles. The stability and invitro release profile of plasmid DNA was also determined after encapsulation using DNase and chitosanase. DNA vaccines distribution in tissues was investigated in fish fed with the pVAX-OMP, pVAX-hly and pVAX-OMP+pVAX-hly encapsulated in Cs-TPP nanoparticles and confirmed by PCR and multiplex PCR. The results suggest that Cs-TPP nanoparticles encapsulated DNA vaccine delivered into fish by feeding. After oral vaccination of Labeo rohita were challenged with A. hydrophila by intraperitoneal injection. Relatively, gene expression of c- and g-type lysozyme followed by pro- and anti-inflammatory cytokines (Interlukin-10 and Tumor Growth Factor β) was up-regulated in heart and kidney for pVAX-OMP+pVAX-hly vaccinated group. Moreover, fish fed with pVAX-OMP+pVAX-hly encapsulated in Cs-TPP nanoparticles had a significantly higher survival rate (76.2%) against A. hydrophila. This study concludes that pVAX-OMP and pVAX-hly DNA vaccines can be delivered orally using Cs-TPP nanoparticles for protection against A. hydrophilainfection.

Specific bioactivity of IL-22 in intestinal cells as revealed by the expression of IL-22RA1 in Mandarin fish, Siniperca chuatsi

IL-22, a multifunctional cytokine, acts as an important regulator in host immunity in mammals. IL-22 homologues have been characterized in several species of fish, with its expression found in multiple tissues/cells in fish, but its target cells have not been fully analyzed. In the present research, different organ/tissue isolated cells were examined for the expression of IL-22 and the induced IL-22 responses in mandarin fish. The mandarin fish IL-22 was found to be expressed in all these tested cells with high basal expression in intestinal cells. The HKLs showed low basal expression but significant increase in expression of IL-22 after LPS treatment or bacterial infection. Only intestinal cells showed response to IL-22 by enhanced expression of hepcidin, LEAP2 and IL-22BP, with unresponsiveness observed in other tested cells, which indicated the cell-specificity of IL-22 bioactivity in mandarin fish. One of the heterodimeric receptor components for IL-22, the IL-22RA1, was cloned in mandarin fish, with four tandem fibronectin type III (FNIII) domains identified in its extracellular part. IL-22RA1 exhibited an intestinal cell-specific expression pattern, although another receptor component of IL-22, IL-10R2, displayed constitutive expressions in all these tested cells. The present study reveals that the mandarin fish IL-22 exhibits its bioactivity in a cell-specific manner in intestinal cells, which is reflected in the restrictive expression of its receptor unit, IL-22RA1.

Effects of Lactobacillus rhamnosus ATCC 7469 on Different Parameters Related to Health Status of Rainbow Trout (Oncorhynchus mykiss) and the Protection Against Yersinia ruckeri

In the current study, we investigated the effect of a probiotic bacterium (Lactobacillus rhamnosus ATCC 7469) microencapsulated with alginate and hi-maize starch and coated with chitosan on improving growth factors, body composition, blood chemistry, and the immune response of rainbow trout (initial weight: 18.41 ± 0.32 g). Four experimental diets were formulated to feed fish for 60 days. They were control diet without any additive (C), diet added with beads without probiotic (E), a probiotic sprayed to the diet (L.r), and encapsulated probiotic supplemented diet (E-L.r). The results indicated that feeding with E-Lr significantly improved weight gain (84.98 g) and feed conversion ratio (0.95) compared to the other groups (P < 0.05). Also, fish fed E-Lr diet had a significantly higher value of whole-body protein (17.51%), total protein in the blood (4.98 g/dL), lysozyme (30.66 U/mL), alternative complement pathway hemolytic activity (134 U/mL), superoxide dismutase (203 U/mg protein), and catalase (528.33 U/mg protein) (P < 0.05) as compared to those fed the control diet. Similarly, a higher relative expression of immune-related genes such as interleukin-1 (Il-1) and tumor necrosis factor-alpha (TNF-1α) were reported in those fed E-L.r and L.r diets respectively. Interestingly, the fish fed dietary E-L.r had a significantly lower value of lipid in the whole body (4.82%) and cholesterol in the blood (160.67%) in comparison with those fed the control diet (P < 0.05). At the end of the experiment, all groups were challenged by Yersinia ruckeri where the survival rate of rainbow trout fed dietary E-L.r (70.36%) was statistically higher than that of the others (P < 0.05). Overall, the results suggested that encapsulated probiotic Lact. rhamnosus ATCC 7469 acted better than unencapsulated probiotic and has a potential to improve growth performance, flesh quality, and the immune response of rainbow trout.

