Effects of various feeding patterns of Bacillus coagulans on growth performance, antioxidant response and Nrf2-Keap1 signaling pathway in juvenile gibel carp (Carassius auratus gibelio)

Effects of Dietary β-Glucan Feeding Strategy on the Growth, Physiological Response, and Gut Microbiota of Pacific White Shrimp, Litopenaeus vannamei, under Low Salinity

An eight-week feeding trial was conducted to investigate the effects of a dietary β-glucan application strategy on the growth performance, physiological response, and gut microbiota of Pacific white shrimp (Litopenaeus vannamei) (0.49 ± 0.17 g) under low salinity. Six feeding strategies were established, including a continuous β-glucan-free diet group (control), a continuously fed group with a 0.1% β-glucan diet (T1), and groups with the following intermittent feeding patterns: 1 day of β-glucan diet and 6 days of β-glucan-free diet (T2), 2 days of β-glucan diet and 5 days of β-glucan-free diet (T3), 3 days of β-glucan diet and 4 days of β-glucan-free diet (T4), and 4 days of β-glucan diet and 3 days of β-glucan-free diet (T5) each week. No significant differences in growth performance among all the groups were found, although the condition factor was significantly higher in the T3 group than in the T1 and T5 groups (p < 0.05). The T-AOC and GPX activities were significantly lower in the T3 group than in the control group (p < 0.05). The MDA content was also significantly lower in the T2 group than in the T3 and T4 groups (p < 0.05). Additionally, the mRNA expression of the Pen3a gene was significantly upregulated in the hepatopancreas of the T4 group compared to the control and T5 groups (p < 0.05), and the Toll gene was also significantly upregulated in the T3 group compared to the T1 and T2 groups (p < 0.05). Dietary β-glucan induced changes in the alpha diversity and composition of the gut microbiota in different feeding strategies. The beta diversity of the gut microbiota in the T2 group was significantly different from that in the control group. The results of a KEGG analysis showed that gut function in the carbohydrate metabolism, immune system, and environmental adaptation pathways was significantly enhanced in the T3 group. These findings provide evidence that the intermittent feeding strategy of β-glucan could alleviate immune fatigue, impact antioxidant ability, and change gut microbiota composition of L. vannamei under low salinity.

Effects of Dietary Bacillus coagulans and Tributyrin on Growth Performance, Serum Antioxidants, Intestinal Morphology, and Cecal Microbiota of Growing Yellow-Feathered Broilers

This study investigated the impact of Bacillus coagulans (BC) and tributyrin (TB) supplementation on the growth performance, serum antioxidant capacity, intestinal morphology, and cecal microbiota of yellow-feathered broilers. Using a 2 × 2 factorial design, 480 broilers were randomly assigned to four experimental diets, comprising two levels of BC (0 and 1 g/kg) and two levels of TB (0 and 1 g/kg), over a 36-day period. A significant interaction was observed between BC and TB, impacting the average daily feed intake (ADFI) of broilers aged between 26 and 40 days (p < 0.01). BC and TB also displayed a significant interaction in relation to serum malondialdehyde levels and total antioxidant capacity (p < 0.05). Additionally, there was a significant interaction between BC and TB concerning the duodenal villus-to-crypt ratio, crypt depth, and jejunal villus-to-crypt ratio (p < 0.05). The addition of BC and TB significantly enhanced the richness and diversity of cecal microbiota, with a notable interactive effect observed for the abundance of Faecalibacterium, Ruminococcus_torques_group, and Phascolarctobacterium. In conclusion, supplementation with BC and TB can effectively improve the growth performance, serum antioxidant capacity, intestinal morphology, and cecal microbiota composition of yellow-feathered broilers, indicating the presence of an interactive effect.

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.

