Screening of intestinal probiotics and the effects of feeding probiotics on the growth, immune, digestive enzyme activity and intestinal flora of Litopenaeus vannamei

The potential influence of microplastics on the microbiome and disease susceptibility in sea turtles

Microplastics (MPs) are particles with sizes of ≤5 mm formed when plastic materials break down. These contaminants are often found in marine environments, making it easy for sea turtles to ingest them and for their microbiome to be exposed. MPs can disrupt microbiome balance, leading to dysbiosis and making organisms more susceptible to diseases. Owing to the significance of these processes, it is crucial to dedicate research to studying the metabolic and genetic analysis of the gut microbiome in sea turtles. The objective of this study was to describe the effects of exposure to MPs on the gut microbiome of sea turtles, based on current knowledge. This review also aimed to explore the potential link between MP exposure and disease susceptibility in these animals. We show that the metabolites produced by the gut microbiome, such as short-chain fatty acids (SCFAs), polyamines, and polysaccharide A, can regulate the expression of host genes. Regulation occurs through various mechanisms, including histone acetylation, DNA methylation, and the modulation of cytokine gene expression. These processes are essential for preserving the integrity of the gut mucosa and enhancing the functionality of immune cells. Exposure to MPs disrupts the gut microbiome and alters gene expression, leading to immune system disturbances in sea turtles. This vulnerability makes turtles more susceptible to opportunistic microorganisms such as chelonid alphaherpesvirus 5 (ChAHV5), which is linked to the development of fibropapillomatosis (FP). Additionally, targeted dietary interventions or the use of live microorganisms such as probiotics can help restore microbial biodiversity and recover lost metabolic pathways. The goal of these interventions is to restore the functionality of the immune system in sea turtles undergoing rehabilitation at specialized centers. The gut microbiome plays a crucial role in sea turtle health, sparking discussions and investigations that can potentially lead to promising treatments for these animals.

Dietary Supplementation of Compound Probiotics Improves Intestinal Health by Modulated Microbiota and Its SCFA Products as Alternatives to In-Feed Antibiotics

Enterococcus faecium, Bifidobacterium, and Pediococcus acidilactici, as intestinal probiotics, have been proved to play a positive role in treating intestinal diseases, promoting growth and immune regulation in poultry. The aim of this study was to evaluate the effect of compound probiotics on growth performance, digestive enzyme activity, intestinal microbiome characteristics, as well as intestinal morphology in broiler chickens. Treatment diets with chlortetracycline and compound probiotics were used for two groups of sixty broilers each throughout the feeding process. Another group was fed the basal diet. The BW (2589.41 ± 13.10 g vs 2422.50 ± 19.08 g) and ADG (60.57 ± 0.31 g vs 56.60 ± 0.45 g) of the compound probiotics added feed treatment group were significantly increased, and the FCR was significantly decreased (P < 0.05). The supplementation of a compound probiotics enhanced the abundance of beneficial bacteria such as Lactobacillus, Faecalibacterium, and norank_f_norank_o_Clostridia_vadinBB60_group (P < 0.05), and modulated the cecal microbiota structure, thereby promoting the production of short-chain fatty acids (SCFAs) and elevating their levels (P < 0.05), particularly propionic and butyric acids. Furthermore, the administration of the compound probiotics supplements significantly enhanced the villi height, V/C ratio, and reduced the crypt depth (P < 0.05). In addition, the activity of digestive enzymes in the duodenum and jejunum was elevated (P < 0.05). Collectively, the selected compound probiotics supplemented in this experiment have demonstrated efficacy, warranting further application in practical production settings as a viable alternative to antibiotics, thereby facilitating efficient production and promoting gastrointestinal health.

Exploring the role and mechanism of potential probiotics in mitigating the shrimp pathogens

Shrimp aquaculture has rapidly developed into a significant industry worldwide, providing not only financial gain and high-quality food but also tens of thousands of trained and competent workers. Frequent diseases are now regarded as a significant risk factor for shrimp aquaculture, as they have the potential to significantly reduce shrimp production and result in economic losses. Over the years various traditional methods including the use of antibiotics have been followed to control diseases yet unsuccessful. Probiotic is considered potential supplements for shrimps during farming, they may also act beneficially as disease control and increased production. Probiotics are described as a live microbial supplement that benefits the host by modifying the microbial population associated with the host and its ambient. The present state of research about probiotics demonstrates notable impacts on the immune defences of the host's gastrointestinal system, which play a crucial role in safeguarding against diseases and managing inflammation inside the digestive tract. In the past ten years, many studies on probiotics have been published. However, there is a lack of information about the processes by which probiotics exert their effects in aquaculture systems, with only limited elucidations being offered. This study explores the variety of procedures behind the positive effects of probiotics in shrimp culture. These mechanisms include the augmentation of the immune system, control of growth, antagonistic action against pathogens, competitive exclusion, and modification of the gut microbiota. Mechanisms involved in the probiotic mode of action are mostly interlinked. This provides a greater understanding of the importance of probiotics in shrimp culture as an environmentally friendly practice.

A native strain of Bacillus subtilis increases lipid accumulation and modulates expression of genes related to digestion and amino acid metabolism in Litopenaeus vannamei

In the field of shrimp aquaculture, the utilization of probiotics represents a promising avenue, due to the well-documented benefits conferred by these microorganisms. In the current study, a Bacillus subtilis strain, referred to as strain E, was isolated from the gastrointestinal tract of the shrimp Litopenaeus vannamei and subsequently identified via molecular methods and phylogeny. The probiotic potential of strain E was characterized, and its application as a feed shrimp additive was evaluated in a 45-day experiment. Several parameters were assessed, including zootechnical performance, muscle tissue proximate composition, hepatopancreas lipid concentration, and the expression of genes associated with digestion, amino acid metabolism, and antioxidant defense mechanisms in various shrimp tissues. Although no significant impact on zootechnical performance was observed, supplementation with strain E led to an increase in lipid concentration within both muscle and hepatopancreas tissues. Furthermore, a marked decrease in the expression of genes linked to digestion and amino acid metabolism was noted. These findings suggest that the addition of the B. subtilis strain E to shrimp feed may enhance nutrient absorption and modulate the expression of genes related to digestion and amino acid metabolism.

Acetolactate Decarboxylase as an Important Regulator of Intracellular Acidification, Morphological Features, and Antagonism Properties in the Probiotic Lactobacillus reuteri

SCORE

This study identifies the coding gene (aldB) of acetolactate decarboxylase (ALDC) as an important regulatory gene of the intracellular pH in Lactobacillus reuteri (L. reuteri), uncovering the important role of ALDC in regulating intracellular pH, morphological features, and antagonism properties in the probiotic organism L. reuteri.

METHODS AND RESULTS

The aldB mutant (ΔaldB) of L. reuteri is established using the homologous recombination method. Compare to the wild-type (WT) strain, the ΔaldB strain shows a smaller body size, grows more slowly, and contains more acid in the cell cytoplasm. The survival rate of the ΔaldB strain is much lower in low pH and simulated gastric fluid (SGF) than that of the WT strain, but higher in simulated intestinal fluid (SIF). The antagonism test demonstrates the ΔaldB strain can inhibit Listeria monocytogenes (L. monocytogenes) and Salmonella more effectively than the WT strain. Additionally, there is a dramatic decrease in the adhesion rate of Salmonella to Caco-2 and HT-29 cells in the presence of the ΔaldB strain compared to the WT strain. Simultaneously analyze, the auto-aggregation, co-aggregation, cell surface hydrophobicity (CSH), hemolytic, temperature, NaCl, oxidative stress, and antibiotic susceptibility of the ΔaldB strain are consistent with the features of probiotics.