Dietary Administration of Probiotic Aeromonas veronii V03 on the Modulation of Innate Immunity, Expression of Immune-Related Genes and Disease Resistance Against Aeromonas hydrophila Infection in Common Carp (Cyprinus carpio)

This study investigates the effects of dietary Aeromonas veronii V03 supplementation on growth performances, innate immunity, and expression of immune-related genes in lymphoid organs of Cyprinus carpio and resistance to Aeromonas hydrophila infection. Fish were fed for 4 weeks with basal diet (BD; without probiotic), and experiment diet containing different doses of A. veronii V03 at 3.2 × 10⁷ (DI) and 3.5 × 10⁹ (DII) CFU g^-1 of diet. At the end of the probiotic feeding trial, fish were challenged with A. hydrophila, and the percentage of survival rates was recorded over 7 days. Results revealed that fish fed with A. veronii V03 demonstrated a significant improvement in growth and enhancement of innate immunity, including respiratory burst, myeloperoxidase, and lysozyme activities, and total immunoglobulin level compared with BD fed to fish. Relatively, expression of cytokines (MyD88, IL-1β1, IL-8, and IL-10) and c- and g-type lysozymes were significantly up- and downregulated in lymphoid organs of fish. Moreover, dietary supplementation of A. veronii V03 exhibited significantly (p < 0.001) higher survival rates of DI (90%) and DII (96.66%) compared with BD (53.33%) fed fish against A. hydrophila infection. These findings help to understand the effects of probiotic A. veronii V03 administrated feed influences on growth and ailment resistance to A. hydrophila infection by regulating innate and systemic immunity in common carp fish.

Patterns of the innate immune response in tambaqui Colossoma macropomum: Modulation of gene expression in haemorrhagic septicaemia caused by Aeromonas hydrophila

The production of tambaqui Colossoma macropomum has recently reached a milestone, being considered the main native species produced in South American continental waters. Despite the importance of this fish, its immunity is not well understood. In this study we established some patterns of innate immunity for the species via two experiments. Both studies evaluated the fish in the absence (intraperitoneal saline) or presence (intraperitoneal, 3 x 10⁷ CFU/mL of Aeromonas hydrophila at 0.1 mL/10 g of living weight) of infection at 5 points over time-course of 14 days (0 h, 6 h, 24 h, 7 d, 14 d). In the first experiment, the partial gene sequences and gene expression of IL-1β, IRAK-1, C3, C4, lysozyme, IL-10, HSP70 and β-actin were determined in the main secondary lymphoid organs of fish: the spleen and head kidney. The second study was performed to analyse the alternative complement pathway ACH₅₀ in serum to support the elucidation of C3 gene expression. Results of the gene expression assays showed a tendency towards up-regulation of immune genes in infected fish in early phases of infection (mostly around 6 h and 24 h) and in the chronic phase (7 d and 14 d), with the exception of HSP70 which showed a down-regulation in infected fish. Our results also suggested that lysozyme was evolved in both pro- and anti-inflammatory activities. For genes of the complement system, it was demonstrated that C4 regulation followed the tendency of pro-inflammatory genes. However, the C3 gene was, surprisingly, not expressed in most fish and this corroborated with the results of the complement system activity in serum that also did not show activity in most fish. The possible reasons for the regulation of gene expression and association with fish disease are addressed in this paper.

Hydrolytic Exoenzymes Produced by Bacteria Isolated and Identified From the Gastrointestinal Tract of Bombay Duck

Bacteria producing hydrolytic exoenzymes are of great importance considering their contribution to the host metabolism as well as for their various applications in industrial bioprocesses. In this work hydrolytic capacity of bacteria isolated from the gastrointestinal tract of Bombay duck (Harpadon nehereus) was analyzed and the enzyme-producing bacteria were genetically characterized. A total of twenty gut-associated bacteria, classified into seventeen different species, were isolated and screened for the production of protease, lipase, pectinase, cellulase and amylase enzymes. It was found that thirteen of the isolates could produce at least one of these hydrolytic enzymes among which protease was the most common enzyme detected in ten isolates; lipase in nine, pectinase in four, and cellulase and amylase in one isolate each. This enzymatic array strongly correlated to the previously reported eating behavior of Bombay duck. 16S rRNA gene sequence-based taxonomic classification of the enzyme-producing isolates revealed that the thirteen isolates were grouped into three different classes of bacteria consisting of eight different genera. Staphylococcus, representing ∼46% of the isolates, was the most dominant genus. Measurement of enzyme-production via agar diffusion technique revealed that one of the isolates which belonged to the genus Exiguobacterium, secreted the highest amount of lipolytic and pectinolytic enzymes, whereas a Staphylococcus species produced highest proteolytic activity. The Exiguobacterium sp. expressing a maximum of four hydrolases, appeared to be the most promising isolate of all.