Evaluation of dietary single probiotic isolates and probiotic multistrain consortia in growth performance, gut histology, gut microbiota, immune regulation, and infection resistance of Nile tilapia, Oreochromis niloticus, shows superior monostrain performance

The probiotic potential of a designed bacterial consortia isolated from a competitive exclusion culture originally obtained from the intestinal contents of tilapia juveniles were evaluated on Nile tilapia alevins. The growth performance, intestinal histology, microbiota effects, resistance to Streptococcus agalactiae challenge, and immune response were assessed. In addition, the following treatments were included in a commercial feed: A12+M4+M10 (Lactococcus lactis A12, Priestia megaterium M4, and Priestia sp. M10), M4+M10 (P. megaterium M4, and Priestia sp. M10) and the single bacteria as controls; A12 (L. lactis A12), M4 (P. megaterium M4), M10 (Priestia sp. M10), also a commercial feed without any probiotic addition was included as a control. The results showed that all probiotic treatments improved the growth performance, intestinal histology, and resistance during experimental infection with S. agalactiae in comparison to the control fish. Also, the administration of probiotics resulted in the modulation of genes associated with the innate and adaptive immune systems that were non-dependent on microbial colonization. Surprisingly, L. lactis A12 alone induced benefits in fish compared to the microbial consortia, showing the highest increase in growth rate, survival during experimental infection with S. agalactiae, increased intestinal fold length, and the number of differentially expressed genes. Lastly, we conclude that a competitive exclusion culture is a reliable source of probiotics, and monostrain L. lactis A12 has comparable or even greater probiotic potential than the bacterial consortia.

Weizmannia coagulans JA845 improves atherosclerosis induced by vitamin D3 and high-fat diet in rats through modulating lipid metabolism, oxidative stress, and endothelial vascular injury

AIMS

Probiotics have been proved to be strongly linked to the occurrence and progression of atherosclerosis. This study aimed to investigate the improved effects and mechanisms underlying a potential probiotic, Weizmannia coagulans JA845, on atherosclerosis.

METHODS AND RESULTS

Male Sprague-Dawley rats supported on a high-fat diet with vitamin D3 supplementation were subjected to W. coagulans JA845 treatment. W. coagulans JA845 obviously alleviated histological abnormalities of the abdominal aorta. After 6 weeks of W. coagulans JA845 administration, levels of TG, TC, LDL, ox-LDL, ROS, and MDA in the JA845 group decreased significantly, and those of HDL, GSH-Px, and SOD were markedly elevated. Treatment with W. coagulans JA845 also inhibited the secretion of ICAM-1 and VCAM-1 and regulated the plasma NO and eNOS content. In brief, administration of W. coagulans JA845 promoted the expression of the SIRT3/SOD2/FOXO3A pathway, inhibited the lipid metabolism pathway, SREBP-1c/FAS/DGAT2, and suppressed the JNK2/P38 MAPK/VEGF pathway implicated in endothelial injury.

CONCLUSIONS

These results indicated W. coagulans JA845 improved atherosclerosis by regulating lipid metabolism, antioxidative stress, and protecting against endothelial injury.

Effects of Bacillus spp. Mixture on Growth, Immune Responses, Expression of Immune-Related Genes, and Resistance of Nile Tilapia Against Streptococcus agalactiae Infection

The purpose of this study was to evaluate the effect of Bacillus spp. mixture (Bacillus subtilis TISTR001, Bacillus megaterium TISTR067, and Bacillus licheniformis DF001) (1 × 10⁶ CFU/g) on growth, immune parameters, immune-related gene expression, and resistance of Nile tilapia against Streptococcus agalactiae AAHM04. Fish were fed different concentrations of Bacillus spp. 0 (control; T1), 1 (T2), 3 (T3), and 5 (T4) g/kg diets for 120 days. The results showed that weight gain, average daily gain, specific growth rate, feed conversion ratio in T3 diet were significantly higher than the control group and other tested diets (p < 0.05). Immune parameters, such as myeloperoxidase and lysozyme, were significantly higher in the T3 and T4 diets compared to the control group (p < 0.05). Similarly, IL-1β and TNF-α gene expressions in the spleen of fish fed T2, T3, and T4 diets were significantly higher than the control group (p < 0.05). However, no significant differences in survival rate, hematology, blood chemical indices, malondialdehyde (MDA) levels, body chemical composition, and organosomatic indices (p > 0.05) were noticed in all treatments. No significant differences in survival rate after the challenge test with S. agalactiae AAHM04 were found in fish fed Bacillus spp. mixture diets, except for the T3 diet. These results suggest that Bacillus spp. mixture diet at 3 g/kg diet (T3) could improve growth, immune response, and disease resistance of Nile tilapia.