CONCLUSION

This study highlights that the aldB gene plays a significant role in the growth and antibacterial properties of L. reuteri.

Postbiotic as Novel Alternative Agent or Adjuvant for the Common Antibiotic Utilized in the Food Industry

BACKGROUND

Antibiotic resistance is a serious public health problem as it causes previously manageable diseases to become deadly infections that can cause serious disability or even death. Scientists are creating novel approaches and procedures that are essential for the treatment of infections and limiting the improper use of antibiotics in an effort to counter this rising risk.

OBJECTIVES

With a focus on the numerous postbiotic metabolites formed from the beneficial gut microorganisms, their potential antimicrobial actions, and recent associated advancements in the food and medical areas, this review presents an overview of the emerging ways to prevent antibiotic resistance.

RESULTS

Presently, scientific literature confirms that plant-derived antimicrobials, RNA therapy, fecal microbiota transplantation, vaccines, nanoantibiotics, haemofiltration, predatory bacteria, immunotherapeutics, quorum-sensing inhibitors, phage therapies, and probiotics can be considered natural and efficient antibiotic alternative candidates. The investigations on appropriate probiotic strains have led to the characterization of specific metabolic byproducts of probiotics named postbiotics. Based on preclinical and clinical studies, postbiotics with their unique characteristics in terms of clinical (safe origin, without the potential spread of antibiotic resistance genes, unique and multiple antimicrobial action mechanisms), technological (stability and feasibility of largescale production), and economic (low production costs) aspects can be used as a novel alternative agent or adjuvant for the common antibiotics utilized in the production of animal-based foods.

CONCLUSION

Postbiotic constituents may be a new approach for utilization in the pharmaceutical and food sectors for developing therapeutic treatments. Further metabolomics investigations are required to describe novel postbiotics and clinical trials are also required to define the sufficient dose and optimum administration frequency of postbiotics.

Probiotic-Fermented Distillers Grain Alters the Rumen Microbiome, Metabolome, and Enzyme Activity, Enhancing the Immune Status of Finishing Cattle

A total of 30 Simmental crossbred cattle (6.50 months old, 265.0 ± 22.48 kg) were randomly divided into three groups, with 10 heads per group, and fed for 45 days. The diet treatments consisted of the Control group without PFDG supplementation, the PFDG-15% group with 15% PFDG substituting for 15% concentrate, and PFDG-30% group with 30% PFDG substituting for 30% concentrate. The results showed that compared with the Control group, the average daily gain (ADG) of the cattle in the PFDG-30% group decreased significantly (0.890 vs. 0.768 kg/d, p = 0.005). The serum malondialdehyde content of cattle in the PFDG-15% and PFDG-30% groups decreased significantly (p = 0.047) compared to that of the Control group. However, the serum superoxide dismutase activity of cattle in the PFDG-30% group was significantly higher than that of the Control group (p = 0.047). Meanwhile, both the PFDG-15% and PFDG-30% groups (1758.47 vs. 2061.30 μg/mL) showed higher serum levels of immunoglobulin G, while the interleukin-10 concentration was lower in the PFDG-30% group (p = 0.027). In addition, the PFDG-15% and PFDG-30% groups shifted the rumen microbiota by improving the abundances of F082 (related to propionic acid production) and fiber-degrading bacteria (Lachnospiraceae_UGG-009 and Prevotellaceae_UCG-001) and reducing the abundance of the disease-associated bacteria Selenomonas. A Kyoto encyclopedia of genes and genomes (KEGG) analysis illustrated that three key metabolic pathways, including phenylalanine metabolism, pyrimidine metabolism, and tryptophan metabolism, were enriched in the PFDG-15% group, but eight key metabolic pathways, including arachidonic acid metabolism, were enriched in the PFDG-30% group. Importantly, both the PFDG-15% and PFDG-30% groups increased (p < 0.01) the activities of cellulase, lipase, and protease in the rumen. Finally, the different bacterial abundance in the rumen was associated with changes in the ADG, serum antioxidant capacity, immune status, rumen enzyme activity, and metabolites. These results suggest that PFDG alters rumen microbiome abundance, metabolome, and enzyme activity for enhancing serum antioxidant capacity and the immune status, but when the supplemental level reaches 30%, it has a negative effect on ADG and the anti-inflammatory factors in finishing cattle.

Functionality of probiotics on the resistance capacity of shrimp against white spot syndrome virus (WSSV)

Shrimp aquaculture is currently regarded as a significant commercial and food production sector due to its growing importance as a source of human-consumable protein, As shrimp farming has become more intensive, disease outbreaks have become more common, necessitating the overuse of antimicrobial drugs, which has had a number of unintended consequences. The white spot syndrome virus (WSSV) is now recognized as one of the world's most pervasive and potentially fatal diseases affecting shrimp. However, there is currently no cure to prevent the disease's uncontrolled incidence and spread. Probiotics are currently favoured over these antimicrobial substances because of their ability to stimulate disease resilience in shrimp farms by strengthening the immune systems naturally. Probiotics for bacterial infections such as vibriosis are well documented, whereas research is still required to identify the legitimate strains for viral diseases. The utilization of these probiotics as a therapy for and preventative measure against WSSV in shrimp farming is a cutting-edge method that has proven to be effective. Some probiotic strains, such as Bacillus spp, Lactobacillus, and Pediococcus pentosaceus, have been displayed to enhance the innate immunity of shrimp against WSSV, reduce viral load, increase digestibility and growth, and support the gut microbiome of the host in multiple investigations. The present review explores recent developments regarding the function of probiotics in shrimp, with a focus on their anti-WSSV activity.

Effect of Clostridium butyricum on intestinal microbiota and resistance to Vibrio alginolyticus of Penaeus vannamei

In order to evaluate the effect of Clostridium butyricum (C. butyricum) feeding on intestinal microorganisms and protection against infection by Vibrio alginolyticus (V. alginolyticus) in Penaeus vannamei (P. vannamei). We set up two groups, CG30 (fed normal feed) and CB30 (fed feed supplemented with C. butyricum), for the 30d C. butyricum feeding test, and four groups, CG (CG30 group injected with PBS), CB (CB30 group injected with PBS), VACG (CG30 group injected with V. alginolyticus), and VACB (CB30 group injected with V. alginolyticus), for the 24h infection test. The protective effect of C. butyricum against acute V. alginolyticus infection in P. vannamei was explained in terms of survival, histopathology, changes in enzyme activity, transcriptome analysis, and immune-related genes. We found that feeding C. butyricum significantly altered intestinal microbial populations' abundance and significantly reduced Vibrio spp. In the V. alginolyticus stress test, C. butyricum improved the survival rate and alleviated pathological changes in hepatopancreatic tissues, alleviated the reduction of superoxide dismutase (SOD) and phenoloxidase (PO) activity caused by infection, and increased the lysozyme content in P. vannamei. VACB group compared with the VACG group, 1730 up-regulated differentially expressed genes (DEGs) and 2029 down-regulated DEGs were screened. Quantitative real-time PCR (qRT-PCR) showed that dietary supplementation with C. butyricum suppressed the upregulation of alkaline phosphatase (AKP) transcription factors and the downregulation of prophenoloxidase (proPO), alpha-2-macroglobulin (A2M), and anti-lipopolysaccharide factor (ALF) induced by V. alginolyticus infection. In conclusion, feed supplementation with C. butyricum changed P. vannamei's population ratio of intestinal microorganisms. Moreover, C. butyricum has the potential to act as an inhibitor of V. alginolyticus infection and enhance the resistance of P. vannamei to V. alginolyticus infection.