Induction of mitochondria-mediated apoptosis and suppression of tumor growth in zebrafish xenograft model by cyclic dipeptides identified from Exiguobacterium acetylicum

Colorectal cancer is the most common type of gastrointestinal cancers with poor survival and limited therapeutic options. In this study, four structurally different cyclic dipeptides (or diketopiperazine) were isolated and identified as cyclo (l-Pro-l-Leu), cyclo (l-Pro-l-Val), cyclo (l-Pro-l-Phe) and cyclo (l-Pro-l-Tyr) from the ethyl acetate extract in the cell-free filtrate of Exiguobacterium acetylicum S01. The anticancer potential of identified DKPs on colorectal cancer HT-29 cells in vitro and in vivo zebrafish xenograft model was evaluated. The MTT (3-(4, 5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide)) assay showed that four DKPs exhibited significant inhibition of HT-29 cells viability in a dose-dependent manner whereas there were no cytotoxic effects on normal mouse fibroblast 3T3 cells. Also, we observed that all DKPs induce early and late apoptotic cell death in HT-29 cells. Moreover, the expression levels of apoptotic (cytochrome-c, caspase-3 and Bid) and anti-apoptotic (Bcl-2) markers were up- and down-regulated in HT-29 cells in response to DKPs treatments. Furthermore, these four DKPs remarkably inhibited the tumor progression in a zebrafish xenograft model within a nonlethal dose range. Overall, our findings suggest that cyclic dipeptides derived from E. acetylicum S01 could be promising chemopreventive/ therapeutic candidates against cancer.

Synergistic Effects of Selenium Nanoparticles and Vitamin E on Growth, Immune-Related Gene Expression, and Regulation of Antioxidant Status of Nile Tilapia (Oreochromis niloticus)

The present study was conducted to investigate the effects of nano-selenium (Nano Se) or/and vitamin E (VE) on growth performance, blood health, intestinal histomorphology, oxidative status, and immune-related gene expression of Nile tilapia. Nano Se or/and VE at a rate of 0, 1 mg Nano Se/kg, 100 mg VE/kg, and 1 mg Nano Se/kg + 100 mg VE diet were fed to fish for 8 weeks. FBW was significantly (P < 0.05) increased in fish fed with Nano Se and VE, while fish fed with Nano Se or Nano Se and VE diets displayed significantly (P < 0.05) higher WG and SGR than the other groups. The lowest FCR was significantly (P < 0.05) detected in fish fed with Nano Se and VE, while the highest value was observed in fish VE diet. The intestinal morphometry (villi length and width) of fish fed with Nano Se or/and VE reported significantly (P < 0.05) the highest values with high number of goblet cells. Blood hematology and biochemistry parameters of fish fed with Nano Se or/and VE showed normal values with insignificant differences except for the blood total protein increased in fish fed with Nano Se or/and VE (P < 0.05). Dietary Nano Se or Nano Se and VE significantly (P < 0.05) increased the GPX, SOD, CAT, NBT, lysozyme, and phagocytosis values with decreased MDA. Liver and spleen TNF-α and IL-1β expressions were significantly (P < 0.05) upregulated in fish fed on Nano Se or Nano Se and VE. Thus, Nano Se or/and VE can be used effectively in tilapia diets for improving the growth, intestinal health, blood health, oxidative status, and immune-related gene expression.

Dietary supplementation of Geotrichum candidum improves growth, gut microbiota, immune-related gene expression and disease resistance in gibel carp CAS Ⅲ (Carassius auratus gibelio)

