Probiotic potential of Bacillus velezensis JW: Antimicrobial activity against fish pathogenic bacteria and immune enhancement effects on Carassius auratus

Dietary Bacillus velezensis T23 fermented products supplementation improves growth, hepatopancreas and intestine health of Litopenaeus vannamei

This study aimed to elucidate the effects of dietary fermented products of Bacillus velezensis T23 on the growth, immune response and gut microbiota in Pacific white shrimp (Litopenaeus vannamei). Shrimp were fed with diets containing fermentation products of B. velezensis T23 at levels of (0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 g/kg) for 4 weeks, to assess the influence on shrimp growth. The results showed that 0.3 and 0.4 g/kg T23 supplementation improved shrimp growth and feed utilization. Based on these results we selected these three diets (Control, 0.3T23 and 0.4T23) to assess the effect on immune response and gut microbiota of shrimp. Compared with the control, the 0.3T23 and 0.4T23 groups enhanced lipase and α-amylase activities in the gut significantly. Moreover, the 0.4T23 group decreased TAG and MDA levels in hepatopancreas, ALT and AST levels of serum significantly (P < 0.05). In hepatopancreas, CAT and SOD activities were improved observably and the MDA content was reduced markedly in both T23 groups. The expressions of antimicrobial related genes, Cru and peroxinectin in the 0.3T23 group, and proPO and peroxinectin in the 0.4T23 group were up-regulated remarkably (P < 0.05). Moreover, hepatopancreas of shrimp fed with a diet amended with T23 showed a significant down-regulated expression of nf-kb and tnf-α genes, while expressions of tgf-β was considerably up-regulated. Furthermore, serum LPS and LBP contents were reduced markedly in T23 groups. Intestinal SOD and CAT were noteworthy higher in T23 groups (P < 0.05). In the intestine of shrimp fed on the diet enriched with T23 the expression of nf-κb and tnf-α exhibited markedly down-regulated, whereas hif1α was up-regulated (P < 0.05). Besides, in the intestine of shrimp grouped under T23, Cru and peroxinectin genes were markedly up-regulated (P < 0.05). Dietary 0.3 g/kg T23 also upregulated the ratio of Rhodobacteraceae to Vibrionaceae in the gut of the shrimp. Taken together, the inclusion of B. velezensis T23 in the diet of shrimp enhanced the growth and feed utilization, enhanced hepatopancreas and intestine health.

[Cu(NN1)2]ClO4, a Copper (I) Complex as an Antimicrobial Agent for the Treatment of Piscirickettsiosis in Atlantic Salmon

Piscirickettsia salmonis is the pathogen that most affects the salmon industry in Chile. Large quantities of antibiotics have been used to control it. In search of alternatives, we have developed [Cu(NN1)2]ClO4 where NN1 = 6-((quinolin-2-ylmethylene)amino)-2H-chromen-2-one. The antibacterial capacity of [Cu(NN1)2]ClO4 was determined. Subsequently, the effect of the administration of [Cu(NN1)2]ClO4 on the growth of S. salar, modulation of the immune system and the intestinal microbiota was studied. Finally, the ability to protect against a challenge with P. salmonis was evaluated. The results obtained showed that the compound has an MIC between 15 and 33.9 μg/mL in four isolates. On the other hand, the compound did not affect the growth of the fish; however, an increase in the transcript levels of IFN-γ, IL-12, IL-1β, CD4, lysozyme and perforin was observed in fish treated with 40 μg/g of fish. Furthermore, modulation of the intestinal microbiota was observed, increasing the genera of beneficial bacteria such as Lactobacillus and Bacillus as well as potential pathogens such as Vibrio and Piscirickettsia. Finally, the treatment increased survival in fish challenged with P. salmonis by more than 60%. These results demonstrate that the compound is capable of protecting fish against P. salmonis, probably by modulating the immune system and the composition of the intestinal microbiota.

Biocontrol manufacturing and agricultural applications of Bacillus velezensis

Many microorganisms have been reported as bioagents for producing ecofriendly, cost-effective, and safe products. Some Bacillus species of bacteria can be used in agricultural applications. Bacillus velezensis in particular has shown promising results for controlling destructive phytopathogens and in biofungicide manufacturing. Some B. velezensis strains can promote plant growth and display antibiotic activities against plant pathogen agents. In this review, we focus on the often-overlooked potential properties of B. velezensis as a bioagent for applications that will extend beyond the traditional agricultural uses. We delve into its versatility and future prospects, the challenges such uses may encounter, and some drawbacks associated with B. velezensis-based products.

Analysis of antimicrobial biological activity of a marine Bacillus velezensis NDB

A new strain of Bacillus velezensis NDB was isolated from Xiangshan Harbor and antibacterial test revealed antibacterial activity of this strain against 12 major pathogenic bacteria. The whole genome of the bacterium was sequenced and found to consist of a 4,214,838 bp circular chromosome and a 7410 bp circular plasmid. Furthermore, it was predicted by AntiSMASH and BAGEL4 to have 12 clusters of secondary metabolism genes for the synthesis of the inhibitors, fengycin, bacillomycin, macrolactin H, bacillaene, and difficidin, and there were also five clusters encoding potentially novel antimicrobial substances, as well as three bacteriocin biosynthesis gene clusters of amylocyclicin, ComX1, and LCI. qRT-PCR revealed significant up-regulation of antimicrobial secondary metabolite synthesis genes after 24 h of antagonism with pathogenic bacteria. Furthermore, MALDI-TOF mass spectrometry revealed that it can secrete surfactin non-ribosomal peptide synthase and polyketide synthase to exert antibacterial effects. GC-MS was used to analyze methanol extract of B. velezensis NDB, a total of 68 compounds were identified and these metabolites include 16 amino acids, 17 acids, 3 amines, 11 sugars, 11 alcohols, 1 ester, and 9 other compounds which can inhibit pathogenic bacteria by initiating the antibiotic secretion pathway. A comparative genomic analysis of gene families showed that the specificity of B. velezensis NDB was mainly reflected in environmental adaptability. Overall, this research on B. velezensis NDB provides the basis for elucidating its biocontrol effect and promotes its future application as a probiotic.

Targeted Screening of Fiber Degrading Bacteria with Probiotic Function in Herbivore Feces

Cellulolytic bacteria with probiotic functions play a crucial role in promoting the intestinal health in herbivores. In this study, we aimed to correlate the 16S rRNA gene amplicon sequencing and fiber-degrading enzyme activity data from six different herbivore feces samples. By utilizing the separation and screening steps of probiotics, we targeted and screened high-efficiency fiber-degrading bacteria with probiotic functions. The animals included Maiwa Yak (MY), Holstein cow (CC), Tibetan sheep (TS), Southern Sichuan black goat (SG), Sichuan white rex rabbit (CR), and New Zealand white rabbit (ZR). The results showed that the enzymes associated with fiber degradation were higher in goat and sheep feces compared to cattle and rabbit's feces. Correlation analysis revealed that Bacillus and Fibrobacter were positively correlated with five types of fiber-degrading related enzymes. Notably, the relative abundance of Bacillus in the feces of Tibetan sheep was significantly higher than that of other five herbivores. A strain TS5 with good cellulose decomposition ability from the feces of Tibetan sheep by Congored staining, filter paper decomposition test, and enzyme activity determination was isolated. The strain was identified as Bacillus velezensis by biological characteristics, biochemical analysis, and 16S rRNA gene sequencing. To test the probiotic properties of Bacillus velezensis TS5, we evaluated its tolerance to acid and bile salt, production of digestive enzymes, antioxidants, antibacterial activity, and adhesion ability. The results showed that the strain had good tolerance to pH 2.0 and 0.3% bile salts, as well as good potential to produce cellulase, protease, amylase, and lipase. This strain also had good antioxidant capacity and the ability to antagonistic Staphylococcus aureus BJ216, Salmonella SC06, Enterotoxigenic Escherichia coli CVCC196, and Escherichia coli ATCC25922. More importantly, the strain had good self-aggregation and Caco-2 cell adhesion rate. In addition, we tested the safety of Bacillus velezensis TS5 by hemolysis test, antimicrobial susceptibility test, and acute toxicity test in mice. The results showed that the strain had no hemolytic phenotype, did not develop resistance to 19 commonly used antibiotics, had no cytotoxicity to Caco-2, and did not have acute toxic harm to mice. In summary, this study targeted isolated and screened a strain of Bacillus velezensis TS5 with high fiber-degrading ability and probiotic potency. This strain can be used as a potential probiotic for feeding microbial preparations for ruminants.