Screening of host gut-derived probiotics and effects of feeding probiotics on growth, immunity, and antioxidant enzyme activity of hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂)

In recent years, the widespread use of antibiotics in intensive grouper mariculture has resulted in the ineffectiveness of antibiotic treatment, leading to an increasing incidence of diseases caused by bacteria, viruses, and parasites, causing serious economic losses. Hence, it is crucial to develop alternative strategies to antibiotics for healthy and sustainable development of the mariculture industry. Here, we aimed to screen host gut-derived probiotics and evaluate its effects on growth and immunity of grouper. In this study, 43 bacterial strains were isolated from the intestine of the hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂), and a potential probiotic strain G1-26, which can efficiently secrete amylase, protease, and lipase, was obtained using different screening mediums. Based on 16S rDNA sequencing, the potential probiotic strain G1-26 was identified as Vibrio fluvialis. The results of a biological characteristic evaluation showed that V. fluvialis G1-26 could grow at 25-45 °C, pH 5.5-7.5, salinity 10-40, and bile salt concentration 0-0.030%, and produce amylase, lipase, and protease under different culture conditions. Additionally, V. fluvialis G1-26 is sensitive to many antibiotics and does not exhibit aquatic biotoxicity. Subsequently, hybrid groupers were fed diets containing V. fluvialis G1-26 at different concentrations (0, 10⁶, 10⁸, and 10¹⁰ CFU/g) for 60 d. The results showed that V. fluvialis G1-26 at 10⁸ CFU/g did not significantly affect the growth performance of the hybrid grouper (P > 0.05). V. fluvialis G1-26 supplementation at 10⁸ and 10¹⁰ CFU/g significantly promoted the relative expression of immune-related genes in hybrid groupers (TLR3, TLR5, IL-1β, IL-8, IL-10, CTL, LysC, TNF-2, and MHC-2) and improved the activities of alkaline phosphatase, acid phosphatase, total superoxide dismutase, and total protein in the liver. In conclusion, V. fluvialis G1-26, a potential probiotic strain isolated from the intestine of the hybrid grouper, can be used as an effective immunopotentiator at an optimal dose of 10⁸ CFU/g diet. Our results provide a scientific basis for the development and utilization of probiotics in the grouper mariculture industry.

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.

Host-microbiome interaction in fish and shellfish: An overview

The importance of the gut microbiome in the management of various physiological activities including healthy growth and performance of fish and shellfish is now widely considered and being studied in detail for potential applications in aquaculture farming and the future growth of the fish industry. The gut microbiome in all animals including fish is associated with a number of beneficial functions for the host, such as stimulating optimal gastrointestinal development, producing and supplying vitamins to the host, and improving the host's nutrient uptake by providing additional enzymatic activities. Besides nutrient uptake, the gut microbiome is involved in strengthening the immune system and maintaining mucosal tolerance, enhancing the host's resilience against infectious diseases, and the production of anticarcinogenic and anti-inflammatory compounds. Because of its significant role, the gut microbiome is very often considered an "extra organ," as it plays a key role in intestinal development and regulation of other physiological functions. Recent studies suggest that the gut microbiome is involved in energy homeostasis by regulating feeding, digestive and metabolic processes, as well as the immune response. Consequently, deciphering gut microbiome dynamics in cultured fish and shellfish species will play an indispensable role in promoting animal health and aquaculture productivity. It is mentioned that the microbiome community available in the gut tract, particularly in the intestine acts as an innovative source of natural product discovery. The microbial communities that are associated with several marine organisms are the source of natural products with a diverse array of biological activities and as of today, more than 1000 new compounds have been reported from such microbial species. Exploration of such new ingredients from microbial species would create more opportunities for the development of the bio-pharma/aquaculture industries. Considering the important role of the microbiome in the whole life span of fish and shellfish, it is necessary to understand the interaction process between the host and microbial community. However, information pertaining to host-microbiome interaction, particularly at the cellular level, gene expression, metabolic pathways, and immunomodulation mechanisms, the available literature is scanty. It has been reported that there are three ways of interaction involving the host-microbe-environment operates to maintain homeostasis in the fish and shellfish gut i.e. host intrinsic factors, the environment that shapes the gut microbiome composition, and the core microbial community present in the gut system itself has equal influence on the host biology. In the present review, efforts have been made to collect comprehensive information on various aspects of host-microbiome interaction, particularly on the immune system and health maintenance, management of diseases, nutrient uptake, digestion and absorption, gene expression, and metabolism in fish and shellfish.

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.

Dietary supplementation of probiotics fermented Chinese herbal medicine Sanguisorba officinalis cultures enhanced immune response and disease resistance of crucian carp (Carassius auratus) against Aeromonas hydrophila

Aeromonas hydrophila, a Gram-negative bacterium, is one of the major pathogens causing bacterial sepsis in aquatic animals due to drug resistance and pathogenicity, which could cause high mortality and serious economic losses to the aquaculture. Sanguisorba officinalis (called DiYu in Chinese, DY) is well known as herbal medicine, which could inhibit the growth of pathogenic bacteria, hemostasis and regulate the immune response. Moreover, the active ingredients in DY could remarkably reduce drug resistance. In this study, we investigated the effects of probiotic fermentation cultures on A. hydrophila through in vitro and in vivo experiments. Three lactic acid bacteria, including Lactobacillus rhamnosus (LGG), Lactobacillus casei (LC) and Lactobacillus plantarum (LP), were selected to ferment the Chinese herbal medicine DY. The assays of antagonism showed that all three fermented cultures could influence the ability of A. hydrophila growth, among which L. rhamnosus fermented DY cultures appeared to be the strongest inhibitory effect. In addition, the biofilm determination revealed that L. rhamnosus fermented DY cultures could significantly inhibit the biofilm formation of A. hydrophila compared to the other groups. Furthermore, protease, lecithinase and urease activities were found in the three fermentation cultures. Three probiotics fermented DY cultures were orally administration with crucian carp to evaluate the growth performance, immunological parameters and pathogen resistance. The results showed that the three fermentation cultures could promote the growth performance of crucian carp, and the immunoglobulins, antioxidant-related enzymes and immune-related genes were significantly enhanced. Besides, the results showed that crucian carp received L. rhamnosus (60.87%), L. casei (56.09%) and L. plantarum (41.46%) fermented DY cultures had higher survival rates compared with the control group after infection with A. hydrophila. Meanwhile, the pathological tissue results revealed that the probiotic fermented cultures could largely improve the tissues damage caused by the pathogenic bacteria. In conclusion, this study proved that the fermentation cultures of three probiotics could effectively inhibit the growth of A. hydrophila, regulate the level of immune response and improve the survival rate against A. hydrophila in crucian carp. The present data suggest that probiotic fermented Sanguisorba officinalis act as a potential gut-targeted therapy regimens to protecting fish from pathogenic bacteria infection.