Geotrichum candidum is a filamentous fungus mostly used in the dairy industry for cheese ripening and flavoring. The current study was designed to evaluate the potential probiotics effect of dietary supplementation of G. candidum on growth, digestive enzymes activities, gut microbiota and immune-related gene expression and disease resistance in Gibel carp CAS Ⅲ (Carassius auratus gibelio) against A. hydrophila infections. For this purpose, 420 healthy fish (initial body weight: 7.09 ± 0.02g) were randomly divided into 7 feeding groups in triplicates of 20 fish in each tank. Seven isocaloric and isonitrogenous diets were prepared, supplemented with 6 different doses of G. candidum viz; C: 0, T1:10⁶, T2:10⁷, T3:10⁸, T4:10⁹, T5:10¹⁰, T6:10¹¹ CFU/kg diet and fed to fish twice a day for 60 days. Results showed significantly higher weight gain (WG) and feed efficiency (FE) in groups fed 10⁶ and 10⁸ CFU/kg diet compared to the control (P < 0.05). All G. candidum fed groups showed higher intestinal α-amylase activity (P < 0.05) while no difference in lipase and trypsin activity compared to the control group. Before challenge test, gut microbial diversity analysis revealed relatively more abundance of bacteria belonging to phylum Proteobacteria, Actinobacteria, Firmicutes and Bacteriodetes in group fed G. candidum supplemented diet and higher percentage of pathogenic bacteria belonging to order Aeromonadales and Vibrionales in control post-challenge. After challenge test immune response expressed numerically higher survival rate (P > 0.05) and significantly higher (P < 0.05) Respiratory Burst Activity(RBA), Immunoglobulin M level (IgM), Aspartate Transaminase activity (AST) and improved (P > 0.05) lysozyme activity, and Alanine Transaminase activity (ALT) in groups fed 10⁶ and 10⁸ CFU/kg G. candidum supplemented diet. The expression of immune related gene (IL-I β, TNF- α, HSP70 and TLR-2) in liver of the fish were significantly affected (P < 0.05) by supplementation of G. candidum post bacterial challenge. The results showed that G. candidum is a potential probiotic as it could improve feed utilization, immunity and cause no harmful effects on growth of gibel carp at higher supplementation levels. The productive results can be achieved by using the lower dose as 10⁶-10⁸ CFU/kg diet.

Effects of thymol supplementation on performance, mortality and branchial energetic metabolism in grass carp experimentally infected by Aeromonas hydrophila

We determined whether thymol supplementation of would minimize the negative effects of Aeromonas hydrophila infection on branchial energy metabolism, weight loss and mortality in grass carp (Ctenopharyngodon idella). We found that the infected fish all died, while 62.5% of those supplemented with 100 mg/kg thymol survived. Cytosolic and mitochondrial creatine kinase (CK) activities, as well as adenylate kinase (AK) and pyruvate kinase (PK) activities were significant lower in gills of A. hydrophila-infected fish than those of the control group, and adenosine triphosphate (ATP) levels were significant lower in the infected group. Finally, branchial reactive oxygen species (ROS) were significant higher in A. hydrophila-infected fish than in the control group. Supplementation with 100 and 300 mg thymol/kg diet prevented inhibition of branchial cytosolic and mitochondrial CK activities caused by infection, and also inhibited the reduction of branchial ATP levels. Supplementation with 100, 200 and 300 mg thymol/kg prevented the inhibition of branchial AK and PK activities induced by aeromonosis. Supplementation of 100 mg thymol/kg prevented weight loss after A. hydrophila infection. These data suggest that supplementation with 100 mg thymol/kg exerts potent bactericidal properties and augments longevity. Supplementation at all concentrations of thymol prevented A. hydrophila-induced branchial bioenergetics; nevertheless, higher concentrations were associated with side-effects.

Effect of Lactobacillus casei on Innate Immunity Responses and Aeromonas hydrophila Resistance in Shabot, Tor grypus

For investigating the possible effect of Lactobacillus casei on the immune status of Shabot, Tor grypus, 480 fish weighing 40 ± 10 g were randomly divided into four groups in triplicate. The first group (control) was fed on a commercial diet without probiotic supplementation. Other groups (A, B, and C) were received diet supplemented by different levels of L. casei, i.e., 5 × 10⁶, 5 × 10⁷, and 5 × 10⁸ CFU g^-1, respectively. The feeding trial was performed for 60 continuous days followed by 15 days as withdraw period, i.e., day 75. Serum immune responses were determined on days 0, 30, 60, and 75 of feeding trial. Gene expression in the kidneys was analyzed on days 0, 60, and 75 as well as following bacterial challenge. The results showed that dietary L. casei supplementation significantly (P < 0.05) increased serum lysozyme, serum bactericidal, complement, and respiratory burst activities as compared with control group, while it was observed that treated fish did not show any significant differences in immune responses on day 75 (P < 0.05). Results of gene expression (TNF-α, IL-1β, and IL-8) showed significant increases among different experimental times (P < 0.05). According to obtained results, it might be concluded that the feeding by L. casei could likely enhance the immune responses and gene expression in T. grypus. Treatments A and C were better than B, but the lower concentration is better as an economic viewpoints and biosecurity. Therefore, concentration A is suggested.