A New Isolate of Pediococcus pentosaceus (SL001) With Antibacterial Activity Against Fish Pathogens and Potency in Facilitating the Immunity and Growth Performance of Grass Carps

Fish gut-derived probiotic Pediococcus pentosaceus alleviates gossypol-induced intestinal inflammation by inhibiting NLRC3/NF-κB/IL-1β signal pathway in Nile tilapia

Cottonseed meal (CSM) and cottonseed protein concentrate (CPC) serve as protein alternatives to fish meal and soybean meal in the feed industry. However, the presence of gossypol residue in CSM and CPC can potentially trigger severe intestinal inflammation, thereby restricting the widespread utilization of these two protein sources. Probiotics are widely used to prevent or alleviate intestinal inflammation, but their efficacy in protecting fish against gossypol-induced enteritis remains uncertain. Here, the protective effect of Pediococcus pentosaceus, a strain isolated from the gut of Nile tilapia (Oreochromis niloticus), was evaluated. Three diets, control diet (CON), gossypol diet (GOS) and GOS supplemented with P. pentosaceus YC diet (GP), were used to feed Nile tilapia for 10 weeks. After the feeding trial, P. pentosaceus YC reduced the activity of myeloperoxidase (MPO) in the proximal intestine (PI) and distal intestine (DI). Following a 7-day exposure to Aeromonas hydrophila, the addition of P. pentosaceus YC was found to increase the survival rate of the fish. P. pentosaceus YC significantly inhibited the oxidative stress caused by gossypol, which was evidenced by lower reactive oxygen species (ROS) and malondialdehyde (MDA), as well as higher activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in PI and DI. Addition of P. pentosaceus YC significantly inhibited enteritis, with the lower expression of pro-inflammatory cytokines (il-1β, il-6, il-8) and higher expression of anti-inflammatory cytokines tgf-β. RNA-seq analysis indicated that P. pentosaceus YC supplementation significantly inhibited nlrc3 and promoted nf-κb expression in PI and DI, and the siRNA interference experiment in vivo demonstrated that intestinal inflammation was mediated by NLRC3/NF-κB/IL-1β signaling pathway. Fecal bacteria transplantation experiment demonstrated that gut microbiota mediated the protective effect of P. pentosaceus YC. These findings offer valuable insights into the application of P. pentosaceus YC for alleviating gossypol-induced intestinal inflammation in fish.

Influence of Pediococcus pentosaceus GT001 on Performance, Meat Quality, Immune Function, Antioxidant and Cecum Microbial in Broiler Chickens Challenged by Salmonella typhimurium

This study evaluated the effects of Pediococcus pentosaceus GT001 on Salmonella typhimurium (S. typhimurium)-challenged broiler chickens. Two hundred Ross 708 broiler day-old chicks with comparable weight were distributed at random into four treatments with five replicates and ten chicks per replicate. The following were the treatment groups: (B) basal diet (control); (B + S) basal diet and birds were challenged with S. typhimurium at 1.0 × 107 cfu/g; (B + P) basal diet + Pediococcus pentosaceus GT001 at 4.0 × 108 cfu/g; (B + P + S) basal diet + P. pentosaceus GT001 at 4.0 × 108 cfu/g and birds were challenged with S. typhimurium at 1.0 × 107 cfu/g. There was a significant reduction (p < 0.05) in the body weight of the Salmonella-infected birds compared to the other treatment groups. However, the FCRs of the broilers were comparable among the different treatment groups (p > 0.05). The lipid profile and liver function indices measured were significantly enhanced in the P. pentosaceus GT001-supplemented groups (B + P and B + P + S) compared to the group that was Salmonella-challenged (p < 0.05) but were similar to those in the control group. The serum antioxidant activities, such as the T-AOC, SOD, CAT, GHS-Px and MDA, were significantly improved in the P. pentosaceus GT001-supplemented groups (B + P and B + P + S) (p < 0.05). The MDA was similar in the B + P and B + P + S groups, but both were significantly lower than the control and the Salmonella groups. The administration of P. pentosaceus GT001 enhanced the lipase and amylase levels in both the serum and intestine of the broilers (p < 0.05). The immunoglobin (IgA, IgG, IgM) and cytokine (IL-10 and IL-6) levels in the serum were significantly higher in the B, B + P and B + P + S treatment groups (p < 0.05). The immune-related organs (bursa and spleen) were significantly influenced in the birds fed with P. pentosaceus GT001. No significant variation was noted among all the dietary treatments in terms of the measured meat quality indices. The small intestinal digesta content of the Salmonella load was below a detectable range after 14 days of infection (p < 0.05). No significant differences were observed among the different treatment groups in terms of the breast pH, drip loss and meat color (p > 0.05). The inclusion of P. pentosaceus GT001 also modified the community structure in the cecum. This indicates that it has health benefits and could be incorporated in the broiler diet.

An off-the-shelf small extracellular vesicle nanomedicine for tumor targeting therapy

Small extracellular vesicles (sEVs) have shown excellent prospects as drug delivery systems for cancer therapy. However, the inherent non-targeting and short blood circulation characteristics severely restrict their practical applications as a delivery system. In addition, post-encapsulating drugs into sEVs also remains challenging. Here, we constructed an engineered cell line that secreted multifunctional sEVs (termed NBsEV204) with 7D12 (an anti-EGFR nanobody) and hCD47 decorations on their surface, as well as high levels of miR-204-5p encapsulation. NBsEV204 exhibited extended blood circulation and improved macrophage-mediated phagocytosis of tumor cells by blocking CD47 signaling. Importantly, NBsEV204 specifically targeted EGFR+ tumor cells and showed robust tumor-suppressive effects both in vitro and in vivo. Overall, this study provides a convenient and feasible method to produce off-the-shelf anticancer sEV nanomedicine, which exhibits tremendous potential for clinical translation.