Effects of Dietary Pectin and Lactobacillus salivarius ATCC 11741 on Growth Performance, Immunocompetence, Gut Microbiota, Antioxidant Capacity, and Disease Resistance in Narrow-Clawed Crayfish, Postantacus leptodactylus

The present study was conducted to clarify the effects of Lactobacillus salivarius (LS) ATCC 11741 and pectin (PE) on growth performance, digestive enzymes activity, gut microbiota composition, immune parameters, antioxidant defense as well as disease resistance against Aeromonas hydrophila in narrow-clawed crayfish, Postantacus leptodactylus. During 18 weeks trial feeding, 525 narrow-clawed crayfish juvenile (8.07 ± 0.1 g) fed with seven experimental diets including control (basal diet), LS1 (1 × 10⁷ CFU/g), LS2 (1 × 109 CFU/g), PE1 (5 g/kg), PE2 (10 g/kg), LS1PE1 (1 × 10⁷ CFU/g +5 g/kg), and LS2PE2 (1 × 109 CFU/g +10 g/kg). After 18 weeks, growth parameters (final weight, weight gain, and specific growth rate) and feed conversion rate were significantly improved in all treatments (P < 0.05). Besides, diets incorporated with LS1PE1 and LS2PE2 significantly increased the activity of amylase and protease enzymes compared to LS1, LS2, and control groups (P < 0.05). Microbiological analyses revealed that the total heterotrophic bacteria count (TVC) and lactic acid bacteria (LAB) of narrow-clawed crayfish fed diets containing LS1, LS2, LS1PE1, and LS2PE2 were higher than control group. The highest total haemocyte count (THC), large-granular (LGC) and semigranular cells (SGC) count, and hyaline count (HC) was obtained in LS1PE1 (P < 0.05). Similarly, higher immunity activity (lysozyme (LYZ), phenoloxidase (PO), nitroxidesynthetase (NOs), and alkaline phosphatase (AKP)) observed in the LS1PE1 treatment compared to the control group (P < 0.05). The glutathione peroxidase (GPx) and superoxide dismutase (SOD) activity remarkably enhanced in LS1PE1 and LS2PE2, while malondialdehyde (MDA) content reduced in these two treatments. In addition, specimens belonging to LS1, LS2, PE2, LS1PE1, and LS2PE2 groups presented higher resistance against A. hydrophila compared to the control group. In conclusion, feeding narrow-clawed crayfish with synbiotic had higher efficiency on growth parameters, immunocompetence, and disease resistance compared to single consumption of prebiotics and probiotics.

Whole genome analysis of host-associated lactobacillus salivarius and the effects on hepatic antioxidant enzymes and gut microorganisms of Sinocyclocheilus grahami

As a fish unique to Yunnan Province in China, Sinocyclocheilus grahami hosts abundant potential probiotic resources in its intestinal tract. However, the genomic characteristics of the probiotic potential bacteria in its intestine and their effects on S. grahami have not yet been established. In this study, we investigated the functional genomics and host response of a strain, Lactobacillus salivarius S01, isolated from the intestine of S. grahami (bred in captivity). The results revealed that the total length of the genome was 1,737,623 bp (GC content, 33.09%), comprised of 1895 genes, including 22 rRNA operons and 78 transfer RNA genes. Three clusters of antibacterial substances related genes were identified using antiSMASH and BAGEL4 database predictions. In addition, manual examination confirmed the presence of functional genes related to stress resistance, adhesion, immunity, and other genes responsible for probiotic potential in the genome of L. salivarius S01. Subsequently, the probiotic effect of L. salivarius S01 was investigated in vivo by feeding S. grahami a diet with bacterial supplementation. The results showed that potential probiotic supplementation increased the activity of antioxidant enzymes (SOD, CAT, and POD) in the hepar and reduced oxidative damage (MDA). Furthermore, the gut microbial community and diversity of S. grahami from different treatment groups were compared using high-throughput sequencing. The diversity index of the gut microbial community in the group supplemented with potential probiotics was higher than that in the control group, indicating that supplementation with potential probiotics increased gut microbial diversity. At the phylum level, the abundance of Proteobacteria decreased with potential probiotic supplementation, while the abundance of Firmicutes, Actinobacteriota, and Bacteroidota increased. At the genus level, there was a decrease in the abundance of the pathogenic bacterium Aeromonas and an increase in the abundance of the potential probiotic bacterium Bifidobacterium. The results of this study suggest that L. salivarius S01 is a promising potential probiotic candidate that provides multiple benefits for the microbiome of S. grahami.

Role of Postbiotics in Diet-Induced Metabolic Disorders

Although the prevalence of metabolic disorders has progressively increased over the past few decades, metabolic disorders can only be effectively treated with calorie restriction and improved physical activity. Recent research has focused on altering the gut microbiome using prebiotics, probiotics, and postbiotics because various metabolic syndromes are caused by gut microbial dysbiosis. Postbiotics, substances produced or released by microorganism metabolic activities, play an important role in maintaining and restoring host health. Because postbiotics have a small amount of literature on their consumption, there is a need for more experiments on short- and long-term intake. This review discusses current postbiotic research, categories of postbiotics, positive roles in metabolic syndromes, and potential therapeutic applications. It covers postbiotic pleiotropic benefits, such as anti-obesity, anti-diabetic, and anti-hypertensive qualities, that could aid in the management of metabolic disorders. Postbiotics are promising tools for developing health benefits and therapeutic goals owing to their clinical, technical, and economic properties. Postbiotic use is attractive for altering the microbiota; however, further studies are needed to determine efficacy and safety.

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.

Evaluation of Salipiger thiooxidans and Exiguobacterium aestuarii from the Saemangeum Reservoir as Potential Probiotics for Pacific White Shrimp (Litopenaeus vannamei)

In this study, two bacterial species, Salipiger thiooxidans and Exiguobacterium aestuarii, were extracted and screened from the Saemangeum Reservoir. This study examined these species’ suitability as a probiotic by confirming the effects of S. thiooxidans and E. aestuarii added to rearing water for L. vannamei. Three experimental groups were evaluated for 6 weeks: (1) a control group reared in natural (i.e., untreated) water (CON), (2) an experimental group in which S. thiooxidans was added to natural water (SMG-A), and (3) natural water inoculated with E. aestuarii (SMG-B). The SMG-B group inoculated with E. aestuarii showed significantly higher final body weight, weight gain, specific growth rates, and feed efficiency than the control group. The SMG-B group inoculated with E. aestuarii exhibited significantly higher levels of serum lysozyme, and ACP and ALP activity than the control and SMG-A groups. The SMG-A and SMG-B groups inoculated with probiotics showed significantly lower total ammonia nitrogen and nitrite than the control group. Our findings suggest that S. thiooxidans and E. aestuarii extracted from the Saemangeum Reservoir can improve the water quality of aquaculture water, and, in particular, E. aestuarii is a potential probiotic for L. vannamei.

Turning the tide on sex and the microbiota in aquatic animals

Sex-based differences in animal microbiota are increasingly recognized as of biological importance. While most animal biomass is found in aquatic ecosystems and many water-dwelling species are of high economic and ecological value, biological sex is rarely included as an explanatory variable in studies of the aquatic animal microbiota. In this opinion piece, we argue for greater consideration of host sex in studying the microbiota of aquatic animals, emphasizing the many advancements that this information could provide in the life sciences, from the evolution of sex to aquaculture.

Dietary Probiotic Pediococcus acidilactici MA18/5M Improves the Growth, Feed Performance and Antioxidant Status of Penaeid Shrimp Litopenaeus stylirostris: A Growth-Ration-Size Approach

Simple Summary

Probiotics are increasingly documented to confer health and performance benefits across farmed animals. The study assessed the effect of dietary supplementation with the single-strain probiotic Pedicococcus acidilactici MA18/5M on the growth, nutritional indices, and metabolic status of the adult western blue shrimp, Litopenaeus stylirostris. The aim was to estimate its potential at optimizing the performance of the penaeid feed and shrimp farming industry. Supplementation with P. acidilactici MA18/5M improved the feed conversion efficiency and daily growth rate across fixed ration sizes; and decreased both the maintenance and optimal ration size for growth. This appeared linked to a better use of dietary carbohydrates as shown by a higher α-amylase activity, free-glucose and glycogen concentration in the digestive gland. Interestingly, P. acidilactici intake was also associated with a higher antioxidant status which may be linked to enhanced carbohydrates utilization. Using a fixed ration size approach under controlled laboratory conditions, the study documented a clear potential for P. acidilactici MA18/5M to enhance the growth, feed efficiency and metabolic health of adult penaeid shrimp during on-growing. These findings raise interesting prospects to optimize penaeid feed formulation and the performance of the shrimp-farming industry.