Probiotics ameliorate growth retardation of glyphosate by regulating intestinal microbiota and metabolites in crucian carp (Carassius auratus)

Glyphosate (GLY) contamination widely occurred in aquatic environments including aquaculture systems and raised hazard to aquatic organisms such as fish. Probiotics have been reported to alleviate contaminants-induced toxicity. However, whether probiotics could reduce the health risk of GLY to fish remain unknown. Here we investigated the impacts of GLY on crucian carp (Carassius auratus) by focusing on the protective roles of two commonly used aquaculture probiotics, Bacillus coagulans (BC) and Clostridium butyricum (CB). Exposure to GLY significantly caused growth retardation and reduced visceral fat and intestinal lipase activity in crucian carp. 16S rRNA sequencing indicated that dysbiosis of Bacteroidetes at phylum level and Flavobacterium at genus level might be primarily responsible for GLY-induced negative growth performance. High throughput targeted quantification for metabolites revealed that GLY changed intestinal metabolites profiles, especially the reduced bile acids and short-chain fatty acids. However, the addition of BC or CB effectively attenuated the adverse effects above by remodeling the gut microbiota composition and improving microbial metabolism. The present study provides novel evidence for ameliorating the harmful effects of GLY on fish species by adding probiotics, which highlights the potential application of probiotics in reducing the health risks of GLY in aquatic environment.

Application of Weizmannia coagulans in the medical and livestock industry

Purpose

Products enriched with probiotics have always been fashionable. Weizmannia coagulans has become a hot research topic in the academic community due to their multiple functional properties and high resistance to stress, which can retain their activity in a variety of harsh environments. This review aims to evaluate the probiotic effects of different strains of Weizmannia coagulans in animals and humans and to inspire better exploitation of the value of this strain.

Methods

This review summarizes the latest research progress of Weizmannia coagulans from two major applications in animal breeding and human health.

Results

The functional properties of Weizmannia coagulans are extensively recognized. In animals, the strain can promote nutrient absorption, reduce mortality, and enhance the slaughter rate in livestock and poultry. In humans, the strain can be used to treat gastrointestinal disorders, immunomodulation, depressive symptoms, and non-alcoholic fatty liver. Weizmannia coagulans is projected as an ideal substitute for antibiotics and other chemical drugs.

Conclusion

Despite the outstanding functional properties of Weizmannia coagulans, there are numerous strains of Weizmannia coagulans and significant differences between strains in functional and physiological properties. Currently, there are few literature reports on the probiotic mechanism and functional gene identification of Weizmannia coagulans, which is crucial for the commercialization of Weizmannia coagulans and the benefit of human society.

Effect of dietary Bacillus coagulans on the performance and intestinal microbiota of weaned piglets

The performance of weaned piglets suffers from severe limitations resulting from diarrhoea. Therefore, this trial was performed to investigate the effects of Bacillus coagulans as an alternative to antibiotics on piglet growth performance and intestinal health. Ninety (initial BW = 7.70 ± 0.17 kg, weaning age of 26 days) healthy weaned piglets with similar BWs were selected and randomised into three treatment groups. Pigs in the negative control (NC) group were fed a basal diet, pigs in the positive control (PC) group were fed the basal diet plus antibiotics, and pigs in the test group (BC) were fed the basal diet plus Bacillus coagulans at 600 g/t; the trial lasted for 28 days. The results showed that the ratios of feed to gain (F:G) of both the BC and PC groups from 1 to 21 days were significantly lower (P < 0.05), and the average daily weight gain (ADG) of the BC group from 22 to 28 days was significantly higher (P < 0.05) than that of the NC group in terms of growth performance. The diarrhoea index was lowest in the PC group, followed by the BC group, and highest in the NC group. The BC group had a lower diarrhoea index at the later stage. We performed 16S rRNA sequencing to measure the intestinal bacteria and found that the BC group had a higher intestinal bacteria diversity than the NC and PC groups (P < 0.05). From days 1 to 21, the main differential species were Ruminococcaceae_UCG-014 and Faecalibacterium (P < 0.05); from days 22 to 28, the main differential species were Prevotella_9, unclassified_f__Lachnospiraceae, Anaerovibrio, and Ruminococcaceae_UCG-002 (P < 0.05). The correlation analysis between growth performance and species revealed specific gut microorganisms responsible for variation in F:G, ADG, and diarrhoea index, such as Prevotellaceae, Clostridium_sensu_stricto_1, Ruminococcaceae, Phascolarctobacterium, and Anaerovibrio. In conclusion, Bacillus coagulans changed the microbial composition in the faeces of weaned piglets, which had positive effects on growth performance and the diarrhoea index. Therefore, our study provided new insight into the future application of Bacillus coagulans as an additive.