BNC-rSS, a bivalent subunit nanovaccine affords the cross-protection against Streptococcus agalactiae and Streptococcus iniae infection in tilapia

Streptococcal disease has severely restricted the development of global tilapia industry, which is mainly caused by Streptococcus agalactiae (S. agalactiae) and Streptococcus iniae (S. iniae). Vaccination has been proved to be a potential strategy to control it. In this study, a multi-epitope subunit vaccine Sip-Srr (SS) was prepared based on the B-cell antigenic epitopes prediction and multiple sequence alignment analysis of Sip and Srr sequences. Furthermore, the BNC-rSS nanocarrier vaccine system was constructed by connecting the rSS protein with modified bacterial nanocellulose (BNCs) and characterized by Fourier Transform Infrared Spectroscopy and Scanning Electron Microscope, the immersion immune effect against S. agalactiae and S. iniae infection was evaluated. The results showed that compared with the control group, BNC-rSS significantly enhanced serum antibody production, related enzyme activities and immune-related genes expression. It was noteworthy that BNC-rSS vaccine improved immune protection of tilapia, with survival rates of 66.67 % (S. agalactiae) and 60.00 % (S. iniae), respectively, compared with those of rSS vaccine (30 % and 33.33 %, respectively). Our study indicated that the BNC-rSS nanovaccine could elicit robust immune responses in tilapia by immersion immunization, and had the potential to offer cross-protection against S. agalactiae and S. iniae infection in tilapia.

Production of a potential multistrain probiotic in co-culture conditions using agro-industrial by-products-based medium for fish nutrition

BACKGROUND

Probiotics are viable microorganisms that when administered in adequate amounts confer health benefits to the host. In fish, probiotic administration has improved growth, and immunological parameters. For this reason, it is necessary production of probiotic bacteria, however, commercial culture mediums used for probiotic growth are expensive, so the design of a "low" cost culture medium is necessary. Therefore, this research aimed to produce a potential multistrain probiotic preparation composed of L. lactis A12 and Priestia species isolated from Nile tilapia (Oreochromis niloticus) gut using an agro-industrial by-products-based culture medium.

RESULTS

A Box-Behnken design with three factors (whey, molasses, and yeast extract concentration) was used. As the main results, a high concentration of three components enhanced the viability of L. lactis A12, however, viable cell counts of Priestia species were achieved at low molasses concentrations. The Optimal conditions were 1.00% w/v whey, 0.50% w/v molasses, and 1.50% w/v yeast extract. L. lactis A12 and Priestia species viable counts were 9.43 and 6.89 Log10 CFU/mL, respectively. L. lactis A12 concentration was higher (p < 0.05) in the proposed medium compared to commercial broth.

CONCLUSIONS

It was possible to produce L. lactis A12 and Priestia species in co-culture conditions. Whey and molasses were suitable components to produce the multistrain preparation. The cost of the proposed culture medium was 77.54% cheaper than the commercial medium. The proposed culture medium could be an alternative to commercial mediums for the production of this multistrain probiotic.

Synbiotic Agents and Their Active Components for Sustainable Aquaculture: Concepts, Action Mechanisms, and Applications

Aquaculture is a fast-emerging food-producing sector in which fishery production plays an imperative socio-economic role, providing ample resources and tremendous potential worldwide. However, aquatic animals are exposed to the deterioration of the ecological environment and infection outbreaks, which represent significant issues nowadays. One of the reasons for these threats is the excessive use of antibiotics and synthetic drugs that have harmful impacts on the aquatic atmosphere. It is not surprising that functional and nature-based feed ingredients such as probiotics, prebiotics, postbiotics, and synbiotics have been developed as natural alternatives to sustain a healthy microbial environment in aquaculture. These functional feed additives possess several beneficial characteristics, including gut microbiota modulation, immune response reinforcement, resistance to pathogenic organisms, improved growth performance, and enhanced feed utilization in aquatic animals. Nevertheless, their mechanisms in modulating the immune system and gut microbiota in aquatic animals are largely unclear. This review discusses basic and current research advancements to fill research gaps and promote effective and healthy aquaculture production.

Improvement of water quality with probiotics inclusion during simulated transport of Yellowfin Seabream Acanthopagrus latus larvae

OBJECTIVE

The expansion of marine aquaculture requires the shipment of early life stages from hatcheries to breeding centers. Thus, maintaining water quality parameters during transportation is crucial. This experiment investigated the effects of a commercial probiotic mixture (PM) (consisting of Bacillus licheniformis, Bacillus subtilis, Pediococcus acidilactici, and Lactobacillus acidophilus with a total count of 107  CFU/g) on water quality, bacterial population, and the survival of larvae of Yellowfin Seabream Acanthopagrus latus during a 24-h simulated transportation experiment.

METHODS

To simulate transportation, purified seawater was used as a control and purified seawater supplemented with 3 g of PM was used as the PM48 treatment. For the PM48 treatment, 3 g of PM was added to 1 L of purified seawater and mixed with 200 L of purified seawater 48 h prior to the main experiment.

RESULT

The use of probiotics resulted in an increase in larval survival up to 93.3% compared with 89.85% in the control group. Initial sampling showed a statistically significant difference inNO 2 - levels between the control and PM48 treatments. After transportation, the pH of the control treatment showed a significant decrease. The total number of bacteria and the total number of Vibrio spp. in water and fish larvae showed that within 48 h, the probiotics became the dominant population in the PM48 treatment. After 24 h, water samples and larvae from the control treatment showed a significant increase in bacterial load.

CONCLUSION

The results showed that probiotics can play a significant role in maintaining biotic and abiotic water quality parameters, leading to a better survival rate of larvae during transportation. These findings represent an important step in improving long-distance transport protocols.

Unlocking the Gut's Treasure: Lipase-Producing Bacillus subtilis Probiotic from the Intestine of Microstomus kitt (Lemon sole)

The main objective of this research was to identify potential probiotic candidates belonging to the Bacillus species that could demonstrate tolerance to bile salt and acidic conditions. The study focused on isolating Bacillus strains from the intestine of marine fish-Microstomus kitt. The isolation process involved the use of selective MRS media through the pour plate method. After 24 h, one particular isolate was identified based on its morphological and biochemical traits as Bacillus species. To confirm the identity, molecular characterization of the 16S RNA from the isolated strain was performed, and the sequence analysis verified it as Bacillus subtilis strain ACL_BS 001. With the molecular confirmation, the next step was to assess the probiotic characteristics of this B. subtilis strain. Various tests were conducted to evaluate its acid/pH tolerance, NaCl tolerance, and bile salt tolerance. The results indicated that B. subtilis exhibited high viability percentages even under acidic pH, in the presence of 1.5% bile salt, and at high salt concentrations. Subsequently, we investigated the strain's ability to produce lipase, an important enzyme with potential industrial applications. B. subtilis was grown in MRS agar amended with olive oil as a lipase substrate. After incubation, the presence of lipase activity was confirmed, and the enzymatic assay revealed a significant lipase enzyme activity of 100.23 µmoles/ml of the sample. In conclusion, the study successfully isolated and identified B. subtilis from the intestine of Microstomus kitt, and the strain exhibited promising probiotic characteristics, including resistance to bile salt and acidic conditions. Furthermore, the strain was found to produce lipase, which opens up possibilities for future research focusing on isolating and purifying the lipase from this potential probiotic B. subtilis strain.

Acute thermal stress increased enzyme activity and muscle energy distribution of yellowfin tuna

Heat is a powerful stressor for fish living in natural and artificial environments. Understanding the effects of heat stress on the physiological processes of fish is essential for better aquaculture and fisheries management. In this experiment, a heating rod was used to increase the temperature at 2°C/h to study the changes of energy allocation (CEA) and energy metabolity-related enzyme activities, including pepsin, trypsin, amylase, lipase, acid phosphatase, lactate dehydrogenase, alanine aminotransferase, glutamic oxalic aminotransferase and energy reserve (Ea), energy expenditure (ETS), in juvenile yellowfin tuna cells under acute temperature stress. The results showed that the Ea of juvenile yellowfin tuna muscles in response to high temperature (34°C) was significantly lower than that of the control (28°C), and it also increased ETS. At 6 h, CEA decreased slightly in the high-temperature group, but, the difference in CEA between 24 h and 0 h decreased. After heat stress for 6 h, the activities of acid phosphatase (ACP), lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and glutamic oxalacetic transaminase (AST) increased, indicating that the metabolic rate was accelerated. After heat stress for 24 h, the activity of ALT decreased, indicating that with time elapsed, the activities of some protein metabolizing enzymes increased, and some decreased. In this study, digestive enzymes, trypsin and lipase increased gradually. After heat stress, Ea and Ec change significantly. Yellowfin tuna muscles use lipids in response to sharp temperature increases at high temperatures, red muscles respond to temperature changes by increasing energy in the early stages, but not nearly as much, and white muscles reduce lipids.

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.

Bioassay and Whole-Genome Analysis of Bacillus velezensis FIO1408, a Biocontrol Agent Against Pathogenic Bacteria in Aquaculture

Bacterial disease is one of the most critical problems in aquaculture. Probiotics represent a promising biological approach to control bacterial disease because it is effective against pathogens and environmentally friendly. This study assessed the antagonistic activities of a bacterial strain FIO1408 isolated from deep-sea water against many pathogenic bacteria in aquaculture, including Listonella anguillarum, Vibrio parahaemolyticus, Vibrio alginolyticus, Aeromonas hydrophila, Edwardsiella anguillarum, Edwardsiella tarda, and Edwardsiella piscicida. The complete genome of strain FIO1408 consisted of a circular chromosome of 4,137,639 bp and two plasmids of 16,439 bp and 24,472 bp. Phylogenetic analysis showed strain FIO1408 clustered with Bacillus velezensis strains. 12 genes/gene clusters responsible for the synthesis of secondary metabolites were identified in the FIO1408 genome, including three lipopeptides, three polyketides, three bacteriocins, one siderophore, one dipeptide, and one unknown type. Also identified were 273 unique orthologous genes primarily involved in phage resistance, protein hydrolysis, environmental survivability, and genetic stability compared to B. velezensis KACC 13105, B. velezensis FZB42T, and B. velezensis NRRL B-41580. The principal safety of FIO1408 was demonstrated by genetic analyses and feeding trials. These findings will contribute to studies on the biocontrol mechanisms of B. velezensis FIO1408 and facilitate its application as a potent biological control agent against bacterial pathogens in aquaculture.