Abstract

Probiotics are increasingly documented to confer health and performance benefits across farmed animals. The aim of this study was to assess the effect of a constant daily intake of the single-strain probiotic Pedicococcus acidilactici MA18/5M (4 × 10⁸ CFU.day⁻¹.kg⁻¹ shrimp) fed over fixed, restricted ration sizes (1% to 6% biomass.day⁻¹) on the nutritional performance and metabolism of adult penaeid shrimp Litopenaeus stylirostris (initial body-weight, BWi = 10.9 ± 1.8 g). The probiotic significantly increased the relative daily growth rate (RGR) across all ration size s tested (Mean-RGR of 0.45 ± 0.08 and 0.61 ± 0.07% BWi.day⁻¹ for the control and probiotic groups, respectively) and decreased the maintenance ration (Rm) and the optimal ration (Ropt) by 18.6% and 11.3%, respectively. Accordingly, the probiotic group exhibited a significantly higher gross (K1) and net (K2) feed conversion efficiency with average improvement of 35% and 30%, respectively. Enhanced nutritional performances in shrimps that were fed the probiotic P. acidilactici was associated with, in particular, significantly higher α-amylase specific activity (+24.8 ± 5.5% across ration sizes) and a concentration of free-glucose and glycogen in the digestive gland at fixed ration sizes of 3% and below. This suggests that the probiotic effect might reside in a better use of dietary carbohydrates. Interestingly, P. acidilactici intake was also associated with a statistically enhanced total antioxidant status of the digestive gland and haemolymph (+24.4 ± 7.8% and +21.9 ± 8.5%, respectively; p < 0.05). As supported by knowledge in other species, enhanced carbohydrate utilization as a result of P. acidilactici intake may fuel the pentose-phosphate pathway, generating NADPH or directly enhancing OH-radicals scavenging by free glucose, in turn resulting in a decreased level of cellular oxidative stress. In conclusion, the growth-ration method documented a clear contribution of P. acidilactici MA18/5M on growth and feed efficiency of on-growing L. stylirostris that were fed fixed restricted rations under ideal laboratory conditions. The effect of the probiotic on α-amylase activity and carbohydrate metabolism and its link to the shrimp’s antioxidant status raises interesting prospects to optimize dietary formulations and helping to sustain the biological and economic efficiency of the penaeid shrimp-farming industry.

Probiotic Bacillus safensis NPUST1 Administration Improves Growth Performance, Gut Microbiota, and Innate Immunity against Streptococcus iniae in Nile tilapia (Oreochromis niloticus)

Probiotics are considered ecofriendly alternatives to antibiotics as immunostimulants against pathogen infections in aquaculture. In the present study, protease-, amylase-, cellulase-, and xylanase-producing Bacillus safensis NPUST1 were isolated from the gut of Nile tilapia, and the beneficial effects of B. safensis NPUST1 on growth, innate immunity, disease resistance and gut microbiota in Nile tilapia were evaluated by feeding tilapia a basal diet or basal diet containing 105 and 106-107 CFU/g for 8 weeks. The results showed that the weight gain, feed efficiency and specific growth rate were significantly increased in tilapia fed a diet containing 106 CFU/g and 107 CFU/g B. safensis NPUST1. Intestinal digestive enzymes, including protease, amylase and lipase, and hepatic mRNA expression of glucose metabolism and growth-related genes, such as GK, G6Pase, GHR and IGF-1, were also significantly increased in the 106 CFU/g and 107 CFU/g B. safensis NPUST1 treated groups. Immune parameters such as phagocytic activity, respiratory burst and superoxide dismutase activity in head kidney leukocytes, serum lysozyme, and the mRNA expression of IL-1β, IL-8, TNF-α and lysozyme genes were significantly induced in the head kidney and spleen of 106 CFU/g and 107 CFU/g B. safensis NPUST1 treated fish. The cumulative survival rate was significantly increased in fish fed a diet containing 106 CFU/g and 107 CFU/g B. safensis NPUST1 after challenge with Streptococcus iniae. Dietary supplementation with B. safensis NPUST1 improves the gut microbiota of Nile tilapia, which increases the abundance of potential probiotics and reduces the abundance of pathogenic pathogens. The present study is the first to report the use of B. safensis as a potential probiotic in aquaculture, and a diet containing 106 CFU/g B. safensis NPUST1 is adequate for providing beneficial effects on growth performance and health status in tilapia.

A new insight to characterize immunomodulation based on hepatopancreatic transcriptome and humoral immune factor analysis of the Cherax quadricarinatus infected with Aeromonas veronii

Cherax quadricarinatus is a type of large freshwater crayfish that is characterized by rapid growth and formidable adaptability. It has also been widely cultured and studied as a model organism. Aeromonas veronii is the dominant pathogen in aquatic environments and the primary threat to aquaculture's economic stability. To better understand the interactions between C. quadricarinatus and A. veronii, high-throughput RNA sequencing of the C. quadricarinatus hepatopancreas was carried out on a control group, susceptible group (6 h after infection), and resistant group (48 h after infection). A total of 65,850,929 genes were obtained. Compared with the control group, 2616 genes were up-regulated and 1551 genes were down-regulated in the susceptible group; while 1488 genes were up-regulated and 1712 genes were down-regulated in the resistant group. GO and KEGG analysis showed that these differentially expressed genes (DEGs) were associated with multiple immune pathways, including Toll-like receptors (TLRs), antigen processing and presentation, NOD-like receptor signaling pathway, phagosome, lysosome, JAK-STAT signaling pathway. qRT-PCR showed that infection by A. veronii changed the expression pattern of the serine proteinase inhibitor (SPI), crustacean hyperglycemic hormone (CHH), anti-lipopolysaccharide factor (ALF), and extracellular copper/zinc superoxide dismutase (SOD1), all of which were significantly higher than in the control group up to 48 h after infection. In addition, detection of superoxide dismutase (SOD), catalase (CAT), lysozyme (LZM), and phenoloxidase (PO) activity, as well as ceruloplasmin (CP) concentration at different times after infection showed diverse trends. Furthermore, pathological sections obtained 24 h after infection show lesions on the hepatopancreas and intestinal tissues caused by A. veronii. The results of this study provide a foundation for analyzing the immune mechanism of C. quadricarinatus infected with A. veronii at the transcriptional level and a theoretical basis for screening disease-resistant individuals to ensure healthy economic development of the aquatic industry.