Preparation of Phillygenin-Hyaluronic acid composite milk-derived exosomes and its anti-hepatic fibrosis effect

Liver fibrosis remains a serious problem affecting the health of millions of people worldwide. Hepatic stellate cells (HSCs) are the main effector cells in liver fibrosis and their activation could lead to extracellular matrix deposition, which may aggravate the development of liver fibrosis and inflammation. Previous studies have reported the potential of Phillygenin (PHI) as a hepatoprotective agent to inhibit HSCs activation and fibrosis development. However, the poor water solubility of PHI hinders its clinical application as a potential anti-liver fibrosis therapy. Milk-derived exosomes (mEXO) serve as scalable nanocarriers for delivering chemotherapeutic agents due to their excellent biocompatibility. Here, we developed a PHI-Hyaluronic acid (HA) composite mEXO (PHI-HA-mEXO) drug delivery system, in which DSPE-PEG2000-HA was conjugated to the surface of mEXO to prepare HA-mEXO, and PHI was encapsulated into HA-mEXO to form PHI-HA-mEXO. As a specific receptor for HA, CD44 is frequently over-expressed during liver fibrosis and highly expressed on the surface of activated HSCs (aHSCs). PHI-HA-mEXO can bind to CD44 and enter aHSCs through endocytosis and release PHI. PHI-HA-mEXO drug delivery system can significantly induce aHSCs death without affecting quiescent HSCs (qHSCs) and hepatocytes. Furthermore, we carried out in vitro and in vivo experiments and found that PHI-HA-mEXO could alleviate liver fibrosis through aHSCs-targeted mechanism. In conclusion, the favorable biosafety and superior anti-hepatic fibrosis effects suggest a promising potential of PHI-HA-mEXO in the treatment of hepatic fibrosis. However, detailed pharmokinetics and dose-responsive experiments of PHI-HA-mEXO and the mechanism of mEXO loading drugs are still required before PHI-HA-mEXO can be applied clinically.

Microbiome Interconnectedness throughout Environments with Major Consequences for Healthy People and a Healthy Planet

Microbiomes have highly important roles for ecosystem functioning and carry out key functions that support planetary health, including nutrient cycling, climate regulation, and water filtration. Microbiomes are also intimately associated with complex multicellular organisms such as humans, other animals, plants, and insects and perform crucial roles for the health of their hosts. Although we are starting to understand that microbiomes in different systems are interconnected, there is still a poor understanding of microbiome transfer and connectivity. In this review we show how microbiomes are connected within and transferred between different habitats and discuss the functional consequences of these connections. Microbiome transfer occurs between and within abiotic (e.g., air, soil, and water) and biotic environments, and can either be mediated through different vectors (e.g., insects or food) or direct interactions. Such transfer processes may also include the transmission of pathogens or antibiotic resistance genes. However, here, we highlight the fact that microbiome transmission can have positive effects on planetary and human health, where transmitted microorganisms potentially providing novel functions may be important for the adaptation of ecosystems.

Histomorphological Changes in Fish Gut in Response to Prebiotics and Probiotics Treatment to Improve Their Health Status: A Review

The gastrointestinal tract (GIT) promotes the digestion and absorption of feeds, in addition to the excretion of waste products of digestion. In fish, the GIT is divided into four regions, the headgut, foregut, midgut, and hindgut, to which glands and lymphoid tissues are associated to release digestive enzymes and molecules involved in the immune response and control of host-pathogens. The GIT is inhabited by different species of resident microorganisms, the microbiota, which have co-evolved with the host in a symbiotic relationship and are responsible for metabolic benefits and counteracting pathogen infection. There is a strict connection between a fish's gut microbiota and its health status. This review focuses on the modulation of fish microbiota by feed additives based on prebiotics and probiotics as a feasible strategy to improve fish health status and gut efficiency, mitigate emerging diseases, and maximize rearing and growth performance. Furthermore, the use of histological assays as a valid tool for fish welfare assessment is also discussed, and insights on nutrient absorptive capacity and responsiveness to pathogens in fish by gut morphological endpoints are provided. Overall, the literature reviewed emphasizes the complex interactions between microorganisms and host fish, shedding light on the beneficial use of prebiotics and probiotics in the aquaculture sector, with the potential to provide directions for future research.

Diversity analysis of hilsa (Tenualosa ilisha) gut microbiota using culture-dependent and culture-independent approaches

AIMS

The bacterial communities associated with the gastrointestinal (GI) tract are primarily involved in digestion, physiology, and the immune response against pathogenic bacteria for the overall development and health of the host. Hilsa shad (Tenualosa ilisha), a tropical anadromous fish, found predominantly in Bangladesh and India, has so far been poorly investigated for its gut bacterial communities. In this study, both culture-based and metagenomic approaches were used to detect intestinal isolates of hilsa, captured from both freshwater and seawater to investigate the community structure of intestinal microbiota.

METHODS AND RESULTS

Culture-dependent approach allowed to isolate a total of 23 distinct bacterial species comprising 16 Gram-negative, and 7 Gram-positive isolates, where Proteobacteria and Firmicutes were identified as the two most dominant phyla. While metagenomic approach explored a wide range of important GI bacteria, primarily dominated by Proteobacteria, Firmicutes, and Bacteroidetes, with Proteobacteria and Firmicutes, being the most abundant in freshwater and seawater samples, respectively.