Positive effects of dietary Clostridium butyricum supplementation on growth performance, antioxidant capacity, immunity and viability against hypoxic stress in largemouth bass

The effects of dietary supplementation of Clostridium butyricum (CB) on growth performance, serum biochemistry, antioxidant activity, mRNA levels of immune-related genes and resistance to hypoxia stress were studied in largemouth bass. Feed with CB0 (control, 0 CFU/kg), CB1 (4.3×108 CFU/kg), CB2 (7.5×108 CFU/kg), CB3 (1.5×109 CFU/kg) and CB4 (3.2×109 CFU/kg) CB for 56 days, and then a 3 h hypoxic stress experiment was performed. The results showed that dietary CB significantly increased the WGR (weight gain rate), SGR (specific growth rate), PDR (protein deposition rate) and ISI (Intestosomatic index) of largemouth bass (P<0.05). Hepatic GH (growth hormone)/IGF-1 (insulin-like growth factor-1) gene expression was significantly upregulated in the CB3 and CB4 groups compared with the CB0 group (P<0.05), while the FC (feed conversion) was significantly decreased (P<0.05). Serum TP (total protein) and GLU (glucose) levels were significantly higher in the CB4 group than in the CB0 group (P<0.05), while the contents of serum AST (aspartate transaminase), ALT (alanine transaminase), AKP (alkline phosphatase) and UN (urea nitrogen) in CB4 were significantly lower than those in CB0 (P<0.05). T-AOC (total antioxidant capacity), SOD (superoxide dismutase), CAT (catalase), POD (peroxidase) and GSH-Px (glutathione peroxidase) activities were significantly higher in CB3 and CB4 groups than in CB0 group (P<0. 05). The liver MDA (malondialdehyde) content of CB1, CB2, CB3 and CB4 groups was significantly higher than that of CB0 group (P<0. 05). The relative expressions of IL-1β (interleukin 1β), TNF-α (tumor necrosis factor α) and TLR22 (toll-like receptor-22) genes in CB2, CB3 and CB4 groups were significantly lower than those in CB0 group (P<0.05). The relative expression of IL-8 (malondialdehyde) and MyD88 (Myeloid differentiation factor 88) genes in the CB4 group was significantly lower than that in the CB0 group (P<0.05). The liver LZM (lysozyme) content of CB2, CB3 and CB4 groups was significantly higher than that of CB0 group (P<0. 05). The relative expression of IL-10 (interleukin 10) and TGF-β (transforming growth factor β) genes in the CB4 group was significantly higher than that in the CB0 group (P<0.05). Under hypoxic stress for 3 h, the CMR of CB0 group was significantly higher than that of CB1, CB2, CB3 and CB4 groups (P<0.05). Dietary CB can improve the growth performance and resistance to hypoxic stress of largemouth bass by regulating the expression of GH/IGF-1 gene and inflammatory factors and inhibiting TLR22/MyD88 signaling pathway.

Cervicovaginal Bacillus velezensis Isolate: A Potential Probiotic and an Antagonist Against Candida and Staphylococcus

The cervicovaginal microbiota is an essential aspect of women's reproductive and overall health. In this study, we aimed to evaluate the probiotic properties of a cervicovaginal isolate, obtained from a gynecologically healthy woman and assess its antagonistic effect against various microorganisms isolated from the vagina. Cytological examination was performed using Papanicolaou staining, and the isolated microorganism was identified via 16S Ribosomal RNA Gene Sequence Analysis. Probiotic characteristics were evaluated by determining the tolerance of the isolate to low pH, different NaCl concentrations, and bile salts. Bacterial adherence to stainless steel sheets, antibiotic susceptibility, and antimicrobial activity tests were also conducted and analyzed. Antimicrobial tests and antagonistic activities were assessed through disc diffusion assays. The cervicovaginal isolate was identified as B. velezensis ON116948 and was found to be tolerant to low pH, high NaCl and 0.3% bile salts. Additionally, it exhibited adherence. With the exception of amoxicillin/clavulanic acid (AMC) (30 μg) and oxacillin (OX) (1 μg), this isolate was susceptible to all the antibiotics tested. Candida species did not grow on B. velezensis spread media, while B. velezensis was able to grow on C. albicans, C. glabrata, C. tropicalis, S. condimenti and S. epidermidis spread media with growth zones of 13.7 ± 0.6, 13.3 ± 0.6, 14.2 ± 4.4, 10.5 ± 0.5 and 16.0 ± 1.0 (around discs), respectively. Our findings suggest that the cervicovaginal B. velezensis ON116948 isolate exhibits probiotic properties and antagonistic activity. These results provide important insights into the potential use of this isolate as a probiotic for the prevention of vaginal infections.

Current Status of Probiotics in European Sea Bass Aquaculture as One Important Mediterranean and Atlantic Commercial Species: A Review

European sea bass production has increased in recent decades. This increase is associated with an annually rising demand for sea bass, which encourages the aquaculture industries to increase their production to meet that demand. However, this intensification has repercussions on the animals, causing stress that is usually accompanied by dysbiosis, low feed-conversion rates, and immunodepression, among other factors. Therefore, the appearance of pathogenic diseases is common in these industries after immunodepression. Seeking to enhance animal welfare, researchers have focused on alternative approaches such as probiotic application. The use of probiotics in European sea bass production is presented as an ecological, safe, and viable alternative in addition to enhancing different host parameters such as growth performance, feed utilization, immunity, disease resistance, and fish survival against different pathogens through inclusion in fish diets through vectors and/or in water columns. Accordingly, the aim of this review is to present recent research findings on the application of probiotics in European sea bass aquaculture and their effect on growth performance, microbial diversity, enzyme production, immunity, disease resistance, and survival in order to help future research.

Effects of choline supplementation on growth performance, liver histology, nonspecific immunity and related genes expression of hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatu) fed with high-lipid diets

This study was conducted to evaluate the effect of dietary choline levels on growth performance, liver histology, nonspecific immunity and related gene expression of hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatus) fed with high-lipid diets. The fish (initial body weight 6.86 ± 0.01 g) were fed diets containing different choline levels (0, 5, 10, 15, and 20 g/kg, named D1, D2, D3, D4, and D5, respectively) for 8 weeks. The results showed that:(1) dietary choline levels had no significant effect on final body weight (FBW), feed conversion rate (FCR), visceral somatic index(VSI) and condition factor (CF) compared with the control group (P > 0.05). However, the hepato somatic index (HSI) in the D2 group was significantly lower than that in the control group and the survival rate (SR) in the D5 group was significantly lower (P < 0.05). (2) with dietary choline level increasing, alkaline phosphatase (AKP) and superoxide dismutase (SOD) of serum showed a tendency to increase and then decrease, and the maximum values were obtained in the D3 group, but the contents of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) decreased significantly (P < 0.05). (3) Immunoglobulin M (IgM), lysozyme (LYZ), catalase (CAT), total antioxidative capacity (T-AOC), and SOD in the liver all showed a trend of first increase and then decrease with the dietary choline level increased, and all of them achieved the maximum value at D4 group (P < 0.05), while reactive oxygen species (ROS) and malondialdehyde (MDA) in the liver decreased significantly (P < 0.05). (4) results from liver sections suggest that appropriate levels of choline can improve cell structure, compared with the control group, the damaged histological morphology of the liver was relieved and even returned to normal in D3 group. (5) in the D3 group, choline significantly upregulated the expression of hepatic sod and cat mRNA, whereas the expression of cat in the D5 group was significantly lower than that in the control group (P < 0.05); And the supply of choline stimulated a significant down-regulation of interleukin 6 (il6), myeloid differentiation factor 8 (myd88), toll-like receptor 22 (tlr22) mRNA expression levels in liver, while the expression of cellular tumor antigen p53 (p53) and interleukin 10 (il10) showed an upward and then downward trend (P < 0.05). In general, choline can improve the immunity of hybrid grouper by regulating non-specific immune-related enzyme activity and gene expression and reducing oxidative stress induced by high-lipid diet.