Probiotic Properties of New Lactobacillus Strains Intended to Be Used as Feed Additives for Monogastric Animals

The study aimed to evaluate the safety and probiotic properties of selected Lactobacillus strains, which are intended to be fed to monogastric animals. The Lactobacillus spp. appeared to be safe since they did not degrade mucus and did not exhibit β-haemolysis. Moreover, the survival of Caco-2 cells in the presence of metabolites of the selected strains was high, which also indicated their safety. The analysed strains showed moderate or strong antagonistic activity against Salmonella spp., Listeria monocytogenes, Campylobacter jejuni and Campylobacter coli, which was tested with the usage of the agar slab method. Furthermore, the strains showed high survivability in an acidic environment and the presence of bile salts (~90%). High resistivity or moderate susceptibility to antibiotics was also observed, as a result of the disc diffusion method. The strains were mostly moderately hydrophilic (hydrophobicity: 10.43–41.14%); nevertheless, their auto-aggregation capability exceeded 50% and their co-aggregation with pathogens varied between 12.12 and 85.45%. The ability of the selected strains to adhere to Caco-2 cells was also analysed; they were found to be moderately adhesive (85.09–95.05%) and able to hinder pathogens attaching to the cells (up to 62.58%). The analysed strains exhibit probiotic properties, such as high survivability and adherence to epithelial cells; therefore, they are suitable for administration to monogastric animals. Since the overuse of antibiotic growth promoters in livestock leads to the spread of antibiotic-resistant pathogens and accumulation of chemotherapeutic residues in food of animal origin, it is of vital importance to introduce alternative feed additives.

Comparison of the composition and function of the gut microbiome in herdsmen from two pasture regions, Hongyuan and Xilingol

There is a close relationship between the gut microbiome and health in humans including regulation of immunity and energy metabolism. This study investigated differences in the gut microbiome of herdsmen from two regions: Hongyuan pasture in Sichuan and Xilingol pasture in Inner Mongolia. We found significant differences in the gut microbiome between the two groups. The main discriminatory species between the two groups were Bifidobacterium longum, Bifidobacterium breve, Phascolarctobacterium succinatutens, Prevotella stercorea, Prevotella copri, Eubacterium biforme, and Fusobacterium prausnitzii. The abundances of Bifidobacterium longum and Bifidobacterium breve were significantly lower in the gut microbiomes of Hongyuan herdsmen than in the gut microbiomes of Xilingol herdsmen. Functional metagenomic analysis showed that more genes were enriched in glycoside hydrolase and transposase in the gut microbiome of Hongyuan herdsmen compared with Xilingol herdsmen, suggesting a higher energy demand in the gut microbiome of Hongyuan herdsmen. Significantly more genes associated with glycolysis, starch degradation, and sucrose degradation were also found in the gut microbiome of Hong yuan herdsmen compared with Xilingol herdsmen. These results indicate that herdsmen from different pastoral regions had distinct gut microbiome composition and functions.

Intestinal response characteristic and potential microbial dysbiosis in digestive tract of Bufo gargarizans after exposure to cadmium and lead, alone or combined

The gastrointestinal tract is the largest immune organ in the body and meanwhile, accommodates a large number of microorganisms. Heavy metals could disturb the intestinal homeostasis and change the gut microbial composition. However, the information regarding the links between dysbiosis of gut microbiota and imbalance of host intestinal homeostasis induced by the mixture of heavy metals is insufficient. The present study investigates the effects of Cd/Pb, both single and combination exposure, on the growth performance, intestinal histology, digestive enzymes activity, oxidative stress and immune parameters, and intestinal microbiota in Bufo gargarizans tadpoles. Our results revealed that co-exposure of Cd-Pb induced more severe impacts not only on the host, but the intestinal microbiota. On the one hand, co-exposure of Cd-Pb significantly induced growth retardation, intestinal histological injury, decreased activities of digestive enzymes. On the other hand, Cd and Pb exposure, especially in mixed form, changed the diversity and richness, structure of microbiota. Also, the intestinal microbial composition was altered by Cd/Pb exposure (alone and combination) both at the different levels. Proteobacteria, act as front-line responder, was significantly increased in tadpoles under the exposure of metals. Finally, the functional prediction revealed that the disorders of metabolism and immune responses of intestinal microbiota was increased in tadpoles exposed to Cd/Pb (especially the mixture of Cd and Pb). Our research complements the understanding of links between changes in host fitness loss and intestinal microbiota and will add a new dimension of knowledge to the ecological risks of mixed heavy metals in amphibian.

Effects of Feed Mixed with Lactic Acid Bacteria and Carbon, Nitrogen, Phosphorus Supplied to the Water on the Growth and Survival Rate of White Leg Shrimp (Penaeus vannamei) Infected with Acute Hepatopancreatic Necrosis Disease Caused by Vibrio parahaemolyticus

Simple Summary

This study aimed to evaluate the growth, survival rate, and resistance to Acute hepatopancreatic Necrosis Disease (AHPND) of white leg shrimp (Penaeus vannamei) by using Lactobacillus plantarum, Lactobacillus fermentum, and Pediococcus pentosaceus mixed with feed, and at the same time supplying CNP in a ratio of 15:1:0.1 to the water. The result showed that shrimps were fed with feed containing lactic acid bacteria (LAB), especially L. plantarum have an effective to increased shrimp growth, stimulated non-specific immune system such as total hemocyte cells, granulocyte cells, hyaline cells, and protected shrimp to ANPND. The supply of CNP to the water have increased the intensity of V. parahaemolyticus effects on shrimp health; significantly decreased non-specific immune parameters of shrimp by 30–50%, therefore increased the AHPND infected rate and mortality of shrimp compared with without CNP group. In summary, LAB has a good effect to shrimp and the supply of CNP had significantly reduced the shrimp’s immune response and increased the susceptibility of shrimp to AHPND in both cases of use with and without LAB-containing diets.

Abstract

This study aimed to evaluate the growth, survival rate, and resistance to acute hepatopancreatic necrosis disease (AHPND) of white leg shrimp (Penaeus vannamei) by using Lactobacillus plantarum, Lactobacillus fermentum, and Pediococcus pentosaceus mixed with feed, and at the same time supplying CNP in a ratio of 15:1:0.1 to the water. As a result, the treatments that shrimp were fed with feed containing lactic acid bacteria (LAB), especially L. plantarum, have increased shrimp growth, total hemocyte cells, granulocyte cells, and hyaline cells significantly (p < 0.05) in comparison to the control group. The supply of CNP to the water has promoted the intensity of V. parahaemolyticus effects on shrimp health and significantly decreased total hemocyte cells, granulocyte cells, and hyaline cells by 30–50% in the period after three days of the challenge, except in L. plantarum treatment, which had only a 20% decrease compared to other treatments. In CNP supplying treatments, the AHPND infected rate and mortality of shrimp were higher than those in other treatments. In summary, the supply of CNP had significantly reduced the shrimp’s immune response and promoted the susceptibility of shrimp to AHPND in both cases of use with and without LAB-containing diets.

Planococcus maritimus ML1206 Isolated from Wild Oysters Enhances the Survival of Caenorhabditis elegans against Vibrio anguillarum

With the widespread occurrence of aquaculture diseases and the broad application of antibiotics, drug-resistant pathogens have increasingly affected aquatic animals’ health. Marine probiotics, which live under high pressure in a saltwater environment, show high potential as a substitute for antibiotics in the field of aquatic disease control. In this study, twenty strains of non-hemolytic bacteria were isolated from the intestine of wild oysters and perch, and a model of Caenorhabditis elegans infected by Vibrio anguillarum was established. Based on the model, ML1206, which showed a 99% similarity of 16S rRNA sequence to Planococcus maritimus, was selected as a potential marine probiotic, with strong antibacterial capabilities and great acid and bile salt tolerance, to protect Caenorhabditis elegans from being damaged by Vibrio anguillarum. Combined with plate counting and transmission electron microscopy, it was found that strain ML1206 could significantly inhibit Vibrio anguillarum colonization in the intestinal tract of Caenorhabditis elegans. Acute oral toxicity tests in mice showed that ML1206 was safe and non-toxic. The real-time qPCR results showed a higher expression level of genes related to the antibacterial peptide (ilys-3) and detoxification (ugt-22, cyp-35A3, and cyp-14A3) in the group of Caenorhabditis elegans protected by ML1206 compared to the control group. It is speculated that ML1206, as a potential probiotic, may inhibit the infection caused by Vibrio anguillarum through stimulating Caenorhabditis elegans to secrete antibacterial effectors and detoxification proteins. This paper provides a new direction for screening marine probiotics and an experimental basis to support the potential application of ML1206 as a marine probiotic in aquaculture.

