Long-term effects of three compound probiotics on water quality, growth performances, microbiota distributions and resistance to Aeromonas veronii in crucian carp Carassius auratus gibelio

Integrative analysis of metagenome and metabolome provides new insights into intestinal health protection in Coilia nasus larvae via probiotic intervention

With the development of large-scale intensive feeding, growth performance and animal welfare have attracted more and more attention. Exogenous probiotics can promote the growth performance of fish through improving intestinal microbiota; however, it remains unclear whether intestinal microbiota influence physiological biomarkers. Therefore, we performed metagenomic and metabolomic analysis to investigate the effects of a 90-day Lactiplantibacillus plantarum supplementation to a basal diet (1.0 × 108 CFU/g) on the growth performance, intestinal microbiota and their metabolites, and physiological biomarkers in Coilia nasus larvae. The results showed that the probiotic supplementation could significantly increase weight and body length. Moreover, it could also enhance digestive enzymes and tight junctions, and inhibit oxidative stress and inflammation. The metagenomic analysis showed that L. plantarum supplementation could significantly decrease the relative abundance of Proteobacteria and increase the relative abundance of Firmicutes. Additionally, pathogenic bacteria (Aeromonadaceae, Aeromonas, and Enterobacterales) were inhibited and beneficial bacteria (Bacillales) were promoted. The metabolome analysis showed that acetic acid and propanoic acid were significantly elevated, and were associated with Kitasatospora, Seonamhaeicola, and Thauera. A correlation analysis demonstrated that the digestive enzymes, tight junction, oxidative stress, and inflammation effects were significantly associated with the increased acetic acid and propanoic acid levels. These results indicated that L. plantarum supplementation could improve intestinal microbial community structure and function, which could raise acetic acid and propanoic acid levels to protect intestinal health and improve growth performance in C. nasus larvae.

Multi-Omics Analysis to Understand the Effects of Dietary Proanthocyanidins on Antioxidant Capacity, Muscle Nutrients, Lipid Metabolism, and Intestinal Microbiota in Cyprinus carpio

Proanthocyanidins (Pros), a natural polyphenolic compound found in grape seed and other plants, have received significant attention as additives in animal feed. However, the specific mechanism by which Pros affect fish health remains unclear. Therefore, the aim of this study was to investigate the potential effects of dietary Pro on common carp by evaluating biochemical parameters and multi-omics analysis. The results showed that Pro supplementation improved antioxidant capacity and the contents of polyunsaturated fatty acids (n-3 and n-6) and several bioactive compounds. Transcriptomic analysis demonstrated that dietary Pro caused an upregulation of the sphingolipid catabolic process and the lysosome pathway, while simultaneously downregulating intestinal cholesterol absorption and the PPAR signaling pathway in the intestines. Compared to the normal control (NC) group, the Pro group exhibited higher diversity in intestinal microbiota and an increased relative abundance of Cetobacterium and Pirellula. Furthermore, the Pro group had a lower Firmicutes/Bacteroidetes ratio and a decreased relative abundance of potentially pathogenic bacteria. Collectively, dietary Pro improved antioxidant ability, muscle nutrients, and the diversity and composition of intestinal microbiota. The regulation of lipid metabolism and improvement in muscle nutrients were linked with changes in the intestinal microbiota.

Effects of Microorganisms on Growth Performance, Body Composition, Digestive Enzyme Activity, Intestinal Bacteria Flora and Antimicrobial Peptide (AMP) Content of Black Soldier Fly Larvae (Hermetia illucens)

Escherichia coli (EC), Staphylococcus aureus (SA), Bacillus subtilis (BS), Rhodopseudomonas palustris (RP), Saccharomyces cerevisiae (SC) and Lactobacillus plantarum (LP) were selected as feed additives for black soldier fly (Hermetia illucens) by tracking the growth performance, proximate composition, digestive ability and antibacterial peptides (AMPs) content in the first trial. Microorganism efficiency screening results showed that RP could improve growth performance, digestive ability and AMP content of H. illucens. Therefore, RP was selected to prepare the diets and was incorporated into diets for H. illucens at levels of 0 (R0), 1.22 × 106 (R1), 1.22 × 107 (R2), 1.22 × 108 (R3), 1.22 × 109 (R4) and 1.22 × 1010 (R5) CFU/g. After 5 d of feeding, larvae fed the R2-R5 diets had higher weight gain and specific growth rates. Different concentrations of RP had no significant effect on larval body composition. R4-R5 could improve the digestibility and expression of AMPs in larvae. Moreover, RP could significantly increase the abundance of Lactobacillus and Rhodopseudomonas and decrease the abundance of Proteus and Corynebacterium. Therefore, RP is superior to the other strains as a feed additive for H. illucens larvae, and we recommend the addition of 1.22 × 109-1.22 × 1010 CFU/g RP to promote the growth and AMP content of H. illucens.