CONCLUSIONS

A combination of these approaches provided the differential GI-associated bacterial diversity in freshwater and seawater hilsa with the prediction of overall functional potential.

IMPACT STATEMENT

The study explored the diversity of gut microbiota in hilsa, one of the most preferred nutritious dietary fish, captured from freshwater and seawater habitats, which may encourage to comprehend the composition of the gut microbiome in relation to the migratory behavior and polyunsaturated fatty acid profile of anadromous fish in general.

Dietary administration of a postbiotic, heat-killed Pediococcus pentosaceus PP4012 enhances growth performance, immune response and modulates intestinal microbiota of white shrimp, Penaeus vannamei

The efficacy of postbiotics on the immune-related gene expression and gut microbiota of white shrimp (Penaeus vannamei) remains unexplored. A commercial heat-killed postbiotic Pediococcus pentosaceus PP4012 was used to evaluate the growth performance, intestinal morphology, immunological status, and microbial community of white shrimp after dietary administration in this study. White shrimp (0.040 ± 0.003 g) were divided into three treatments; a control, inanimate P. pentosaceus (10⁵ CFU g feed^-1) at low concentration (IPL) and inanimate P. pentosaceus (10⁶ CFU g feed^-1) at high concentrations (IPH). The diets of IPL and IPH significantly increased final weight, specific growth rate and production compared to the control group. Shrimp fed with IPL and IPH significantly utilized feed more efficiently than those fed the control diet. The IPH treatment significantly lowered the cumulative mortality rate compared to the control and IPL diet following Vibrio parahaemolyticus infection. No significant difference was observed for Vibrio-like and lactic acid bacteria in intestine of shrimp fed with the control diet and the experimental diets. Adding inanimate P. pentosaceus significantly improved immune responses such as lysozyme and phagocytic activity compared to the control group. However, the total hemocyte count, phenoloxidase activity, respiratory burst, and superoxide dismutase were not significantly different among treatments. The immune-related genes alf, pen3a, and pen4 expression were significantly higher in shrimp fed IPL diet compared with control and IPH. Taxonomic identification of bacterial genera in all dietary groups belonged to two predominant phyla, Proteobacteria and Bacteroidota. An abundance of Photobacterium, Motilimonas, Litorilituus, and Firmicutes bacterium ZOR0006 were identified in the intestine of shrimp fed postbiotic diets. Unique microbes such as Cohaesibacter was discovered in the shrimp fed IPL while Candidatus Campbellbacteria, uncultured Verrucomicrobium DEV114 and Paenalcaligenes were discovered in the intestines of shrimp fed IPH diet. Collectively, these data suggest that including heat-killed P. pentosaceus, particularly IPH, can enhance growth performance, promote microbial diversity, elevate immune responses, and increase shrimp's resistance to V. parahaemolyticus.

Functional properties of lactic acid bacteria isolated from Tilapia (Oreochromis niloticus) in Ivory Coast

BACKGROUND

Probiotics have recently been applied in aquaculture as eco-friendly alternatives to antibiotics to improve fish health, simultaneously with the increase of production parameters. The present study aimed to investigate the functional potential of lactic acid bacteria (LAB) isolated from the gut of Tilapia (Oreochromis niloticus) originating from the aquaculture farm of Oceanologic Research Center in Ivory Coast.

RESULTS

Twelve LAB strains were identified by 16 S rDNA gene sequence homology analysis belonging to two genera Pediococcus (P. acidilactici and P. pentosaceus) and Lactobacillus (L. plantarum) with a predominance of P. acidilactici. Several aspects including functional, storage, and safety characteristics were taken into consideration in the selection process of the native LAB isolates as potential probiotics. All LAB isolates showed high antagonistic activity against bacterial pathogens like Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis, and Staphylococcus aureus. In addition, the LAB isolates exhibited different degrees of cell surface hydrophobicity in the presence of hexane, xylene, and chloroform as solvents and a good ability to form biofilm. The strong antioxidant activity expressed through the DPPH scavenging capacity of LAB intact cells and their cell-free supernatants was detected. LAB strains survived between 34.18% and 49.9% when exposed to low pH (1.5) and pepsin for 3 h. In presence of 0.3% bile salts, the growth rate ranged from 0.92 to 21.46%. Antibiotic susceptibility pattern of LAB isolates showed sensitivity or intermediate resistance to amoxicillin, cephalothin, chloramphenicol, imipenem, kanamycin, penicillin, rifampicin, streptomycin, tetracycline and resistance to oxacillin, gentamicin, and ciprofloxacin. No significant difference in antibiotic susceptibility pattern was observed between P. acidilactici and P. pentosaceus strains. The non-hemolytic activity was detected. Following the analysis of the enzyme profile, the ability of LAB isolates to produce either lipase or β-galactosidase or both enzymes was highlighted. Furthermore, the efficacy of cryoprotective agents was proved to be isolate-dependent, with LAB isolates having a high affinity for D-sorbitol and sucrose.

CONCLUSION

The explored LAB strains inhibited the growth of pathogens and survived after exposure to simulated gastrointestinal tract conditions. The safety and preservative properties are desirable attributes of these new probiotic strains hence recommended for future food and feed applications.