Neu1 deficiency increases the susceptibility of zebrafish to Edwardsiella piscicida infection via lysosomal dysfunction

Neu1 is a lysosomal glycosidase that catalyzes the removal of sialic acids from glycoconjugates. Although Neu1 sialidase is highly conserved among vertebrates, the role of fish Neu1 is not fully understood because of its unique aquatic living situation. Compared to land animals, fish have a higher chance of bacterial infection, and to understand the role of fish Neu1, the susceptibility of Neu1 knockout zebrafish (Neu1-KO) was evaluated using Edwardsiella piscicida, a fish pathogen. Neu1-KO larvae showed high susceptibility to E. piscicida, despite the activation of macrophages, and presented increased lysosomal signals induced by the accumulation of Sia α2-3 linked oligosaccharides. The accumulation coincided with the signal of the macrophage marker, suggesting that the dysfunction of lysosomes in macrophages would result in a high susceptibility of Neu1-KO to E. piscicida. Chloroquine, an inhibitor of lysosomal degradation, induced high mortality of wild type zebrafish with E. piscicida infection accompanied by increased lysosomal accumulation, similar to Neu1-KO zebrafish. This study revealed that Neu1 sialidase plays a crucial role in the lysosomal degradation of macrophages with a bacterial infection.

Bacillus coagulans SCC-19 maintains intestinal health in cadmium-exposed common carp (Cyprinus carpio L.) by strengthening the gut barriers, relieving oxidative stress and modulating the intestinal microflora

Heavy metal cadmium (Cd) pollution is a serious problem affecting the sustainable development of aquaculture and the safety of aquatic foods. Research about the use of probiotics to attenuate toxic damage caused by Cd2+ in aquatic animals has received widespread attention. Bacillus coagulans (B. coagulans), a kind of probiotics commonly used in aquaculture, has been shown to adsorb Cd2+ both in vivo and vitro. Here, we aimed to determine the effects of B. coagulans on Cd2+ bioaccumulation, gut barrier function, oxidative stress and gut microbiota in common carp following Cd2+ exposure. The fish were exposure to Cd2+ at 0 and 0.5 mg/L and/or fed a B. coagulans-containing diet at 107, 108 and 109 CFU/g for 8 weeks. The results indicated that B. coagulans can maintain gut barrier function in Cd2+-exposed fish by reducing Cd2+ bioaccumulation, increasing the mRNA levels of tight junction protein genes (occludin, claudin-2 and zonula occludens-1), and decreasing the levels of diamine oxidase and D-lactic acid. In addition, B. coagulans could relieve oxidative stress in Cd2+-exposed fish by restoring the activities of glutathione peroxidase, catalase and superoxide dismutase. Moreover, Cd2+ exposure decreased the intestinal microbiota diversity and changed the intestinal microbiota compositions in common carp. However, supplementation with B. coagulans could reverse the altered intestinal microbiota diversity and composition after Cd2+ exposure, decrease the abundance of some pathogens (Shewanella and Vibrio), and increase the abundance of probiotics (Bacillus and Lactobacillus). These results indicate that B. coagulans may serve as a potential antidote for alleviating Cd2+ toxicity.

Triggers for the Nrf2/ARE Signaling Pathway and Its Nutritional Regulation: Potential Therapeutic Applications of Ulcerative Colitis

Ulcerative colitis (UC), which affects millions of people worldwide, is characterized by extensive colonic injury involving mucosal and submucosal layers of the colon. Nuclear factor E2-related factor 2 (Nrf2) plays a critical role in cellular protection against oxidant-induced stress. Antioxidant response element (ARE) is the binding site recognized by Nrf2 and leads to the expression of phase II detoxifying enzymes and antioxidant proteins. The Nrf2/ARE system is a key factor for preventing and resolving tissue injury and inflammation in disease conditions such as UC. Researchers have proposed that both Keap1-dependent and Keap1-independent cascades contribute positive effects on activation of the Nrf2/ARE pathway. In this review, we summarize the present knowledge on mechanisms controlling the activation process. We will further review nutritional compounds that can modulate activation of the Nrf2/ARE pathway and may be used as potential therapeutic application of UC. These comprehensive data will help us to better understand the Nrf2/ARE signaling pathway and promote its effective application in response to common diseases induced by oxidative stress and inflammation.