The Genetic and Phenotypic Diversity of Bacillus spp. from the Mariculture System in China and Their Potential Function against Pathogenic Vibrio

Bacillus spp. could be one of the most suitable substitutes for the control and prevention of aquatic diseases. The occurrence of species population, antimicrobial character, and virulence diversity in Bacillus spp. recovered from the mariculture system in China between 2009 and 2021 were investigated, screening for probiotic Bacillus strains with good biological safety that can inhibit Vibrio parahaemolyticus, V. alginolyticus, V. harveyi, V. owensii, V. campbellii. The results showed that 116 Bacillus isolates were divided into 24 species, and the top three species were B. subtilis (37/116), B. velezensis (28/116), and B. amyloliquefaciens (10/116). Among the 116 Bacillus isolates, 32.8% were effective against V. parahaemolyticus, 30.1% for V. alginolyticus, 60.3% for V. harveyi, 69.8% for V. owensii and 74.1% for V. campbellii. More than 62% of Bacillus isolates were susceptible to florfenicol, doxycycline and tetracycline, etc., and 26/116 Bacillus isolates were found to be multiple-antibiotic-resistant (MAR), with MARI values ranging from 0 to 0.06. Eighteen kinds of antibiotic resistance genes were tested; only tetB, blaTEM, and blaZ were detected. And 9 isolates in 2 Bacillus species were excluded by 6/10 kinds of Bacillus-related toxin gene (hblA, hblC, nheB, nheC, entFM, cykK). Bio-safety testing indicated that three kinds of probiotics were good probiotic candidates to prevent Vibriosis. These results provide comprehensive genetic diversity, potential risks, and probiotic characteristics of Bacillus in the mariculture system in China, and provide basic support for green and healthy development of aquatic industry.

A new isolate of Streptomyces lateritius (Z1-26) with antibacterial activity against fish pathogens and immune enhancement effects on crucian carp (Carassius auratus)

The Streptomyces lateritius Z1-26 was isolated from soil samples which showed broad-spectrum antibacterial activity against a broad range of fish pathogens. The In Vivo Imaging System (IVIS) monitored that strain Z1-26 could survive and colonize in the gills and abdomen of crucian carp. The effects of dietary supplementation with strain Z1-26 were evaluated with respect to the growth performance, antioxidant capacity, and immune response of crucian carp. The results showed that the Z1-26-fed fish had a significantly higher growth rate than the fish fed the control diet. The immune and antioxidant parameters revealed that the non-specific immune indicators (AKP, SOD, and LZM) of the serum, the expression of immune-related genes (IgM, C3, and LZM), and antioxidant-related genes (Nrf2 and Keap1) of the immune organs were significantly increased, whereas the expression of pro-inflammatory factors (IL-1β, IL-8, and TNF-α) of the immune organs was significantly down-regulated in crucian carp fed strain Z1-26 compared with fish fed a control diet. Moreover, fish fed with Z1-26 supplemented diets showed a significantly improved survival rate after Aeromonas hydrophila infection. In addition, the whole genome analysis showed that strain Z1-26 possesses 28 gene clusters, including 6 polyketide synthetase (PKS), 4 non-ribosomal peptide-synthetase (NRPS), 1 bacteriocin, and 1 lantipeptide. In summary, these results indicated that strain Z1-26 could improve the growth performance and disease resistance in crucian carp, and has the potential to be developed as a candidate probiotics for the control of bacterial diseases in aquaculture.

Effects of Dietary Supplementation with Bacillus amyloliquefaciens US573 on Intestinal Morphology and Gut Microbiota of European Sea Bass

Probiotics or direct-fed microbials (DFM) have proven strong potential for improving aquaculture sustainability. This study aims to evaluate the effects of dietary supplementation with the DFM Bacillus amyloliquefaciens US573 on growth performance, intestinal morphology, and gut microbiota (GM) of European sea bass. For this purpose, healthy fish were divided into two feeding trials in triplicate of 25 fish in each tank. The fish were fed with a control basal diet or a DFM-supplemented diet for 42 days. Results showed that, while no significant effects on growth performance were observed, the length and abundance of villi were higher in the DFM-fed group. The benefic effects of DFM supplementation included also the absence of cysts formation and the increase in number of goblet cells playing essential role in immune response. Through DNA metabarcoding analysis of GM, 5 phyla and 14 major genera were identified. At day 42, the main microbiome changes in response to B. amyloliquefaciens US573 addition included the significant decrease in abundance of Actinobacteria phylum that perfectly correlates with a decrease in Nocardia genus representatives which represent serious threat in marine and freshwater fish. On the contrary, an obvious dominance of Betaproteobacteria associated with the abundance in Variovorax genus members, known for their ability to metabolize numerous substrates, was recorded. Interestingly, Firmicutes, particularly species affiliated to the genus Sporosarcina with recent promising probiotic potential, were identified as the most abundant. These results suggest that B. amyloliquefaciens US573 can be effectively recommended as health-promoting DFM in European sea bass farming.

Influences of Bacillus subtilis and fructooligosaccharide on growth performances, immune responses, and disease resistance of Nile tilapia, Oreochromis niloticus

The present study investigated the effects of Bacillus subtilis and fructooligosaccharide (FOS) on growth performances, immunity improvement, and disease resistance of Nile tilapia (Oreochromis niloticus). The fish (24.5 ± 1.6 g) were fed a basal diet (G1), diets supplemented with 1 g/kg (G2), 3 g/kg (G3) and 5 g/kg (G4) of FOS as well as diets supplemented with 1 × 10⁹ CFU/g (G5), 3 × 10⁹ CFU/g (G6) and 5 × 10⁹ CFU/g (G7) of B. subtilis for 56 days. After the feeding trial, the complement C3, IL-1β, TNF-α, IFN-γ, hsp70 gene expression in the liver was then analyzed by a quantitative Real-time PCR. Then, fish were infected with Streptococcus agalactiae, and the survival rate was recorded. The results showed that FOS and B. subtilis had no significant effect (P > 0.05) on growth performances and survival rate. Lysozyme activity was significantly greater in the G4, G5, G6, and G7 groups. Also, all fish fed FOS and B. subtilis showed significantly (P < 0.05) higher respiratory burst activity than other groups. The expressions of complement C3, IL-1β, TNF-α, IFN-γ, and hsp-70 in the liver were significantly higher for fish fed 5 g/kg of FOS as well as for fish that received any concentration level of B. subtilis (P < 0.05) used in the study. After the S. agalactiae challenge test, the survival rate of fish-fed diets supplemented with FOS and B. subtilis was slightly higher than for the control group. The results indicated that FOS and B. subtilis could stimulate immune responses and immune-related genes in tilapia. However, further investigation of other prebiotics or herbs in combination with B. subtilis is encouraged at molecular levels and screening for beneficial metabolites that may increasingly improve digestive enzymes, growth performances, and health benefits in tilapia. In addition, on-farm experiments are needed.

Bacillus Species as Direct-Fed Microbial Antibiotic Alternatives for Monogastric Production

Antibiotic growth promoters have been utilized for long time at subtherapeutic levels as feed supplements in monogastric animal rations. Because of their side-effects such as antibiotic resistance, reduction of beneficial bacteria in the gut, and dysbiosis, it is necessary to look for non-therapeutic alternatives. Probiotics play an important role as the key substitutes to antibacterial agents due to their many beneficial effects on the monogastric animal host. For instance, enhancement of the gut microbiota balance can contribute to improvement of feed utilization efficiency, nutrients absorption, growth rate, and economic profitability of livestock. Probiotics are defined as "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host." They are available in diverse forms for use as feed supplements. Their utilization as feed additives assists in good digestion of feed ingredients and hence, making the nutrients available for promoting growth. Immunity can also be enhanced by supplementing probiotics to monogastrics diets. Moreover, probiotics can help in improving major meat quality traits and countering a variety of monogastric animals infectious diseases. A proper selection of the probiotic strains is required in order to confer optimal beneficial effects. The present review focuses on the general functional, safety, and technological screening criteria for selection of ideal Bacillus probiotics as feed supplements as well as their mechanism of action and beneficial effects on monogastric animals for improving production performance and health status.

Cross-habitat distribution pattern of Bacillus communities and their capacities of producing industrial hydrolytic enzymes in Paracel Islands: Habitat-dependent differential contributions of the environment

Bacillus as a predominant genus of enzyme-producing bacteria presents desirable features to fulfill the vast demand of specific industries, whereas the knowledge of the Bacillus communities and their capacities of producing industrial hydrolytic enzymes across the microhabitats of the Paracel Islands is limited. Herein, a total of 193 culturable Bacillus strains belonging to 19 species were isolated across the microhabitats of seawater, sediment, coral and seagrass, covering 39 stations of the Paracel Islands. Each microhabitat displayed its unique species, while the species of Bacillus paramycoides besides being the dominant species with an abundance of 54.94% also was the only species shared by all microhabitats of the Paracel Islands. Of the Bacillus communities, 97.41% of the isolates exhibited the capacity of producing one-or-more types of enzymes with comparatively higher and broader ranges of enzyme activities, including 163 protease-, 27 cellulase-, 118 alginate lyase-, 140 K-carrageenase- and 158 agarose-producing strains. By the correlation analyses of "Bacillus-environmental factors" and "Enzyme-producing Bacillus-environmental factors", the cross-habitat distribution and enzyme-producing capacity pattern of the Bacillus communities were strongly driven by habitat type, and the environmental factors made habitat-dependent differential contributions to that in the Paracel Islands. It's worth noting that the cellulase-producing strain wasn't detected in seagrass due to its survival strategy to prevent cellulose degradation by inhibiting cellulase-producing bacteria, while coral contained more stable microbial metabolic functions to protect against environmental fluctuations. These findings besides providing large quantities of promising enzyme-producing candidates for specific industrial desires, also facilitate the development and utilization of marine microbial resources and the environmental policy- and/or law-making according to environmental features across the microhabitats of the Paracel Islands.