Effects of dietary Cetobacterium somerae on the intestinal health, immune parameters and resistance against Nocardia seriolae of largemouth bass, Micropterus salmoides

Largemouth bass (Micropterus salmoides), one of the most important freshwater commercial fish species has been widely cultivated in China. In recent years, the nocardiosis caused by Nocardia seriolae has greatly damaged the M. salmoides industry and there is no effective treatment at present. Currently, Cetobacterium somerae, the predominant bacteria in the gut of many freshwater fishes has been reported to be associated with fish health. However, whether the native C. somerae could protect the host from N. seriolae is unclear. In this study, M. salmoides were fed with three different diets, including control diet (CD), low C. somerae diet (10⁶ CFU/g as LD) and high C. somerae diet (10⁸ CFU/g as HD). After 8-week feeding, growth performance, gut health index, serum enzyme activities and the expression of inflammation-related genes were tested. Results showed that the LD and HD diets had no adverse effects on the growth performance. Moreover, dietary HD enhanced gut barrier and reduced intestinal ROS and ORP, as well as increased serum enzyme activities including ACP, AKP, SOD and LZM compared to the CD group. In addition, the HD diet significantly up-regulated the expression of TNF-α, IL8, IL-1β and IL15, while down-regulating the expression of TGF-β1 and IL10 in kidney. Moreover, the expression of antibacterial genes was significantly increased in HD group after being challenged by N. seriolae. And the fish fed HD diet exhibited higher survival rate (57.5%) than that in CD (37.5%) and LD groups (42.5%). To summarize, our study demonstrates that dietary HD can enhance gut health, improve immune response and strengthen pathogen resistance, suggesting that C. somerae is a potential probiotic for defending against N. seriolae infection in M. salmoides.

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.

Screening of new Paenibacillus polymyxa S3 and its disease resistance of grass carp (Ctenopharyngodon idellus)

A new strain of Paenibacillus polymyxa S3 with antagonistic effects on 11 major fish pathogens (especially Aeromonas hydrophila), but had no toxicity to grass carp, was screened from the sediment of fishponds. In vivo colonization studies showed that strain S3 could be colonized and distributed in the gill and abdomen of the grass carp. Bioassay results showed that the weight growth rate of grass carp in the strain S3 oral group (16.01%) and strain S3 immersion group (16.44%) was significantly higher than those of the control group (8.61%). At the same time, the activities of ACP, AKP, CAT and GSH-Px in the serum of grass carp in oral and immersion groups were significantly higher than those of the control group. In addition, the treatment with strain S3 could significantly upregulate the expression of the antioxidant-related genes and immune-related genes Keap1, Nrf2, C3, LZM, IgM, TLR-4 and MyD-88 in grass carp tissues. The challenge test showed that strain S3 treatment significantly increased the survival rate of grass carp infected with Aeromonas hydrophila. Whole genome sequencing analysis showed that strain S3 had 16 active metabolite gene clusters, indicating that it had abundant gene resources, which provided important support for its development for fish microecological preparations. In summary, a new strain of Paenibacillus polymyxa S3 with antibacterial activity against a variety of fish pathogens was screened in this study and its probiotic function was evaluated, proving its potential value in fisheries.

Effect of Probiotics on Tenebrio molitor Larval Development and Resistance against the Fungal Pathogen Metarhizium brunneum

In recent years, the yellow mealworm (Tenebrio molitor L.) has demonstrated its potential as a mass-produced edible insect for food and feed. However, challenges brought on by pathogens in intensive production systems are unavoidable and require the development of new solutions. One potential solution is the supplementation of probiotics in the insect's diet to obtain the double benefits of improved growth and enhanced immune response. The aim of this study was to evaluate the effects of diet-based probiotic supplementation on T. molitor larval survival, growth, and resistance against a fungal pathogen. Three probiotic strains, namely Pediococcus pentosacceus KVL-B19-01 isolated from T. molitor and two commercialized strains for traditional livestock, Enterococcus faecium 669 and Bacillus subtilis 597, were tested. Additionally, when larvae were 9 weeks old, a pathogen challenge experiment was conducted with the fungus Metarhizium brunneum. Results showed that both P. pentosaceus and E. faecium improved larval growth and larval survival following fungal exposure compared to the non-supplemented control diet. Since B. subtilis did not improve larval performance in terms of either development or protection against M. brunneum, this study suggests the need for further research and evaluation of probiotic strains and their modes of action when considered as a supplement in T. molitor's diet.

Isolation, Characterization, and Effect on Biofilm Formation of Bacteriocin Produced by Lactococcus lactis F01 Isolated from Cyprinus carpio and Application for Biopreservation of Fish Sausage

The aim of this work was the screening of bacteriocin-producing LABs isolated from fish, the selection of promising/prominent strain(s), the characterization of the bacteriocin produced, and the evaluation of its potential to be used as biopreservative(s). Amplification and sequencing of the 16S rRNA gene of the bacteriocin-producing strain was performed. Then a partial purification of the produced bacteriocin, using a combination of ammonium sulfate and chloroform-methanol precipitation, was done. Its molecular weight was determined by SDS-PAGE. In addition, the action spectrum, the hemolysis test, and its ability to inhibit biofilm formation were analyzed. A total of 88 isolates of lactic acid bacteria (LAB) including one bacteriocin producer, which was identified as Lactococcus lactis F01, were collected. The bacteriocin was partially purified with an estimated yield of 40%. Regarding the SDS-PAGE profile, the secreted bacteriocin has molecular weight of about 3.5 kDa and was identified as class I bacteriocin. The antimicrobial test showed that the bacteriocin inhibits pathogenic and/or spoilage bacteria, 10 Gram-positive and 16 Gram-negative bacterial species. Moreover, it can inhibit biofilm formation from 1.3% (Escherichia coli) to 63.92% (Pseudomonas aeruginosa ATCC15692) depending on the strain. The hemolytic activity of novel bacteriocin was observed at the concentration of 10 μg/ml of bacteriocin crude extract, which was $0.7\pm 0.0029\%$ . In addition, it exhibited good thermal and pH stability with retained antibacterial activity of 85.25% after treatment at 121°C for 20 min, as well as at a pH range between 2.0 and 10.0. Moreover, this bacteriocin showed the ability to inhibit the growth of bacterial culture load in fish sausage stored at 8°C for 28 days. Considering the results obtained, bacteriocin could be potentially exploited as an alternative to chemical preservatives or as a substitute for antibiotics.