Fusobacterium Nucleatum Promotes the Development of Colorectal Cancer by Activating a Cytochrome P450/Epoxyoctadecenoic Acid Axis via TLR4/Keap1/NRF2 Signaling

Emerging research has revealed regulation of colorectal cancer metabolism by bacteria. Fusobacterium nucleatum (Fn) plays a crucial role in the development of colorectal cancer, however, whether Fn infection modifies metabolism in patients with colorectal cancer remains unknown. Here, LC-MS/MS-based lipidomics identified the upregulation of cytochrome P450 monooxygenases, primarily CYP2J2, and their mediated product 12,13-EpOME in patients with colorectal cancer tumors and mouse models, which increased the invasive and migratory ability of colorectal cancer cells in vivo and in vitro by regulating the epithelial-mesenchymal transition (EMT). Metagenomic sequencing indicated a positive correlation between increased levels of fecal Fn and serum 12,13-EpOME in patients with colorectal cancer. High levels of CYP2J2 in tumor tissues also correlated with high Fn levels and worse overall survival in patients with stage III/IV colorectal cancer. Moreover, Fn was found to activate TLR4/AKT signaling, downregulating Keap1 and increasing NRF2 to promote transcription of CYP2J2. Collectively, these data identify that Fn promotes EMT and metastasis in colorectal cancer by activating a TLR4/Keap1/NRF2 axis to increase CYP2J2 and 12,13-EpOME, which could serve as clinical biomarkers and therapeutic targets for Fn-infected patients with colorectal cancer. SIGNIFICANCE: This study uncovers a mechanism by which Fusobacterium nucleatum regulates colorectal cancer metabolism to drive metastasis, suggesting the potential biomarker and therapeutic utility of the CYP2J2/12,13-EpOME axis in Fn-infected patients.

Bacteriome Structure, Function, and Probiotics in Fish Larviculture: The Good, the Bad, and the Gaps

Aquaculture is the fastest-growing sector in food production worldwide. For decades, research on animal physiology, nutrition, and behavior established the foundations of best practices in land-based fish rearing and disease control. Current DNA sequencing, bioinformatics, and data science technologies now allow deep investigations of host-associated microbiomes in a tractable fashion. Adequate use of these technologies can illuminate microbiome dynamics and aid the engineering of microbiome-based solutions to disease prevention in an unprecedented manner. This review examines molecular studies of bacterial diversity, function, and host immunitymodulation at early stages of fish development, where microbial infections cause important economic losses. We uncover host colonization and virulence factors within a synthetic assemblage of fish pathogens using high-end comparative genomics and address the use of probiotics and paraprobiotics as applicable disease-prevention strategies in fish larval and juvenile rearing. We finally propose guidelines for future microbiome research of presumed relevance to fish larviculture.

Application of Bacillus coagulans in Animal Husbandry and Its Underlying Mechanisms

In recent decades, probiotics have attracted widespread attention and their application in healthcare and animal husbandry has been promising. Among many probiotics, Bacillus coagulans (B. coagulans) has become a key player in the field of probiotics in recent years. It has been demonstrated to be involved in regulating the balance of the intestinal microbiota, promoting metabolism and utilization of nutrients, improving immunity, and more importantly, it also has good industrial properties such as high temperature resistance, acid resistance, bile resistance, and the like. This review highlights the effects of B. coagulans in animal husbandry and its underlying mechanisms.

Isolation of food-derived bacteria inducing interleukin-22 in B cells

Recently, we found a novel function of the lactic acid bacterium Tetragenococcus halophilus derived from miso, a fermented soy paste, that induces interleukin (IL)-22 production in B cells preferentially. IL-22 plays a critical role in barrier functions in the gut and skin. We further screened other bacteria species, namely, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Weissella, Pediococcus, and Bacillus, in addition to Tetragenococcus and found that some of them possessed robust IL-22-inducible function in B cells in vitro. This process resulted in the augmented expression of activation markers CD86 and CD69 on B and T cells, respectively. However, these observations were not correlated with IL-22 production. We isolated Bacillus coagulans sc-09 from miso and determined it to be the best strain to induce robust IL-22 production in B cells. Furthermore, feeding B. coagulans sc-09 to mice augmented the barrier function of the skin regardless of gut microbiota.