Probiotics Bacillus cereus and B. subtilis reshape the intestinal microbiota of Pengze crucian carp (Carassius auratus var. Pengze) fed with high plant protein diets

The intestinal dysfunction induced by high plant protein diets is frequently observed in farmed fish, and probiotics of Bacillus genus were documented to benefit the intestinal health through the modulation of intestinal microbiota without clearness in its underlying mechanism yet. Fusobacteria, Proteobacteria, and Firmicutes were observed to be the dominate phyla, but their proportion differentiated in the intestinal bacterial community of Pengze crucian carp (Carassius auratus var. Pengze) fed different diets in this study. Dietary supplementation of B. cereus and B. subtilis could reshape the intestinal bacterial community altered by high plant protein diets through a notable reduction in opportunistic pathogen Aeromonas together with an increase in Romboutsia and/or Clostridium_sensu_stricto from Firmicutes. Due to the alteration in the composition of bacterial community, Pengze crucian carp exhibited characteristic ecological networks dominated by cooperative interactions. Nevertheless, the increase in Aeromonas intensified the competition within bacterial communities and reduced the number of specialists within ecological network, contributing to the microbial dysbiosis induced by high plant protein diets. Two probiotics diets promoted the cooperation within the intestinal bacterial community and increased the number of specialists preferred to module hubs, and then further improved the homeostasis of the intestinal microbiota. Microbial dysbiosis lead to microbial dysfunction, and microbial lipopolysaccharide biosynthesis was observed to be elevated in high plant protein diets due to the increase in Aeromonas, gram-negative microbe. Probiotics B. cereus and B. subtilis restored the microbial function by elevating their amino acid and carbohydrate metabolism together with the promotion in the synthesis of primary and secondary bile acids. These results suggested that dietary supplementation of probiotics B. cereus and B. subtilis could restore the homeostasis and functions of intestinal microbiota in Pengze crucian carp fed high plant protein diets.

Improvement of aquaculture water quality by mixed Bacillus and its effects on microbial community structure

Microbial remediation, especially the application of probiotics, has recently gained popularity in improving water quality and maintaining aquatic animal health. The efficacy and mechanism of mixed Bacillus for improvement of water quality and its effects on aquatic microbial community structure remain unknown. To elucidate these issues, we applied two groups of mixed Bacillus (Bacillus megaterium and Bacillus subtilis (A0 + BS) and Bacillus megaterium and Bacillus coagulans (A0 + BC)) to the aquaculture system of Crucian carp. Our results showed that the improvement effect of mixed Bacillus A0 + BS on water quality was better than that of A0 + BC, and the NH₄⁺-N, NO₂^--N, NO₃^--N, and total phosphorus (TP) concentrations were reduced by 46.3%, 76.3%, 35.6%, and 80.3%, respectively. In addition, both groups of mixed Bacillus increased the diversity of the bacterial community and decreased the diversity of the fungal community. Microbial community analysis showed that mixed Bacillus A0 + BS increased the relative abundance of bacteria related with nitrogen and phosphorus removal, such as Proteobacteria, Actinobacteria, Comamonas, and Stenotrophomonas, but decreased the relative abundance of pathogenic bacteria (Acinetobacter and Pseudomonas) and fungi (Epicoccum and Fusarium). Redundancy analysis showed that NH₄⁺-N, NO₂^--N, and TP were the primary environmental factors affecting the microbial community in aquaculture water. PICRUST analysis indicated that all functional pathways in the A0 + BS group were richer than those in other groups. These results indicated that mixed Bacillus A0 + BS addition produced good results in reducing nitrogenous and phosphorus compounds and shaped a favorable microbial community structure to further improve water quality.

Comparative transmission of bacteria from Artemia salina and Brachionus plicatilis to the cnidarian Nematostella vectensis

The microbial community associated with animals (microbiome) is essential for development, physiology, and health of host organisms. A critical step to understand the assembly of microbiomes is to determine how effectively bacteria colonize and establish within the host. Bacteria commonly colonize hosts through vertical transmission, passively from the environment, or through food consumption. Using the prey feeding method (PFM), we test transmittance of Bacillus velezensis, Pseudoalteromonas spiralis, and Vibrio alginolyticus to Nematostella vectensis using two prey, Artemia salina and Brachionus plicatilis. We compare PFM to a solution uptake method (SUM) to quantify the concentration of bacteria in these host organisms, with plate counts. Larvae had a similar uptake with SUM at 6 h but had greater concentrations at 48 h versus PFM. Juveniles acquired similar concentrations at 6 h for SUM and PFM using B. plicatilis and A. salina. At 2 days, the quantity of bacteria vectored from PFM increased. After 7 days the CFUs decreased 2-fold with B. plicatilis and A. salina relative to the 2-day concentrations, and further decreased after 14 days. Therefore, prey-mediated methods provide greater microbe transplantation than SUM after 24 h, supporting this approach as a more successful inoculation method of individual bacterial species.

Characterization and protective effect against ultraviolet radiation of a novel exopolysaccharide from Bacillus marcorestinctum QDR3-1

Although exopolysaccharide (EPS) has been applied to various fields, EPS for UVR-mediated oxidative stress repair still needs further exploration. In this study, a novel EPS was isolated from the fermentation medium of Bacillus sp. QDR3-1 and its yield was 4.8 g/L (pH 8.0, 12 % glucose, 30 °C and 6 % NaCl). The pure fraction (named EPS-M1) was purified by DEAE-cellulose and Sephadex G-100 column. EPS-M1 was a heteropolysaccharide composed of Man, Glc, Gal, and Fuc with a molecular weight of 33.8 kDa. Scanning electron microscopy (SEM) observed a rough surface and reticular structure of EPS-M1, and EPS-M1 formed spherical aggregates in aqueous solution observed in atomic force microscopy (AFM). Thermal analysis revealed that the degradation temperature of EPS-M1 was 306 °C. Moreover, methylation and NMR analysis determined that EPS-M1 was consisted of →3)-Manp-(1→, →2,6)-Manp-(1→, →4,6)-Glcp-(1→, →3)-Glcp-(1→, →4)-Galp-(1→, →4)-Fucp-(1→, and T-Manp-(1→. Furthermore, the cytotoxicity and the repair ability of UVR-mediated cell damage of EPS-M1 were studied with L929 cells. The results showed that EPS-M1 had good biocompatibility and it could mitigate UVR-mediated cell damage by regulating the levels of cellular reactive oxygen species (ROS), depolarization of mitochondrial membrane potential (MMP) and Caspase-3/7 activity. Overall, the structure analysis and the protective effects of EPS against L929 cells exposed to UVR provided an experimental basis for EPS in practical applications.

Impacts of tea polyphenols on growth, antioxidant capacity and immunity in juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) fed high-lipid diets

The experiment aimed to investigate the alteration of tea polyphenols (TP) in growth and immunity for hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) fed high-lipid diets. Six concentrations of TP (0, 0.01, 0.02, 0.04, 0.08, 0.16%, named TP1 (basic diet control), TP2, TP3, TP4, TP5, TP6) were supplied in isonitrogenous (51%) and isolipidic (16.7%) experimental diets. These diets were fed to the juvenile grouper (8.68 ± 0.22 g) for 8 weeks. The results showed that dietary TP significantly increased the weight gain rate and specific growth rate (P < 0.05), compared with the control group. The protein efficiency ratio in TP4 group was significantly higher than that of the control group (P < 0.05). TP supplement in high-lipid diets increased antioxidant capacity in the serum (CAT, GSH-Px, T-AOC) and liver (SOD, CAT, GSH-Px, T-AOC). Additionally, dietary TP decreased oxidative stress (ROS, MDA) and improved immunity (ACP, AKP, LYS, IgM) in the liver. The histology of hepatic tissue indicated that dietary TP alleviated pathological symptoms caused by high-lipid diets. Compared with the control group, appropriate dietary TP significantly up-regulated expression of sod, cat, gsh-px, nrf2, keap1, hsp70, hsp90, myd88, tnfα and down-regulated expression of tlr22, il8, il1β, il10 in the liver (P < 0.05). In the head kidney, expression of myd88, il1β, tnfα and il6 were significantly up-regulated and expression of tlr22 and il10 were significantly down-regulated by dietary TP (P < 0.05). After the challenge of Vibrio harveyi, survival rate in higher doses of TP group (TP4 ∼ TP6) was evidently higher, compared with the control group. In conclusion, TP supplement in high-lipid diets improved antioxidant capacity and enhanced immunity of grouper. We speculate that TP may play the role of an immunostimulant, enhancing immunity and disease resistance by cytokine-medicated immune responses. Based on the second-order regression, 0.092-0.106% tea polyphenols were recommended in juvenile grouper high-lipid diets.