Phenol-rich fulvic acid as a water additive enhances growth, reduces stress, and stimulates the immune system of fish in aquaculture

Aquaculture has become imperative to cover the demands for dietary animal protein. Simultaneously, it has to overcome prejudices from excessive use of antibiotics and environmental impacts. Natural supplements are traditionally applied orally. In this study, we demonstrated another pathway: the gills. Humic substances are immunostimulants and a natural part of every aquatic ecosystem, making them ideal to be used as bath stimulants. Five and 50 mg C/L of a fulvic acid-rich humic substance was added for 28 days to the water of juvenile rainbow trout (Oncorhynchus mykiss). This fulvic acid is characterized by a high content of phenolic moieties with persistent free radicals and a high electron exchange capacity. The high concentration of the fulvic acid significantly increased growth and reduced the food conversion ratio and the response to a handling-stressor. Phagocytosis and potential killing activity of head kidney leukocytes were increased, as well as the total oxyradical scavenging capacity (TOSC) and lysozyme activity in the gills. In conclusion, immunostimulation via gills is possible with our fulvic acid, and the high phenolic content improved overall health and stress resistance of fish.

Effects of single or conjoint administration of lactic acid bacteria as potential probiotics on growth, immune response and disease resistance of snakehead fish (Channa argus)

Lactic acid bacteria (LAB) has been documented to promoting growth, enhancing immunity and disease resistance. In this study, we aimed to evaluate the single or conjoint effects of Lactococcus lactis L19 (Genbank: MT102745.1) and Enterococcus faecalis W24 (Genbank: MT102746.1) isolated from the intestine of Channa argus (C. argus) on growth performance, immune response and disease resistance of C. argus. A total of 720 apparently healthy C. argus (9.50 ± 0.03 g) were randomly divided into four equal groups. Fish were fed with a basal diet (CK) supplemented with L. lactis (L19), E. faecalis (W24), and L. lactis L19 + E. faecalis W24 (L + W) at 1.0 × 10⁸ cfu/g basal diet for 56 days. After feeding, the final body weight (FBW), weight gain (WG), feed efficiency ratio (FER), specific growth rate (SGR) and protein efficiency ratio (PER) had significantly increased (p < 0.05), especially with L19. The results indicated that single or conjoint administration of LAB as potential probiotics can induce high levels of IgM, ACP, AKP, LZM, C3 and C4 activity in serum, which may effectively induce humoral immunity, and L19 induce even higher levels. Meanwhile, when compared to CK group, the results of qPCR showed that LAB administration significantly up-regulated (p < 0.05) the expression of IL-1β, IL-6, IL-10, TNF-α, IFN-γ, HSP70, HSP90, TGF-β in the spleen, head kidney, gill, liver and intestine of C. argus. After challenge with Aeromonas veronii, the survival rates in all LAB-fed groups were significantly higher (p < 0.05) than that of the CK group, and the L19 group showed the highest (63.3%) disease resistance. Our data indicated that L. lactis L19 and E. faecalis W24, as a feed additive at 1.0 × 10⁸ cfu/g feed, could promote growth performance, enhance immune response and disease resistance of C. argus, with greatest effects in fish fed L. lactis L19 for 56 days. Hence, these LAB additives could be used as promising probiotics for C. argus. L19 was more effective than W24 or the mixture of the two for promoting growth performance, enhancing immune response and disease resistance of C. argus.

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.

Supplementation of Lactobacillus plantarum or Macleaya cordata Extract Alleviates Oxidative Damage Induced by Weaning in the Lower Gut of Young Goats

Weaning usually leads to stress in livestock, which has a negative impact on their growth and development. Research on oxidative stress and inflammation induced by weaning has not been reported in goats. Here, we focused on oxidative stress profile and inflammation status of the lower gut (jejunum, ileum, and colon) of goats. First, we illustrated the status of antioxidant activity and inflammation in the intestine of young goats on pre-(2 weeks postnatal, 2 wk^pn) or post-(11 wk^pn, weaning at day 45 postnatal)-weaned period of young goats. Malondialdehyde (MDA) was higher (p < 0.0001) in jejunum and ileum of the young goats in 11 wk^pn than that in 2 wk^pn, whereas superoxide dismutase (SOD) activity was lower (p = 0.012) in the lower gut of the young goats with 11 wk^pn than that in 2 wk^pn. Furthermore, we intended to explore the protective influence of a probiotic additive (Lactobacillus plantarum (LAC) P-8, 10 g/d) and a prebiotic additive (Sangrovit^®, Macleaya cordata (MAC) extract 3.75% w/w premix, 0.3 g/d) on intestinal oxidative stress and inflammation status of early-weaned young goats (average weights of 5.63 ± 0.30 kg, weaned on d 45 postnatal). We observed that LAC reduced MDA in jejunum and ileum (p < 0.0001), increased SOD activity in ileum (p < 0.01), and increased glutathione peroxidase (GSH-Px) activity in jejunum (p < 0.05). Similarly, MAC reduced MDA contents (p < 0.0001), increased SOD activities (p < 0.01) in both of ileum and jejunum, and increased GSH-Px activity (p < 0.05) in jejunum. However, there were no differences in feed intake, average daily gain, inflammation parameters (interleukin 2 and interleukin 6), and colon oxidative stress profile (MDA, SOD, or GSH-Px) among treatments. These results provide evidence that weaning induces oxidative damage in the lower gut of young goats, and the oxidative damage in the small intestine can be reduced by adding the addition of LAC or MAC in diets depending on the region of the lower gut.

Metabolic activity of Bacillus coagulans R11 and the health benefits of and potential pathogen inhibition by this species in the intestines of laying hens under lead exposure

Probiotics are widely used in agricultural breeding for care and maintenance of animal health, especially Bacillus coagulans, a new and popular species that could replace Lactobacillus. However, lead contamination in feed might influence the beneficial function. In the present study, Bacillus coagulans R11 was used as a model bacterium to investigate the effect of lead on changes in metabolites and genes, which could influence the beneficial function on laying hen. At the laboratory scale, transcriptomics and metabolomics were used to screen the main metabolites and related genes under lead exposure. The results showed that 4-acetamidobutanoic acid, dodecanoic acid, L-3-phenyllactic acid, apigenin and daidzein, which are antioxidants and antibacterial agents, were the main metabolites, even in the 100 ppm lead exposure group (the levels of these metabolites were 1.17-, 1.10-, 4.80-, 1.43- and 1.67-fold higher in the 100 ppm group than in pure culture medium). Twenty-three genes associated with the syntheses of the above 5 main metabolites were identified. Further animal experiments showed that B. coagulans R11 feeding of laying hens under lead exposure could prevent oxidative damage by increasing T-AOC and T-SOD activity and reducing the MDA concentration in serum and reducing the abundances of potential pathogens (Escherichia coli, Pseudomonas aeruginosa and Salmonella). Further analysis also showed that the inhibition of pathogen growth was due to the regulation of gene expression, as observed by transcriptomics, and these genes were associated with the abovementioned 5 main metabolites. However, the laying rate decreased by 10.53% compared with that of the control group when the lead exposure concentration was 100 mg/kg. The present study suggested that Bacillus coagulans R11 could help prevent oxidative damage and inhibit pathogen growth in laying hens to maintain a healthy intestinal environment for daily breeding, but under high-lead conditions, Bacillus coagulans R11 feeding could decrease the laying rate.