RETRACTED: Effluent containing Rubrivivax gelatinosus promoting the yield, digestion system, disease resistance, mTOR and NF-kB signaling pathway, intestinal microbiota and aquaculture water quality of crucian carp

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of Editors-in-Chief and first Author. The article duplicates significant parts of a paper that had already appeared in Fish & Shellfish Immunology, Volume 93 (2019) 726-731, https://doi.org/10.1016/j.fsi.2019.06.052. One of the conditions of submission of a paper for publication is that authors declare explicitly that the paper has not been previously published and is not under consideration for publication elsewhere. As such this article represents a misuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process. The first author informed the journal that the article was published without the knowledge of the co-authors.

A review on the application of Bacillus as probiotics in aquaculture

Probiotics use in aquaculture has gained attention as microbial candidates to maintain the health and the well-being of many aquaculture animals. Among the many microbial candidates, probiotic Bacillus has sporulation capacity that makes them survive harsh environmental conditions, are non-pathogenic and non-toxic when fed to fish, and can produce antimicrobial substances making them more suitable candidates compared to other probiotics. In this review, we discussed the necessity of using the probiotic Bacillus in sustainable aquaculture as a good alternative to improve feed utilization, stress response, immune response and disease resistance, maintenance of tissue integrity, and as well improvement of water quality for sustainable aquaculture. Therefore the findings of current researches about the effects of Bacillus application to improve the culture of aquatic animals for future research and development of Bacillus application in aquaculture have been summarised.

Gut Microbiota and Energy Homeostasis in Fish

The microorganisms within the intestinal tract (termed gut microbiota) have been shown to interact with the gut-brain axis, a bidirectional communication system between the gut and the brain mediated by hormonal, immune, and neural signals. Through these interactions, the microbiota might affect behaviors, including feeding behavior, digestive/absorptive processes (e.g., by modulating intestinal motility and the intestinal barrier), metabolism, as well as the immune response, with repercussions on the energy homeostasis and health of the host. To date, research in this field has mostly focused on mammals. Studies on non-mammalian models such as fish may provide novel insights into the specific mechanisms involved in the microbiota-brain-gut axis. This review describes our current knowledge on the possible effects of microbiota on feeding, digestive processes, growth, and energy homeostasis in fish, with emphasis on the influence of brain and gut hormones, environmental factors, and inter-specific differences.

Bacillus subtilis as probiotic candidate for red sea bream: Growth performance, oxidative status, and immune response traits

The effects of dietary administration of Bacillus subtilis on the growth, digestive enzyme activity, blood chemistry, oxidative status and immune response of red sea bream (Pagrus major) were evaluated in the current study. Fish fed five different levels of B. subtilis at 0 (BS0), 1 × 10⁴ (BS1), 1 × 10⁶ (BS2), 1 × 10⁸ (BS3) and 1 × 10¹⁰ (BS4) CFU kg^-1 diet for 60 days. The obtained results showed that B. subtilis supplementation significantly improved growth performance (FBW, WG and SGR), feed utilization (FI, FCE, PER and PG) and whole-body protein content when compared to the control group (P < 0.05). Furthermore, the specific activities of amylase, protease and lipase enzymes up regulated significantly upon B. subtilis incorporation in red sea bream diets (P < 0.05). No changes have been reported on blood biochemical variables except for the plasma total protein, which increased significantly in fish fed BS3 diet when compared with the control diet (P < 0.05). Hematocrit, hemoglobin and the nitro blue tetrazolium values also reported the highest values significantly in fish fed B. subtilis, especially in case of BS3 and BS4 diets (P < 0.05). Serum bactericidal activity enhanced significantly in BS2, BS3 and BS4 groups (P < 0.05), while mucus bactericidal activity showed no significant activity among tested groups (P > 0.05). Serum lysozyme activity exhibited higher values in case of BS3 and BS4 groups than BS0 group (P < 0.05), while mucus lysozyme activity increased only in BS3 group. Also, serum peroxidase activity enhanced significantly in fish fed BS2 and BS3 diets (P < 0.05), however, no activities were observed in the collected mucus. All groups reflexed high tolerance ability against oxidative stress except for BS0 and BS1 groups. Additionally, catalase activity increased significantly in all B. subtilis fed groups when compared to BS0 group (P < 0.05). Considering the obtained results, the supplementation of B. subtilis in the diet of red sea bream at 1 × 10⁸ and 1 × 10¹⁰ CFU kg^-1 diet could improve the growth, feed utilization, health condition and immune response.