Dietary supplementation with Pediococcus pentosaceus enhances the innate immune response in and promotes growth of Litopenaeus vannamei shrimp

To reach the sustainable development goals on health management in Litopenaeus vannamei shrimp culture, Pediococcus pentosaceus AB01 was supplemented in shrimp diet. In this study, the control diet and three experimental diets containing P. pentosaceus AB01 (10⁸ , 10⁹ , 10¹⁰  CFU/g) were separately introduced to L. vannamei for a 28 days feeding trial. After the feeding trial, percent weight gain, feeding efficiency, and feed conversion ratio (FCR) were significantly elevated in L. vannamei administered with P. pentosaceus AB01 at 10⁹ and 10¹⁰ colony-forming unit (CFU)/g. Protease, amylase, and trypsin were found at higher levels in the probiotic-supplied groups. The feeding of shrimps with P. pentosaceus AB01 significantly increased innate immune response and levels of related biochemical parameters in the haemolymph. After the white spot syndrome virus (WSSV) challenge, supplementation of P. pentosaceus AB01 had significant positive effects (p < .05) on survival rate, compared to that of the control diet. The higher resistance of L. vannamei to WSSV might have been due to alterations in the gut microbiome composition and upregulation of the Toll-Like Receptor (TLR) signalling pathway. Hence, P. pentosaceus AB01 may be a promising alternative feed to promote growth rate, modulate microbiota composition, and enhance immunity in L. vannamei shrimp.

Enhancement of liver mitochondrial complex I and energy metabolism induced by enteritis: The key role of gut microbiota derived endotoxins

Inflammation is an energy-intensive process and the liver is a key organ in energy regulation. Since the intestine and liver exchange nutrients and metabolites, enteritis can affect the liver. To investigate the correlation between enteritis and liver metabolism, we developed an intestinal inflammation model with concentration-dependent 2,4,6-trinitrobenzene sulfonic acid (TNBS) in gibel carp (Carassius gibelio). The results showed the dysregulation of intestinal tight junction, increased permeability of the gut barrier, and apoptosis of epithelial cells during the development of enteritis. The liver metabolome was analyzed by LC-MS and the live respiration was determined using Oxygraph-2k. The results showed that glycolysis, the TCA cycle and pyrimidine metabolism were affected by intestinal inflammation. In particular, the activity of hepatic mitochondrial respiratory chain complex I was significantly increased. Structure and abundance changes of gut microbiota were analyzed by 16S rRNA sequencing analysis. Pathogenic bacteria in the intestine, as well as plasma LPS, increased significantly. Using a liver cell line, we verified that the dysfunctional metabolism of the liver is related to the dislocation of LPS. All results imply the existence of a connection between enteritis and liver metabolism in gibel carp, and the gut microbiome plays a critical role in this process.

Heat Stress Decreases Intestinal Physiological Function and Facilitates the Proliferation of Harmful Intestinal Microbiota in Sturgeons

Heat is a common source of stress in aquatic environments and can alter the physiological and metabolic functions of aquatic animals, especially their intestinal function. Here, the effects of heat stress on the structure and function of the intestine and the characteristics of the intestinal microbiota were studied in sturgeon (Acipenser baerii ♀ × Acipenser schrenckii ♂ hybrid F1). Sturgeons were exposed to sub-extreme (24°C) and extreme (28°C) high water temperatures for 12 days. The heat stress caused systemic damage to the intestine of sturgeons, which displayed severe enteritis in the valve intestine. The microbial diversity analysis showed that heat stress led to the disorder in intestinal microbiota, manifesting as an explosive increase in the abundance of thermophilic intestinal pathogens such as Plesiomonas, Cetobacterium, and Aeromonas and causing physiological dysfunction in the sturgeons. The disorder was followed by significant inhibition of intestinal digestion with reduced chymotrypsin, α-amylase, and lipase activities in the valve intestine and of antioxidant function with reduced peroxidase (POD) and catalase (CAT) activities. Simultaneously, heat stress reduced the thermal tolerance of sturgeons by reducing Grp75 expression and damaged the valve intestine’s repair ability with increased Tgf-β expression. The results confirmed that heat stress damaged the sturgeon intestines obviously and disturbed the intestinal microbiota, resulting in serious physiological dysfunction. The present study investigated the mechanism of the effect of heat stress on the sturgeon intestine and will help develop strategies to improve the resistance to thermal stress for wild and cultured sturgeons.