Evaluation of Potential Probiotics Bacillus subtilis WB60, Pediococcus pentosaceus, and Lactococcus lactis on Growth Performance, Immune Response, Gut Histology and Immune-Related Genes in Whiteleg Shrimp, Litopenaeus vannamei

An eight-week feeding trial was conducted to evaluate the effects of different dietary probiotic supplements in juvenile whiteleg shrimp, Litopenaeus vannamei. A basal control diet without probiotics (CON), and five other diets by supplementing Bacillus subtilis at 10⁷ CFU/g diet (BS₇), B. subtilis (BS₈), Pediococcus pentosaceus (PP₈), and Lactococcus lactis (LL₈) at 10⁸ CFU/g diet, and oxytetracycline (OTC) at 4 g/kg diet were used. Whiteleg shrimp with initial body weights of 1.41 ± 0.05 g (mean ± SD) were fed with these diets. Growth of shrimp fed BS₈ and LL₈ diets was significantly higher than those of shrimp fed the CON diet (p < 0.05). Superoxide dismutase activity in shrimp fed PP₈ and LL₈ diets was significantly higher than that of shrimp fed the CON diet (p < 0.05). Lysozyme activity of shrimp fed probiotics and OTC diets significantly improved compared to those on the CON diet (p < 0.05). The intestinal histology showed healthier guts for shrimp fed the probiotic diets (p < 0.05). Immune-related gene expression in shrimp fed BS₈, PP₈ and LL₈ diets was recorded as significantly higher than that of shrimp fed CON and OTC diets (p < 0.05). Also, results of the challenge test for 7 days and the digestive enzyme activity of shrimp fed BS₈, PP₈, and LL₈ were significantly improved compared to those on the CON diet (p < 0.05). Therefore, these results indicated that L. lactis at 10⁸ CFU/g could be an ideal probiotic for whiteleg shrimp, and also B. subtilis WB60 and P. pentosaceus at 10⁸ CFU/g could improve the growth, immunity, histology, gene expression, digestive enzyme activity, and disease resistance, while replacing antibiotics.

Gut Microbiota Are Associated With Psychological Stress-Induced Defections in Intestinal and Blood-Brain Barriers

Altered gut microbiota has been identified during psychological stress, which causes severe health issues worldwide. The integrity of the intestinal barrier and blood-brain barrier regulates the process of bacterial translocation and can supply the nervous system with real-time information about the environment. However, the association of gut microbiota with psychological stress remains to be fully interpreted. In this study, we established a psychological stress model using an improved communication box and compared the expression of tight junction proteins in multiple regions of the intestinal (duodenum, jejunum, ileum) and blood-brain (amygdala, hippocampus) barriers between model and control rats. We also conducted fecal microbiota analysis using 16S rRNA gene sequencing. Expression levels of the stress-related indicators adrenocorticotropic hormone, NR3C1,2, and norepinephrine were increased in the model group compared to control group. Psychological stress reduced brain and intestinal levels of tight junction proteins, including claudin5, occludin, α-actin, and ZO-1. Microbiota analysis revealed elevated microbial diversity and fecal proportions of Intestinimonas, Catenisphaera, and Globicatella in the model group. Further analysis indicated a negative correlation of Allisonella and Odoribacter, as well as a positive correlation of norank_f__Peptococcaceae, Clostridium_sensu_stricto_1, and Coprococcus_2, with claudin5, occludin, α-actin, and ZO-1. Our use of a rodent model to explore the association between compromised intestinal and blood-brain barriers and altered fecal microbiota under psychological stress improves our understanding of the gut-brain axis. Here, cues converge to control basic developmental processes in the intestine and brain such as barrier function. This study provides new directions for investigating the pathogenesis of emotional disorders and the formulation of clinical treatment.

Probiotic properties and fatty acid composition of the yeast Kluyveromyces lactis M3. In vivo immunomodulatory activities in gilthead seabream (Sparus aurata)

The aim of this study was to analyze the probiotic potential, fatty acid composition and immunostimulant activities of Kluyveromyces lactis M3 isolated from a hypersaline sediment. For this purpose, K. lactis M3 resistance to different pH, salinities and bile, as well as its antioxidant capability were assayed. Furthermore, total fatty acid composition of the yeast was determined where the dominant fatty acids were palmitic, palmitoleic, oleic and linoleic acids. K. lactis M3 showed no cytotoxic effects on peripheral blood leukocytes. During an in vivo experiment in gilthead seabream (Sparus aurata), dietary K. lactis M3 supplemented at 0.55 or 1.1% of the basal diet enhanced bactericidal activity against Vibrio parahaemolyticus N16, V. harveyi Lg 16/00, and V. anguillarum CECT 43442 compared to fish fed commercial diet (control group). Finally, nitric oxide production, peroxidase activity and skin mucus lectin union levels strongly increased in fish fed K. lactis M3 with respect to the control group. The results suggested that the yeast K. lactis M3 had exhibited high antioxidant capability, and its dietary administration at 0.55 or 1% basal diet had immunostimulant activity for gilthead seabream. For all these reasons, it should be considered an appropriate probiotic candidate for the aquaculture fish industry.

Exploring the influence of the surface proteins on probiotic effects performed by Lactobacillus pentosus HC-2 using transcriptome analysis in Litopenaeus vannamei midgut

In order to understand the mediation function of surface proteins in probiotic effects executed by Lactobacillus pentosus HC-2 in midgut of Litopenaeus vannamei, the immune and digestion related enzymes and the transcriptome expression were analyzed after shrimp fed with normal HC-2 or with stripped surface proteins HC-2 by lithium chloride (LiCl) treatment. The results showed that the shrimp fed with normal HC-2 produced much higher immune and digestion related enzymes than the control group or LiCl-treated HC-2 group to defense the Vibrio parahaemolyticus E1 infection. We obtained total over 275,099 unigenes from L. vannamei midgut, 981 genes were significant differentially expressed in normal HC-2 group compared with control, 1314 genes were significant differentially expressed in LiCl-treated HC-2 group compared with control, and 1689 genes were significant differentially expressed in LiCl-treated HC-2 group compared with normal HC-2 group. The GO/KEGG enrichment analysis of the significantly different genes demonstrated that L. vannamei fed with normal HC-2 induced immune-related, signal transduction, ion homeostasis, cell-cell adhesion, response stress/stimulus, vascular endothelial growth factor and peritrophin genes up-regulation, which were important genes involved in improving the shrimp intestine immune response, nutrition and growth performance, and bacteria adhesion and colonization, but these genes were suppressed in the midgut of shrimp fed with deprived surface proteins bacteria. Taken together, these results indicated that the surface proteins were essential for HC-2 executing probiotic effects in midgut of shrimp. Our data contribute to improve the current understanding of host - Lactobacillus interaction and the probiotic mechanisms in shrimps.

Study of gastrointestinal tract viability and motility via modulation of serotonin in a zebrafish model by probiotics

Investigated gastrointestinal tract viability and effect of potential probiotics on intestinal motility and the synthesis of serotonin in a zebrafish model.