Use of Probiotic Bacteria and Bacteriocins as an Alternative to Antibiotics in Aquaculture

In addition to their use in human medicine, antimicrobials are also used in food animals and aquaculture, and their use can be categorized as therapeutic against bacterial infections. The use of antimicrobials in aquaculture may involve a broad environmental application that affects a wide variety of bacteria, promoting the spread of bacterial resistance genes. Probiotics and bacteriocins, antimicrobial peptides produced by some types of lactic acid bacteria (LAB), have been successfully tested in aquatic animals as alternatives to control bacterial infections. Supplementation might have beneficial impacts on the intestinal microbiota, immune response, development, and/or weight gain, without the issues associated with antibiotic use. Thus, probiotics and bacteriocins represent feasible alternatives to antibiotics. Here, we provide an update with respect to the relevance of aquaculture in the animal protein production sector, as well as the present and future challenges generated by outbreaks and antimicrobial resistance, while highlighting the potential role of probiotics and bacteriocins to address these challenges. In addition, we conducted data analysis using a simple linear regression model to determine whether a linear relationship exists between probiotic dose added to feed and three variables of interest selected, including specific growth rate, feed conversion ratio, and lysozyme activity.

Protective effect of protexin concentrate in reducing the toxicity of chlorpyrifos in common carp (Cyprinus carpio)

The present study aimed to evaluate the protective effect of protexin supplementation against chlorpyrifos-induced oxidative stress and immunotoxicity in Cyprinus carpio. After 21 days, the activity of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR), and total antioxidant levels significantly decreased in hepatocytes of fish exposed to chlorpyrifos, while malondialdehyde (MDA) increased. Treatment with protexin was able to reverse the decrease in SOD and GR and significantly reduce MDA levels. Exposure to chlorpyrifos also induced alterations in blood biochemical parameters and caused immunosuppression. Dietary protexin return some parameters (aspartate aminotransferase, lactate dehydrogenase, and γ-glutamyltransferase activities, and glucose, cholesterol, total protein, creatinine, and complement C4 levels) to values similar to those of the control group. Based on the results, it can be concluded that protexin exerted protective effects against chlorpyrifos exposure in C. carpio reducing oxidative damage, and ameriorating blood biochemical alterations and the immunosuppression.

Impact of Putative Probiotics on Growth, Behavior, and the Gut Microbiome of Farmed Arctic Char (Salvelinus alpinus)

Beneficial bacteria promise to promote the health and productivity of farmed fish species. However, the impact on host physiology is largely strain-dependent, and studies on Arctic char (Salvelinus alpinus), a commercially farmed salmonid species, are lacking. In this study, 10 candidate probiotic strains were subjected to in vitro assays, small-scale growth trials, and behavioral analysis with juvenile Arctic char to examine the impact of probiotic supplementation on fish growth, behavior and the gut microbiome. Most strains showed high tolerance to gastric juice and fish bile acid, as well as high auto-aggregation activity, which are important probiotic characteristics. However, they neither markedly altered the core gut microbiome, which was dominated by three bacterial species, nor detectably colonized the gut environment after the 4-week probiotic treatment. Despite a lack of long-term colonization, the presence of the bacterial strains showed either beneficial or detrimental effects on the host through growth rate enhancement or reduction, as well as changes in fish motility under confinement. This study offers insights into the effect of bacterial strains on a salmonid host and highlights three strains, Carnobacterium divergens V41, Pediococcus acidilactici ASG16, and Lactiplantibacillus plantarum ISCAR-07436, for future research into growth promotion of salmonid fish through probiotic supplementation.

Genetic Characteristics and Enzymatic Activities of Bacillus velezensis KS04AU as a Stable Biocontrol Agent against Phytopathogens

Bacillus velezensis has a broad application in the agricultural and industrial sectors for its biocontrol properties and its potential active secondary metabolites. The defined phenotypic characteristics of a strain vary according to its ecosystem. We report the complete genomic analysis of B. velezensis KS04AU compared to four strains of B. velezensis (SRCM102752, ONU-553, FZB42, and JS25R) and two closely related Bacillus amyloliquefaciens (LL3 and IT-45). A total of 4771 protein coding genes comprises the KS04AU genome, in comparison with 3334 genes core genes found in the six other strains and the remaining 1437 shell genes. Average nucleotide identity of the target strain to the six other strains showed 99.65% to B. velezensis ONU-553, sharing 60 orthologous genes. Secondary metabolite gene cluster analysis of all strains showed that KS04AU has a mersacidin cluster gene, which is absent in the genome of the other strains. PHASTER analysis also showed KS04AU harboring two phages (Aeribacllus AP45 NC_048651 and Paenibacillus_Tripp NC_028930), which were also unique in comparison with the other strains. Analysis on anti-microbial resistance genes showed no difference in the genome of KS04AU to any of the other genomes, with the exception of B. amyloliquefaciens IT-45 which had one unique small multidrug-resistance antibiotic efflux-pump gene (qacJ). The CRISPR-Cas systems in the strains were also compared showing one CRISPR gene found only in KS04AU. Hydrolytic activity, antagonistic activity against phytopathogens (Fusarium oxysporum, Fusarium graminearum, Alternaria alternata and Pseudomonas syringae) and biocontrol against tomato foot and root rot experiments were carried out. B. velezensis KS04AU inhibits the growth of all phytopathogens tested, produces hydrolytic activity, and reduces Fusarium oxysporum f.sp. radicis-lycopersici (Forl) ZUM2407 lesions up to 46.02 ± 0.12%. The obtained results confirm B. velezensis KS04AU as a potential biocontrol strain for plant protection.

The positive effects of dietary inositol on juvenile hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatu) fed high-lipid diets: Growthperformance, antioxidant capacity and immunity

The objective of the present research was to assess the influence of inositol supplementation on growth performance, histological morphology of liver, immunity and expression of immune-related genes in juvenile hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatu). Hybrid grouper (initial weight 6.76 ± 0.34 g) were fed isonitrogenous and isolipidic diets (16%) with various inositol levels of 0.17 g/kg (J1, the control group), 0.62 g/kg (J2), 1.03 g/kg (J3), 1.78 g/kg (J4), 3.43 g/kg (J5), 6.59 g/kg (J6), respectively. The growth experiment lasted for 8 weeks. The results indicated that dietary inositol had a significant promoting effect on final mean body weight of the J5 and J6 groups and specific growth rate (SGR) of the J3, J4, J5 and J6 groups (P < 0.05). In the serum, superoxide dismutase (SOD) of the J4 group became significantly active compared with that of the control group (P < 0.05), while aspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase (AKP) activities in the inositol-treated groups showed distinctly decreased compared with those of the control group (P < 0.05). In the liver, dietary inositol could significantly increase the activities of SOD, catalase (CAT), lysozyme (LYZ) and the contents of total antioxidative capacity (T-AOC) and immunoglobulin M (IgM) (P < 0.05), and distinctly reduce the content of malondialdehyde (MDA) as well as reactive oxygen species (ROS) (P < 0.05). Compared with the control group, the damaged histological morphology of the liver was relieved and even returned to normal after an inositol increase (0.4-3.2 g/kg). In the liver, the remarkable up-regulation of SOD, CAT, glutathione peroxidase (GPX), heat shock protein70 (HSP70) and heat shock protein90 (HSP90) expression levels were stimulated by supply of inositol, while interleukin 6 (IL6), interleukin 8 (IL8) and transforming growth factor β (TGF-β) expression levels were down-regulated by supply of inositol. In head kidney, the mRNA of toll-like receptor 22 (TLR22), myeloid differentiation factor 88 (MyD88) and interleukin 1β (IL1β) expression levels were significantly down-regulated (P < 0.05), which could further lead to remarkable down-regulation of IL6 and tumor necrosis factor α (TNF-α) expression (P < 0.05). These results indicated that high-lipid diets with supply of inositol promoted growth, increased the antioxidant capacity, and suppressed the inflammation of the liver and head kidney by inhibiting the expression of pro-inflammation factors (IL6, IL8, TGF-β and TNF-α). In conclusion, these results indicated that dietary inositol promoted growth, improved antioxidant capacity and immunity of hybrid grouper fed high-lipid diets. Based on SGR, broken-line regression analysis showed that 1.66 g/kg inositol supply was recommended in high-lipid diets of juvenile grouper.

Improving the nutritional value and bioactivity of soybean meal in solid-state fermentation using Bacillus strains newly isolated from the gut of the termite Termes propinquus

The present study aimed to isolate and characterize proteolytic Bacillus spp. from termite guts to test the possibility of application for improving the nutritional value and bioactivity of fermented soybean meal (FSBM). Aerobic endospore-forming bacteria were isolated from the gut of the termite Termes propinquus. Ten isolates with high levels of soy milk degradation were selected and tested for extracellular enzyme production. Among them, two isolates, Tp-5 and Tp-7, exhibited all tested hydrolytic enzyme activities (cellulase, xylanase, pectinase, amylase, protease, lipase and phytase), weak alpha hemolytic and also antagonistic activities against fish pathogenic species of Aeromonas and Streptococcus. Both phylogenetic and biochemical analyses indicated that they were closely related to Bacillus amyloliquefaciens. During solid-state fermentation of SBM, Tp-5 and Tp-7 exhibited the highest protease activity (1127.2 and 1552.4 U g-1, respectively) at 36 h, and the resulting FSBMs showed a significant increase in crude protein content and free radical-scavenging ability (P < 0.05), as well as an improvement in the composition of amino acids, metabolites and other nutrients, while indigestible materials such as fiber, lignin and hemicellulose were decreased. The potential strains, especially Tp-7, improved the nutritional value of FSBM by their strong hydrolytic and antioxidant activities, together with reducing antinutritional components.