Pediococcus pentosaceus: Screening and Application as Probiotics in Food Processing

Lactic acid bacteria (LAB) are vital probiotics in the food processing industry, which are widely spread in food additives and products, such as meat, milk, and vegetables. Pediococcus pentosaceus (P. pentosaceus), as a kind of LAB, has numerous probiotic effects, mainly including antioxidant, cholesterol-lowering, and immune effects. Recently, the applications in the probiotic- fermentation products have attracted progressively more attentions. However, it is necessary to screen P. pentosaceus with abundant functions from diverse sources due to the limitation about the source and species of P. pentosaceus. This review summarized the screening methods of P. pentosaceus and the exploration methods of probiotic functions in combination with the case study. The screening methods included primary screening and rescreening including gastric acidity resistance, bile resistance, adhesion, antibacterial effects, etc. The application and development prospects of P. pentosaceus were described in detail, and the shortcomings in the practical application of P. pentosaceus were evaluated to make better application of P. pentosaceus in the future.

Pediococcus pentosaceus Enhances Host Resistance Against Pathogen by Increasing IL-1β Production: Understanding Probiotic Effectiveness and Administration Duration

Probiotic administration is a potential strategy against enteric pathogen infection in either clinical treatment or animal nutrition industry, but the administration duration of probiotics varied and the underlying mechanisms remain unclear. A strain (YC) affiliated to Pediococcus pentosaceus, a commonly used probiotic, was isolated from fish gut and the potential role of YC against Aeromonas hydrophila was detected in zebrafish. We found that 3- or 4-week YC administration (YC3W or YC4W) increased the resistance against A. hydrophila while 1- or 2-week treatment (YC1W or YC2W) did not. To determine the possible reason, intestinal microbiota analysis and RNAseq were conducted. The results showed that compared with CON and YC1W, YC4W significantly increased the abundance of short-chain fatty acids (SCFAs) producing bacteria and elevated the gene expression of nlrp3. Higher butyrate content and enhanced expression of IL1β were subsequently found in YC4W. To identify the causal relationship between butyrate and the higher pathogen resistance, different concentrations of sodium butyrate (SB) were supplemented. The results suggested that 10 mmol/kg SB addition mirrored the protective effect of YC4W by increasing the production of IL-1β. Furthermore, the increased IL-1β raised the percentage of intestinal neutrophils, which endued the zebrafish with A. hydrophila resistance. In vivo knockdown of intestinal il1b eliminated the anti-infection effect. Collectively, our data suggested that the molecular mechanism of probiotics determined the administration duration, which is vital for the efficiency of probiotics. Promoting host inflammation by probiotic pretreatment is one potential way for probiotics to provide their protective effects against pathogens.

Pediococcus acidilactici CCFM6432 mitigates chronic stress-induced anxiety and gut microbial abnormalities

The discovery of psychobiotics has improved the therapeutic choices available for clinical mental disorders and shows promise for regulating mental health in people by combining the properties of food and medicine. A Pediococcus acidilactici strain CCFM6432 was previously isolated and its mood-regulating effect was investigated in this study. Viable bacteria were given to chronically stressed mice for five weeks, and then the behavioral, neurobiological, and gut microbial changes were determined. CCFM6432 significantly reduced stress-induced anxiety-like behaviors, mitigated hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, and reversed the abnormal expression of hippocampal phosphorylated CREB and the c-Fos protein. In particular, CCFM6432 improved the gut microbial composition by inhibiting the over-proliferated pathogenic bacteria (e.g., Escherichia-shigella) and promoting beneficial bacteria growth (e.g., Bifidobacterium). Lactic acid, rather than bacteriocin, was further confirmed as the key compound that determined the antimicrobial activity of CCFM6432. Collectively, these results first proved the psychobiotic potential of the Pediococcus acidilactici strain. Ingestion of CCFM6432, or fermented food containing it, may facilitate mental health management in daily life, especially during the COVID-19 pandemic.

Nanobody-Engineered Natural Killer Cell Conjugates for Solid Tumor Adoptive Immunotherapy

Cancer immunotherapy based on natural killer (NK) cells is demonstrated to be a promising strategy. However, NK cells are deficient in ligands that target specific tumors, resulting in limited antitumor efficacy. Here, a glycoengineering approach to imitate the chimeric antigen receptor strategy and decorate NK cells with nanobodies to promote NK-based immunotherapy in solid tumors is proposed. Nanobody 7D12, which specifically recognizes the human epidermal growth factor receptor (EGFR) that is overexpressed on many solid tumors, is coupled to the chemically synthesized DBCO-PEG₄ -GGG-NH₂ by sortase A-mediated ligation to generate DBCO-7D12. The NK92MI cells bearing azide groups are then equipped with DBCO-7D12 via bioorthogonal click chemistry. The resultant 7D12-NK92MI cells exhibit high specificity and affinity for EGFR-overexpressing tumor cells in vitro and in vivo by the 7D12-EGFR interaction, causing increased cytokine secretion to more effectively kill EGFR-positive tumor cells, but not EGFR-negative cancer cells. Importantly, the 7D12-NK92MI cells also show a wide anticancer spectrum and extensive tumor penetration. Furthermore, mouse experiments reveal that 7D12-NK92MI treatment achieves excellent therapeutic efficacy and outstanding safety. The authors' works provide a cell modification strategy using specific protein ligands without genetic manipulation and present a potential novel method for cancer-targeted immunotherapy by NK cells.

