Antibiotic accumulation, growth performance, intestinal diversification, and function of Nile tilapia (Oreochromis niloticus) feed by diets supplemented with different doses of sulfamethoxazole.

To comprehensively investigate the effects of exposure to legal doses of sulfamethoxazole (SMZ) in Nile tilapia (Oreochromis niloticus), fishes were exposed to diets supplemented with different doses of SMZ (NS, normal feed; LS, 20 mg/kg·day; MS, 200 mg/kg·day; and HS, 1000 mg/kg·day) for 4 weeks and then fed with normal feed for 4 weeks. General SMZ accumulation, growth performance, intestinal short-chain fatty acids, intestinal flora diversity, composition, and function were systemically evaluated. Results indicated that the SMZ accumulation in O. niloticus muscles, intestinal contents, and aquaculture environment positively correlated to the exposure dose. The growth performance, measured by weight increase, was MS>LS>NS, while HS antibiotics retarded the growth. SMZ-exposed O. niloticus had an increased number of fat particles in the liver and a change in the content of intestinal SCFAs. Moreover, SMZ exposure changed the biological diversity of the intestinal flora and subsequently induced microbiota dysbiosis, primarily inhibiting the growth of Fusobacteria, especially in HS group. Overall, exposure to higher SMZ doses than the recommended ones impair general intestinal functions and provokes health risk in fish. This study highlights the importance of rational and regulated use of SMZ in aquaculture.

Transcriptome analysis of juvenile genetically improved farmed tilapia (Oreochromis niloticus) livers by dietary resveratrol supplementation.

Here we used RNA-Seq to explore the transcriptomic response and specific involvement of hepatic mRNA of juvenile Oreochromis niloticus (GIFT) as a result of dietary resveratrol supplementation (0.05 g/kg RES). More than 24,513,018 clean reads were reference genome guided assembly into 23,417 unigenes. 12,596 unigenes (29.64%) were annotated to GO database. There were 5, 179 and 1526 genes significantly differentially expressed genes at 15, 30 and 45 d respectively, and 8 KEGG pathways were enriched associated with this immune response. Hyperemia and compressed hepatic sinusoid, fibrosis of liver cell and abnormal hepatic epidermal cell revealed by H&E and SEM analysis respectively. Genes related with cytokine production (il12rb2, scfr), immune system (ig8l, hlfl, cd226, prf1l), autophagy regulation (atg4b), foxo signaling (ccnb2), steroid hormone biosynthesis (cyp3a40), fatty acid metabolism (scd1), metabolism (cacna1b) have been significantly decreased, while genes associated with such pathways above (leap-2, prdx4, mb, homer1, mif, sat1, cytbc1_8) and the pathway of protein processing in endoplasmic reticulum (cne1, tram1) have been significantly increased. These findings suggested RES activated some immune and biological process-related genes to enhance GIFT's innate immunity. It also suggested high concentration addition or long-time administration may bring negative effect in tilapia liver.

Gut microbiota analysis of juvenile genetically improved farmed tilapia (Oreochromis niloticus) by dietary supplementation of different resveratrol concentrations.

The genetically improved farmed tilapia (GIFT, Oreochromis niloticus) is cultured widely for production of freshwater fish in China, while streptococcosis, likely related to pathogenic infections, occurs frequently in juvenile, mother, and operated GIFT. The gut microbiota plays an important role in nutrient digestibility in animals, and resveratrol (RES) has been used in feed for different freshwater fish species. Therefore, understanding changes in the tilapia gut microbiota across different concentrations of dietary RES supplementation is extremely important. The gut microbiota population in tilapia at 45 d after supplementation with different concentrations (0, 0.025, 0.05, 0.1 g/kg) of dietary RES was assessed by 16S rDNA gene sequencing. A total of 5445 operational taxonomic units were identified from all samples, and 14 phyla and 81 families were identified from all fecal samples. The bacteria of the phylum Firmicutes were significantly enriched in the 0.025 g/kg RES group when compared with the controls. Proteobacteria, Firmicutes and Cyanobacteria were the most dominant three phyla in all samples. With the increasing concentrations, the proportion of beneficial microbial taxa (Acetobacteraceae and Methylobacteriaceae) increased, whereas the proportion of harmful microbial taxa decreased, eg. Streptococcaceae except for 0.1 g/kg RES groups. RES did not affect the richness and diversity in tilapia gut microbiota. These findings provide information on the diversity and differences in GIFT gut microbiota database, and may contribute to developing strategies for management of diseases and long-term sustainability of O. niloticus culture.