Dietary supplementation with Weissella cibaria C-10 and Bacillus amyloliquefaciens T-5 enhance immunity against Aeromonas veronii infection in crucian carp (Carassiu auratus)

With the aim to discover novel lactic acid bacteria and Bacillus strains from fish as potential probiotics to replace antibiotics in aquaculture, the present study was conducted to isolate lactic acid bacteria and Bacillus from intestinal tract of healthy crucian carp (Carassiu auratus) and largemouth bass (Micropterus salmoides) and evaluate their resistance against Aeromonas veronii. Based on the evaluation of antibacterial activity and tolerance test, one strain of lactic acid bacteria (Weissella cibaria C-10) and one strain of Bacillus (Bacillus amyloliquefaciens T-5) with strong environmental stability were screened out. The safety evaluation showed that these two strains were non-toxic to crucian carp and were sensitive to most antibiotics. In vivo study, the crucian carps were fed a basal diet supplemented with W. cibaria C-10 (C-10), B. amyloliquefaciens T-5 (T-5) and W. cibaria C-10 + B. amyloliquefaciens T-5 (C-10+T-5), respectively, for 5 weeks. Then, various immune parameters were measured at 35 days of post-feeding. Results showed both probiotics could improve the activities of related immune enzymes, immune factors and non-specific immune antibodies in blood and organs (gill, gut, kidney, liver, and spleen) of crucian carp in varying degrees. Moreover, after 7 days of challenge experiment, the survival rates after challenged with A. veronii of W. cibaria C-10 (C-10), B. amyloliquefaciens T-5 (T-5) and W. cibaria C-10 + B. amyloliquefaciens T-5 (C-10+T-5) supplemented groups to the crucian carps were 20%, 33% and 22%, respectively. Overall, W. cibaria C-10 and B. amyloliquefaciens T-5 could be considered to be developed into microecological preparations for the alternatives of antibiotics in aquaculture.

Antibacterial Activity of Two Metabolites Isolated From Endophytic Bacteria Bacillus velezensis Ea73 in Ageratina adenophora

Ageratina adenophora, as an invasive and poisonous weed, seriously affects the ecological diversity and development of animal husbandry. Weed management practitioners have reported that it is very difficult to control A. adenophora invasion. In recent years, many researchers have focused on harnessing the endophytes of the plant as a useful resource for the development of pharmacological products for human and animal use. This study was performed to identify endophytes with antibacterial properties from A. adenophora. Agar well diffusion method and 16S rRNA gene sequencing technique were used to screen and identify endophytes with antibacterial activity. The response surface methodology and prep- high-performance liquid chromatography were used to determine the optimizing fermentation conditions and isolate secondary metabolites, respectively. UV-visible spectroscopy, infrared spectroscopy, nuclear magnetic resonance, and high-resolution mass spectrum were used to determine the structures of the isolated metabolites. From the experiment, we isolated a strain of Bacillus velezensis Ea73 (GenBank no. MZ540895) with broad-spectrum antibacterial activity. We also observed that the zone of inhibition of B. velezensis Ea73 against Staphylococcus aureus was the largest when fermentation broth contained 6.55 g/L yeast extract, 6.61 g/L peptone, 20.00 g/L NaCl at broth conditions of 7.95 pH, 51.04 h harvest time, and a temperature of 27.97°C. Two antibacterial peptides, Cyclo (L-Pro-L-Val) and Cyclo (L-Leu-L-Pro), were successfully extracted from B. velezensis Ea73. These two peptides exhibited mild inhibition against S. aureus and Escherichia coli. Therefore, we isolated B. velezensis Ea73 with antibacterial activity from A. adenophora. Hence, its metabolites, Cyclo (L-Pro-L-Val) and Cyclo (L-Leu-L-Pro), could further be developed as a substitute for human and animal antibiotics.

Dietary supplementation of Bacillus velezensis improves Vibrio anguillarum clearance in European sea bass by activating essential innate immune mechanisms

Bacillus spp. supplementation as probiotics in cultured fish diets has a long history of safe and effective use. Specifically, B. velezensis show great promise in fine-tuning the European sea bass disease resistance against the pathogenicity caused by several members of the Vibrio family. However, the immunomodulatory mechanisms behind this response remain poorly understood. Here, to examine the inherent immune variations in sea bass, two equal groups were fed for 30 days with a steady diet, with one treatment supplemented with B. velezensis. The serum bactericidal capacity against live cells of Vibrio anguillarum strain 507 and the nitric oxide and lysozyme lytic activities were assayed. At the cellular level, the phagocytic response of peripheral blood leukocytes against inactivated Candida albicans was determined. Moreover, head-kidney (HK) total leukocytes were isolated from previously in vivo treated fish with LPS of V. anguillarum strain 507. Mechanistically, the expression of some essential proinflammatory genes (interleukin-1 (il1b), tumor necrosis factor-alpha (tnfa), and cyclooxygenase 2 (cox2) and the sea bass specific antimicrobial peptide (AMP) dicentracin (dic) expressions were assessed. Surprisingly, the probiotic supplementation significantly increased all humoral lytic and cellular activities assayed in the treated sea bass. In addition, time-dependent differences were observed between the control and probiotic treated groups for all the HK genes markers subjected to the sublethal LPS dose. Although the il1b was the fastest responding gene to a significant level at 48 h post-injection (hpi), all the other genes followed 72 h in the probiotic supplemented group. Finally, an in vivo bacteria challenge against live V. anguillarum was conducted. The probiotic fed fish observed a significantly higher survival. Overall, our results provide clear vertical evidence on the beneficial immune effects of B. velezensis and unveil some fundamental immune mechanisms behind its application as a probiotic agent in intensively cultured European sea bass.

Mucosal and systemic immune effects of Bacillus subtilis in rainbow trout (Oncorhynchus mykiss)

Bacillus spp. are well known for their probiotic properties. Hence, the long-term feeding of Bacillus spp. strains to different fish species has been proved to confer beneficial effects regarding growth or pathogen resistance, among others. However, whether these strains could function as mucosal adjuvants, up-regulating immune responses after a single administration, has not yet been investigated in fish. Thus, in the current work, we have performed a series of experiments in rainbow trout (Oncorhynchus mykiss) aimed at establishing the potential of two Bacillus subtilis spore-forming strains, designated as ABP1 and ABP2, as oral adjuvants/immunostimulants. As an initial step, we evaluated their transcriptional effects on the rainbow trout intestinal epithelial cell line RTgutGC, and in gut tissue explants incubated ex vivo with the two strains. Their capacity to adhere to RTgutGC cells was also evaluated by flow cytometry. Although both strains had the capacity to modulate the transcription of several genes related to innate and adaptive immune responses, it was the ABP1 strain that led to stronger transcriptional effects, also exerting a higher binding capacity to intestinal epithelial cells. Consequently, we selected this strain to establish its effects on splenic B cells upon in vitro exposure as well as to determine the transcriptional effects exerted in the spleen, kidney, and gut after a single oral administration of the bacteria. Our results showed that B. subtilis ABP1 had the capacity to modulate the proliferation, IgM secreting capacity and MHC II surface expression of splenic B cells. Finally, we confirmed that this strain also induced the transcription of genes involved in inflammation, antimicrobial genes, and genes involved in T cell responses upon a single oral administration. Our results provide valuable information regarding how B. subtilis modulates the immune response of rainbow trout, pointing to the usefulness of the ABP1 strain to design novel oral vaccination strategies for aquaculture.

Probiotic Characteristics and Antimicrobial Potential of a Native Bacillus subtilis Strain Fa17.2 Rescued from Wild Bromelia sp. Flowers

In the present study, we identified the Bacillus subtilis strain annotated Fa17.2 isolated from Bromelia flower inflorescences collected from the subtropical humid mesothermal region, Santo Domingo de Los Tsachilas Province, Ecuador. The probiotic capacity and antimicrobial potential against four foodborne pathogens were assessed. The cell culture of Fa17.2 is highly resistant to synthetic gastric acid (pH 2.5, 3.0, and 3.5), bile salts (0.3%), tolerating different sodium chloride concentrations (1, 3, and 5%), and growth conditions (15 °C and 45 °C), suggesting its potential probiotic features. The isolate showed no antibiotic resistance and was considered safe as no hemolysis was detected on sheep blood agar. The optimum medium for bacterial growth and the release of antimicrobial compounds was MRS with 10% glucose. The active components released in the neutralized crude extract (NCE) were insensitive to organic solvents, surfactants, and nonproteolytic enzymes and sensitive to proteolytic enzymes suggesting their proteinaceous nature. The antimicrobial activity was enhanced by heat and maintained active over a wide range of pH (2.0–8.0). Moreover, the crude extract (CE) showed inhibitory activity against several Gram-negative and Gram-positive bacteria. The molecular weight of partially purified precipitated bacteriocin-like substances (BLISs) was about 14 kDa in 20% Tricine-SDS-PAGE. The CE obtained from Fa17.2 inhibits the growth of four foodborne pathogens, Staphylococcus aureus, Escherichia coli, Kosaconia cowanii, and Shigella dysenteriae, which implies its potential as an antimicrobial producer strain.