Bacteriocins: An Overview of Antimicrobial, Toxicity, and Biosafety Assessment by in vivo Models

The world is facing a significant increase in infections caused by drug-resistant infectious agents. In response, various strategies have been recently explored to treat them, including the development of bacteriocins. Bacteriocins are a group of antimicrobial peptides produced by bacteria, capable of controlling clinically relevant susceptible and drug-resistant bacteria. Bacteriocins have been studied to be able to modify and improve their physicochemical properties, pharmacological effects, and biosafety. This manuscript focuses on the research being developed on the biosafety of bacteriocins, which is a topic that has not been addressed extensively in previous reviews. This work discusses the studies that have tested the effect of bacteriocins against pathogens and assess their toxicity using in vivo models, including murine and other alternative animal models. Thus, this work concludes the urgency to increase and advance the in vivo models that both assess the efficacy of bacteriocins as antimicrobial agents and evaluate possible toxicity and side effects, which are key factors to determine their success as potential therapeutic agents in the fight against infections caused by multidrug-resistant microorganisms.

Mechanisms Used by Probiotics to Confer Pathogen Resistance to Teleost Fish

Probiotics have been defined as live microorganisms that when administered in adequate amounts confer health benefits to the host. The use of probiotics in aquaculture is an attractive bio-friendly method to decrease the impact of infectious diseases, but is still not an extended practice. Although many studies have investigated the systemic and mucosal immunological effects of probiotics, not all of them have established whether they were actually capable of increasing resistance to different types of pathogens, being this the outmost desired goal. In this sense, in the current paper, we have summarized those experiments in which probiotics were shown to provide increased resistance against bacterial, viral or parasitic pathogens. Additionally, we have reviewed what is known for fish probiotics regarding the mechanisms through which they exert positive effects on pathogen resistance, including direct actions on the pathogen, as well as positive effects on the host.

Pediococcus pentosaceus B49 from human colostrum ameliorates constipation in mice

Constipation is a prevalent and burdensome gastrointestinal (GI) disorder that seriously affects the quality of human life. This study evaluated the effects of the P. pentosaceus B49 (from human colostrum) on loperamide (Lop)-induced constipation in mice. Mice were given P. pentosaceus B49 (5 × 109 CFU or 5 × 1010 CFU) by gavage daily for 14 days. The result shows that P. pentosaceus B49 treatment relieved constipation in mice by shortening the defecation time, increasing the GI transit rate and stool production. Compared with the constipation control group, the P. pentosaceus B49-treated groups showed decreased serum levels of inhibitory neurotransmitters (vasoactive intestinal peptide and nitric oxide), increased serum levels of excitatory neurotransmitters (acetylcholinesterase, motilin, and gastrin), and elevated cecal concentration of short chain fatty acids (SCFAs). Analysis of cecal microbiota reveals that P. pentosaceus B49 was colonized in the intestine of constipated mice, and altered the cecal microbiota by increasing beneficial SCFAs-producing bacteria (i.e., Lactobacillus, Ruminococcaceae_UCG-014, and Bacteroidales_S24-7) and decreasing potential pathogenic bacteria (i.e., Staphylococcus and Helicobacter). Moreover, transcriptome analysis of the colon tissue shows that P. pentosaceus B49 partly normalized the expression of genes related to GI peristalsis (i.e., Ache, Chrm2, Slc18a3, Grp, and Vip), water and electrolyte absorption and transport (i.e., Aqp4, Aqp8, and Atp12a), while down-regulating the expression of pro-inflammatory and pro-oncogenic genes (i.e., Lbp, Lgals2, Bcl2, Bcl2l15, Gsdmc2, and Olfm4) in constipated mice. Our findings indicate that P. pentosaceus B49 effectively relieves constipation in mice and is a promising candidate for treating constipation.

ODFM, an omics data resource from microorganisms associated with fermented foods

ODFM is a data management system that integrates comprehensive omics information for microorganisms associated with various fermented foods, additive ingredients, and seasonings (e.g. kimchi, Korean fermented vegetables, fermented seafood, solar salt, soybean paste, vinegar, beer, cheese, sake, and yogurt). The ODFM archives genome, metagenome, metataxonome, and (meta)transcriptome sequences of fermented food-associated bacteria, archaea, eukaryotic microorganisms, and viruses; 131 bacterial, 38 archaeal, and 28 eukaryotic genomes are now available to users. The ODFM provides both the Basic Local Alignment Search Tool search-based local alignment function as well as average nucleotide identity-based genetic relatedness measurement, enabling gene diversity and taxonomic analyses of an input query against the database. Genome sequences and annotation results of microorganisms are directly downloadable, and the microbial strains registered in the archive library will be available from our culture collection of fermented food-associated microorganisms. The ODFM is a comprehensive database that covers the genomes of an entire microbiome within a specific food ecosystem, providing basic information to evaluate microbial isolates as candidate fermentation starters for fermented food production.

Bacteriocins from Lactic Acid Bacteria. A Powerful Alternative as Antimicrobials, Probiotics, and Immunomodulators in Veterinary Medicine

In the search for an alternative treatment to reduce antimicrobial resistance, bacteriocins shine a light on reducing this problem in public and animal health. Bacteriocins are peptides synthesized by bacteria that can inhibit the growth of other bacteria and fungi, parasites, and viruses. Lactic acid bacteria (LAB) are a group of bacteria that produce bacteriocins; their mechanism of action can replace antibiotics and prevent bacterial resistance. In veterinary medicine, LAB and bacteriocins have been used as antimicrobials and probiotics. However, another critical role of bacteriocins is their immunomodulatory effect. This review shows the advances in applying bacteriocins in animal production and veterinary medicine, highlighting their biological roles.