Hepatic transcriptome analysis of juvenile GIFT tilapia (Oreochromis niloticus), fed diets supplemented with different concentrations of resveratrol.

The GIFT (Genetically Improved Farmed Tilapia) tilapia, Oreochromis niloticus, is cultured widely for the production of freshwater fish in China. Streptococcosis, which is related to pathogenic infections, occurs frequently in juvenile and adult female GIFT individuals. Resveratrol (RES) has been used in feed to control these infections in freshwater tilapia. To address the effects of RES on tilapia, we used high-throughput RNA sequencing technology (RNA-Seq, HiSeq. 2500) to explore the global transcriptomic response and specific involvement of hepatic mRNA of juvenile O. niloticus fed with diets containing different concentrations of (0, 0.025, 0.05, and 0.1g/kg) RES. A total of > 24,513,018 clean reads were generated and then assembled into 23,244 unigenes. The unigenes were annotated by comparing them against non-redundant protein sequence (Nr), non-redundant nucleotide (Nt), Swiss-Prot, Pfam, Gene Ontology database (GO), Clusters of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, and 12,578 unigenes were annotated to the GO database. A total of 1444 (0.025g/kg RES), 1526 (0.05g/kg RES), and 3135 (0.1g/kg RES) genes were detected as significant differentially expressed genes (DEGs), when compared with the controls. A total of 6 (0.025 vs 0.05g/kg RES), 19 (0.025 vs 0.1g/kg RES), and 124 (0.05 vs 0.1g/kg RES) genes were detected as significant DEGs. Six genes, including dnah7x1, sox4, fam46a, hsp90a, ddit4, and nmrk2, were associated with an immune response. These findings provide information on the innate immunity of GIFT and might contribute to the development of strategies for the effective management of diseases and long-term sustainability of O. niloticus culture.

Effects of dietary resveratrol supplementation on hepatic and serum pro-/anti-inflammatory activity in juvenile GIFT tilapia, Oreochromis niloticus.

Dietary resveratrol (RES) supplementation may have some pharmacological effects including anti-inflammation. Previous studies have shown that Kupffer cell activation and apoptosis induction increases the transcription of pro- and anti-inflammatory cytokines. The main purpose of this study was to investigate the pro- and anti-inflammatory activities of 0.1 or 0.3 g/kg RES as a dietary supplement in juvenile freshwater tilapia (Oreochromis niloticus). The results showed that hepatic and serum immunoglobulin M (IgM) significantly decreased and increased while anti- and pro-inflammatory cytokines significantly increased and decreased, respectively, in the RES-treated groups. The expression of serum and hepatic IgM and anti-inflammatory cytokines [interleukin (IL)-10] and its inverse inhibitor interferon (IFN)-γ significantly increased while pro-inflammatory cytokine transcription significantly decreased. Hematoxylin-eosin staining and scanning electron microscopy revealed intestinal deformation, irregular goblet cells, and apoptotic cells in the 0.3 g/kg RES groups. RES (0.3 g/kg) also induced necrosis, apoptosis, reduction in Kupffer cell number, compressed sinusoids, and deformation of epidermal cells in the liver of the treated groups. In conclusion, the results of the present study show that high doses of RES were absorbed in the gut and then damaged the liver and intestinal tissue.

Dietary supplementation with rutin has pro-/anti-inflammatory effects in the liver of juvenile GIFT tilapia, Oreochromis niloticus.