Probiotic Potential of Bacillus licheniformis and Bacillus pumilus Isolated from Tibetan Yaks, China

Yak (Bos grunniens) inhabit an oxygen-deficient environment at the altitude of 3000 m on the Tibetan Plateau, with a distinctive gut micro-ecosystem. This study evaluated the probiotic potential and physiological property of Bacillus licheniformis and Bacillus pumilus isolated from the gut of yaks. Four strains, two Bacillus licheniformis (named D1 and D2) and two Bacillus pumilus (named X1 and X2), were isolated and identified by 16S rRNA sequencing. All strains had potential antibacterial ability against three indicator pathogens: Escherichia coli C83902, Staphylococcus aureus BNCC186335, and Salmonella enteritidis NTNC13349. The antioxidant activity test showed that D2 sample showed the highest antioxidant activity. Furthermore, all four strains had a higher hydrophobicity, auto-aggregation, acid tolerance, bile tolerance, and antibiotic sensitivity, which all contribute to their survival in the gastrointestinal tract and clinical utility. The animal experimentation (40 KM mice, equally divided into five groups of eight mice each) showed that the strain supplementation not only increased daily weight gain and reduced feed conversion ratio, but also increased the length of the jejunum villi and the value of the V/C (Villi/Crypt). In conclusion, this is the first study demonstrated the probiotic potential of Bacillus licheniformis and Bacillus pumilus isolated from yaks, providing a theoretical basis for the clinical application and development of new feed additives.

Antibiotic-active heterotrophic Firmicutes sheltered in seaweeds: can they add new dimensions to future antimicrobial agents?

Appearance of drug-resistant microorganisms prompted researchers to unravel new environments for development of novel antimicrobial agents. Culture-supported analysis of heterotrophic bacteria associated with seaweeds yielded 152 strains, in that larger share of the isolates was embodied by Bacillus atrophaeus SHB2097 (54%), B. velezensis SHB2098 (24%), B. subtilis SHB2099 (12%), and B. amyloliquefaciens SHB20910 (10%). One of the most active strains characterized as B. atrophaeus SHB2097 (MW821482) with an inhibition zone more than 30 mm on spot-over-lawn experiment, was isolated from a seaweed Sargassum wightii, was selected for bioprospecting studies. Significant antibacterial potential was displayed by bacterial organic extract against vancomycin-resistant Enterococcus faecalis, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and Klebsiella pneumonia with minimum inhibitory concentration 6.25 µg/mL and comparable to the antibiotics ampicillin and chloramphenicol. The genes of type 1 pks (MZ222383, 700 bp) and hybrid nrps/pks (MZ222389, 1000-1400 bp) of B. atrophaeus MW821482 could be amplified. The bacterium displayed susceptibility to the commercially available antibiotic agents, and was negative for the pore-forming non-hemolytic hemolysin BL (hbl) and enterotoxin (nhe) genes, and therefore, was not pathogenic. The bacterium was found to possess genes (1000-1400 bp) involved in the biosynthesis of siderophore-class of compounds (MZ222387 and MZ222388) that showed 99% of similarity in BLAST search, and showed production of siderophore. Noteworthy antibacterial activities against clinically important pathogenic bacteria in conjunction with occurrence of genes coding for antimicrobial metabolites inferred that the marine heterotrophic bacterium B. atrophaeus SHB2097 could be used for the development of antibacterial agents against the emerging antibiotic resistance.

In vitro modulation of gilthead seabream (Sparus aurata L.) leukocytes by Bacillus spp. extracellular molecules upon bacterial challenge

Stimulation of the fish immune system using immunostimulants is an environmentally friendly strategy to minimize bacterial outbreaks in aquaculture. Different biological and synthetic immunostimulants can enhance non-specific innate immune responses by directly activating immune cells. An example are Bacillus spp., known for their immunostimulatory effects, although the exact mechanisms by which Bacillus spp. offer protection against diseases remains to be elucidated. Furthermore, most studies have focused on Bacillus spp. cells, while the immunostimulant effect of their extracellular metabolome, known to harbour biologically important metabolites, including antimicrobial molecules, has been scarcely evaluated. Here, we evaluated the in vitro immune-modulatory properties of extracellular extracts of three Bacillus spp. strains (B. subtilis FI314, B. vezelensis FI436 and B. pumilus FI464), previously isolated from fish-guts and characterized for their in vitro and in vivo antimicrobial activity against a wide range of fish pathogens. Bacillus spp. extracellular extracts did not affect immune cells viability, but remarkably increased pathogens' phagocytosis when seabream head-kidney leukocytes were challenged with Vibrio anguillarum and Edwardsiella tarda. All extracts significantly increased the engulfment of bacterial pathogens 1 h post-infection. Cells stimulated with the extracellular extracts showed an up-regulation of the expression of immune-relevant genes associated with inflammation, including IL-1β, IL-6, and COX-2. In cells challenged with E. tarda, FI314 extracellular extract significantly increased the expression of IL-1β, IL-6, and COX-2, while FI436 and FI464 significantly increased IL-6 expression. The results of this study revealed that the extracellular molecules from Bacillus spp. fish isolates improved the in vitro response of gilthead seabream immune cells and are thus promising candidates to act as immunostimulants, helping fish fight diseases.

Comparative Study of Bacillus amyloliquefaciens X030 on the Intestinal Flora and Antibacterial Activity Against Aeromonas of Grass Carp

Beneficial microorganisms to control bacterial diseases has been widely used in aquaculture, Bacillus amyloliquefaciens (BaX030) as a probiotic feed additive was a commonly biological control method. Added sucrose promoted the growth of BaX030, and the yield of its antibacterial substance macrolactin A was enhanced by 1.46-fold. A total of 2055 proteins were screened through proteomics, with 143 upregulated and 307 downregulated. Differential protein expression analysis and qRT-PCR verification showed that the pentose phosphate pathway and the fatty acid synthesis pathway were upregulated, thereby providing sufficient energy and precursors for the synthesis of macrolactin A. The influence of some potential regulatory factors (SecG, LiaI, MecG and ComG) on macrolactin A was discovered. After grass carp were fed with BaX030, the abundance of probiotics (Fusobacterium, Proteobacteria, Gemmobacter) were higher than the control group, and the abundance of potential pathogenic bacteria (Planctomycetes, Aeromonas) were significantly lower than the control group. The cell and challenge experiments showed that BaX030 can significantly increase the expression of C3 and IL8 in the liver and kidney, which decreases the risk of immune organ disease. Moreover, BaX030 effectively reduced the mortality of grass carp. The results revealed that BaX030 can significantly improve the structure of the intestinal flora, enhance immunity and it is beneficial to the control of grass carp Aeromonas.

Analysis of the probiotic activity of Bacillus velezensis RT-26 strain isolated from reindeer rumen by whole-genome sequencing

The paper analyses the properties of Bacillus velezensis RT-26, a probiotic strain isolated from reindeer rumen, which has high activity towards fiber degradation, against bacterial and fungal pathogens. The analysis was performed using whole-genome sequencing of the strain using the Illumina platform. The study revealed that strain RT-26 possessed a complete set of metabolic pathways, including glycolysis, the tricarboxylic acid cycle, and the pentose phosphate pathway. 411 genes were involved in carbohydrate metabolism in the strain genome, 229 genes were related to vitamin and coenzyme metabolism, 149 genes were involved in fatty acid metabolism. The synthesis pathways of various amino acids, most B vitamins (thiamine, riboflavin, nicotiamide, vitamin B5) were identified in the genome. A complete pathway for synthesis of the dipeptide antibiotic bacilisin was detected in the strain. In addition, the strain is capable of synthesizing class A beta-lactamase. No genes responsible for the degradation of mycotoxins and xenobiotics were detected in the genome of the strain studied. A number of glycosyl hydrolase families were detected in the strain genome: GH 1, 3, 4, 5, 6, 11, 13, 16, 18, 20, 23, 26, 28, 30, 32, 43, 46, 51, 53, 68, 68, 73, 101, 109, 126. Carbohydrate-binding proteins were of the SVM 50 family. Glycosyltransferases were of GT 1, 2, 4, 8, 26, 28, 30, 51, 83 families. In the genome of Bacillus velezensis strain RT-26, cellulases related to families GH 5, 6, 26, 51, chitinases related to families GH 18 and 23, and xylanases related to families GH 1, 3, 4, 16, 30, 43 were found. Thus, strain B. velezensis RT-26 has several phenotypically and genotypically proven properties that can characterize it as a good probiotic microorganism.