Response of bacterial communities and function to dissolved organic matters in groundwater contaminated by landfill leachate

The migration and transformation of dissolved organic matter (DOM) caused by landfill leachate leakage affected the phylogenetic development of bacterial communities in groundwater around the landfill. Previous studies mainly focused on the hydrochemical properties of DOM in groundwater contaminated by landfill leachate and the relationships between groundwater quality parameters and bacterial communities. However, the changes in DOM components and bacterial communities caused by landfill leachate leakage and their correlations remained unclear. In this work, we analyzed the evolution characteristics of DOM and identified the bacterial communities and their corresponding functions in groundwater around the landfill. The results showed that DOM content in groundwater increased after the diffusion of landfill leachate to groundwater. Significant differences in characteristics between DOM components were presented at different locations in the landfill leachate plume due to the physical dilution and bacterial degradation of DOM. One of the obvious manifestations was the tendency of humic acid-like substances to accumulate at downstream points. Samples from the contaminated aquifer had higher diversity and abundance of bacterial communities than those in the uncontaminated aquifer. Anaerobic or facultative anaerobic bacteria played predominant roles in contaminated groundwater, due to the input of organic matter, nitrate, and ammonia nitrogen. Redundancy analysis indicated that the content of fulvic acid-like DOM had a conspicuous impact on the composition of bacterial communities in the polluted groundwater. Vogesella were the dominant bacteria at the genus level in groundwater around the landfill. Furthermore, Vogesella were significant for microbial utilization and played an important role in the production of fulvic acid-like DOM. These results indicated that landfill leachate pollution posed a potential threat to the structure and function of bacterial communities in groundwater, and provided a basis for exploring the interaction between DOM composition and bacterial communities in groundwater plume contaminated by landfill leachate.

Seasonal variations of microbial community structure, assembly processes, and influencing factors in karst river

The physicochemical properties and microbial communities have significant annual and seasonal changes in karst aquifers. To explore the changes of microbial community and their relationships with environmental factors, water samples were collected from a typical karst river. Microbial communities in winter (Jan-2017 and Jan-2019) were stable with high similarity in spite of the 2 years sampling interval, but the microbial communities in Aug-2017 was different from that in Aug-2018. In four sampling times, there were 275 shared genera, whose average relative abundance ranging from 89.04 to 96.27%. The winter and summer specific genera were mainly from the recharge of tributary site K6 and discharge of waste water treatment plant (K2 and K3), respectively. The deterministic processes had a more significant effect on the microbial community assembly in winter than that in summer, which was affected by environmental pressure from pollution. Furthermore, antibiotics and inorganic nitrogen pollution affected element cycles of nitrogen and sulfur indirectly through microbial ecological modules in karst river, and the denitrification and desulfurization processes were potentially inhibited. These findings contributed to understand the changes and its assembly mechanism of microbial community, as well as the feedback to environment in polluted karst river.

Effects of stocking density on the growth performance, mitophagy, endocytosis and metabolism of Cherax quadricarinatus in integrated rice-crayfish farming systems

Red claw crayfish (Cherax quadricarinatus) is an economic freshwater shrimp with great commercial potential. However, the suitable stocking density of C. quadricarinatus is still unclear in integrated rice-crayfish farming system. Thus, this study aimed to investigate the effects of stocking density on growth performance, mitophagy, endocytosis and metabolism of C. quadricarinatus. The C. quadricarinatus was reared at low density (LD, 35.73 g/m²), middle density (MD, 71.46 g/m²) and high density (HD, 107.19 g/m²) in an integrated rice-crayfish farming system. After 90 days of farming, the growth performance of C. quadricarinatus significantly decreased in the MD and HD groups relative to that in the LD group. The HD treatment caused oxidative stress and lipid peroxidation at the end of the experiment in hepatopancreas. Transcriptome analysis showed that there were 1,531 DEGs (differently expressed genes) between the LD group and HD group, including 1,028 upregulated genes and 503 downregulated genes. KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis indicated that the DEGs were significantly enriched in endocytosis and mitophagy pathways. Meanwhile, four lipid metabolism pathways, including biosynthesis of unsaturated fatty acids, fatty acid biosynthesis, glycerolipid metabolism and glycerophospholipid metabolism, exhibited an upregulated tendency in the HD group. In conclusion, our data showed that when the stocking density reached up to 207.15 g/m² in HD group, the growth performance of C. quadricarinatus was significantly inhibited in this system. Meanwhile, the data indicated that C. quadricarinatus may respond to the stressful condition via activating antioxidant defense system, endocytosis, mitophagy and metabolism-related pathways in hepatopancreas.

A mini-review on co-supplementation of probiotics and medicinal herbs: Application in aquaculture

The aquaculture industry is geared toward intensification and successfully meets half of the world's demand for fish protein. The intensive farming system exposes the animal to the risk of disease outbreaks, which has economic consequences. Antibiotics are commonly used for the health management of aquaculture species. However, this has several drawbacks, including the increase in antibiotic resistance in pathogenic bacteria and the entry of antibiotic residues into the human food chain, which is a public health and environmental concern. The potential of probiotics, prebiotics, synbiotics, and medicinal herbs as alternatives to antibiotics for the health management of aquaculture species has been investigated in numerous studies. This review discusses the potential use of combinations of probiotics and medicinal herbs as prophylactic agents in aquaculture, along with the definitions, sources, and modes of action. The positive aspects of combining probiotics and medicinal herbs on growth performance, the immune system, and disease resistance of aquaculture species are also highlighted. Overall, this review addresses the potential of combinations of probiotics and medicinal herbs as feed additives for aquaculture species and the key role of these feed additives in improving the welfare of aquaculture species.