Pediococcus pentosaceus, a future additive or probiotic candidate

Background

Pediococcus pentosaceus, a promising strain of lactic acid bacteria (LAB), is gradually attracting attention, leading to a rapid increase in experimental research. Due to increased demand for practical applications of microbes, the functional and harmless P. pentosaceus might be a worthwhile LAB strain for both the food industry and biological applications.

Results

As an additive, P. pentosaceus improves the taste and nutrition of food, as well as the storage of animal products. Moreover, the antimicrobial abilities of Pediococcus strains are being highlighted. Evidence suggests that bacteriocins or bacteriocin-like substances (BLISs) produced by P. pentosaceus play effective antibacterial roles in the microbial ecosystem. In addition, various strains of P. pentosaceus have been highlighted for probiotic use due to their anti-inflammation, anticancer, antioxidant, detoxification, and lipid-lowering abilities.

Conclusions

Therefore, it is necessary to continue studying P. pentosaceus for further use. Thorough study of several P. pentosaceus strains should clarify the benefits and drawbacks in the future.

Probiotics, lactic acid bacteria and bacilli: interesting supplementation for aquaculture

Probiotics administration in aquafeed is known to increase feed consumption and absorption due to their capacity to release a wide range of digestive enzymes and nutrients which can participate in digestion process and feed utilization, along with the absorption of diet components led to an increase in host's health and well-being. Furthermore, probiotics improve gut maturation, prevention of intestinal disorders, predigestion of antinutrient factors found in the feed ingredients, gut microbiota, disease resistance against pathogens and metabolism. The beneficial immune effects of probiotics are well established in finfish. However, in comparison, similar studies are less abundant in the shellfish. In this review, the discussions will mainly focus on studies reported the last 2 years. In recent studies, native probiotic bacteria were isolated and fed back to their hosts. Although beneficial effects were demonstrated, some studies showed adverse effects when treated with a high concentration. This adverse effect may be due to the imbalance of the gut microbiota caused by the replenished commensal probiotics. Probiotics revealed greatest effect on the shrimp digestive system particularly in the larval and early post-larval stages, and stimulate the production of endogenous enzymes in shrimp and contribute with improved the enzyme activities in the gut, as well as disease resistance.

Comparative analysis and gut bacterial community assemblages of grass carp and crucian carp in new lineages from the Dongting Lake area

Gut microbiota are known to play an important role in health and nutrition of the host and have been attracting an increasing attention. Farming of new lineages of grass carp and crucian carp has been developed rapidly as these species were found to outperform indigenous ones in terms of growth rate and susceptibility to diseases. Despite this rapid development, no studies have addressed the characteristics of their gut microbiota as a potential factor responsible for the improved characteristics. To reveal whether microbiomes of the new lineages are different from indigenous ones, and therefore could be responsible for improved growth features, intestinal microbiota from the new lineages were subjected to high-throughput sequencing. While the phyla Firmicutes, Fusobacteria and Proteobacteria were representing the core bacterial communities that comprised more than 75% in all fish intestinal samples, significant differences were found in the microbial community composition of the new linages versus indigenous fish populations, suggesting the possibility that results in the advantages of enhanced disease resistance and rapid growth for the new fish lineages. Bacterial composition was similar between herbivorous and omnivorous fish. The relative abundance of Bacteroidetes and Actinobacteria was significantly higher in omnivores compared to that of herbivores, whereas Cetobacterium_sp. was abundant in herbivores. We also found that the gut microbiota of freshwater fish in the Dongting lake area was distinct from those of other areas. Network graphs showed the reduced overall connectivity of gut bacteria in indigenous fish, whereas the bacteria of the new fish lineage groups showed hubs with more node degree. A phylogenetic investigation of communities by reconstruction of unobserved states inferred function profile showed several metabolic processes were more active in the new lineages compared to indigenous fish. Our findings suggest that differences in gut bacterial community composition may be an important factor contributing to the rapid growth and high disease resistance of the new fish lineages.

Isolating a new Streptomyces amritsarensis N1-32 against fish pathogens and determining its effects on disease resistance of grass carp

In this study, a Streptomyces strain was isolated from the soil samples of Yanghu Wetland Park in Changsha, Hunan Province. This strain showed excellent antimicrobial activity against 10 fish pathogens, as indicated by the results of the agar-diffusion and oxford cup assays. After 16s rDNA sequencing and physiological & biochemical analyses, it was identified as Streptomyces amritsarensis, namely for S. amritsarensis N1-32. Cytotoxicity test was performed, and the results exhibited that this strain had no toxicity to hepatic L8824 cell line from grass carp liver. The diets supplemented strain N1-32 at concentrations of 1 × 10⁷ cfu/g and 1 × 10⁹ cfu/g was used to feed fish. After 28 days, the expression levels of antioxidant-related genes Nrf2 and Keap1 in the liver and spleen were significantly up-regulated, and the expression of immune-related gene IgM was notably increased in the liver, kidney, head-kidney, and spleen. Toll-like receptor 4 (TLR4) gene expression was up-regulated in the spleen, and TLR4, myeloid differentiation factor 88 (MyD88) gene were up-regulated in the kidney. The survival rate of grass carp was significantly improved after pathogen infection. Whole-genome analysis of N1-32 showed that the strain harbored related genes, capability for producing substances that enhance the immunity of grass carp and inhibit pathogens. A total of 22 gene clusters were identified in the genome, including 5 terpene gene clusters, 4 nonribosomal peptide-synthetase (NRPS) gene clusters and 2 lantipeptide gene clusters. In summary, these results showed that strain N1-32 as a feed additive could regulate grass carp immunity and enhance the resistance of grass carp against fish pathogens.