Dietary supplementation with rutin may have some pharmacological qualities including anti-inflammatory effects. Kupffer cell activation resulted in increased transcription of pro- and anti-inflammatory cytokines. The main purpose of this study was to investigate the pro- and anti-inflammatory activities in juvenile freshwater tilapia, Oreochromis niloticus, in response to 0.1 or 0.3 g/kg dietary supplementation of rutin. Results showed that hepatic IgM, anti-inflammatory-cytokines, and pro-inflammatory cytokines were significantly decreased in groups treated with high doses of rutin. Hepatic IgM and anti-inflammatory cytokines (IL-10 and IFN-γ) transcripts were significantly decreased, whereas the transcripts of the pro-inflammatory cytokines, TNFα and IL-1ß were significantly decreased, whereas IL-8 was significantly increased. The number of Kupffer cells in rutin-treated groups was significantly decreased, and scanning electron micrographs showed that rutin enriched the number of gut microvilli and secretion pits. With the phenomena of cell apoptosis occurred in the rutin groups, the present study demonstrated that optimum levels of rutin may be beneficial but excessive level may cause liver impairment, which may be absorbed by the gut and then transported to the liver.

Occurrence of antibiotics and their impacts to primary productivity in fishponds around Tai Lake, China.

Antibiotics are widely used to improve the health and yields of farmed animals, including fish, but their use is accompanied by undesirable ecological effects. Relatively little is known about the water-body burden of antibiotics and their influence on primary productivity in aquaculture ecosystem. In this study, antibiotics usage within 24 fishponds, covering 4 areas, sampled 5 times, and having 5 fish species, was investigated surrounding Tai Lake in China. The study analyzed 15 antibiotics (including 5 sulfonamides, 2 quinolones, 3 ß-lactams, 3 tetracyclines, 1 amphenicol, and 1 macrolide), and all of them were detected in water samples, with a detection frequency of 2-60%. Sulfonamides were the most prevalent, and concentrations of sulfamethoxazole, sulfamonomethoxine, and florfenicol being over 2000 ng L(-1) in some samples, while the other antibiotics levels ranged from ND (no detection) to 551.18 ng L(-1). Significant differences were observed in antibiotic burden among different regions for total antibiotics, sulfonamides, quinolones, and amphenicols; among time points for quinolones, ß-lactams, and tetracyclines; and among species for quinolones and macrolides. Furthermore, basing on the risk quotient (RQ) method, the assessment revealed that florfenicol was of highest risk to algae with RQ values exceeding 0.1, while macrolide erythromycin posed the second highest risk. The partial correlation coefficient between total antibiotics and chlorophyll (a) was -0.035 that clearly indicated total antibiotics were detrimental to green algae growth, while the nutrient input and other physical - chemical factors were much more beneficial. Overall, holistic far-reaching measures of antibiotics control are recommended to preserve aquaculture ecosystem health.

Plant-plant-microbe mechanisms involved in soil-borne disease suppression on a maize and pepper intercropping system.

BACKGROUND: Intercropping systems could increase crop diversity and avoid vulnerability to biotic stresses. Most studies have shown that intercropping can provide relief to crops against wind-dispersed pathogens. However, there was limited data on how the practice of intercropping help crops against soil-borne Phytophthora disease. PRINCIPAL FINDINGS: Compared to pepper monoculture, a large scale intercropping study of maize grown between pepper rows reduced disease levels of the soil-borne pepper Phytophthora blight. These reduced disease levels of Phytophthora in the intercropping system were correlated with the ability of maize plants to form a "root wall" that restricted the movement of Phytophthora capsici across rows. Experimentally, it was found that maize roots attracted the zoospores of P. capsici and then inhibited their growth. When maize plants were grown in close proximity to each other, the roots produced and secreted larger quantities of 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) and 6-methoxy-2-benzoxazolinone (MBOA). Furthermore, MBOA, benzothiazole (BZO), and 2-(methylthio)-benzothiazole (MBZO) were identified in root exudates of maize and showed antimicrobial activity against P. capsici. CONCLUSIONS: Maize could form a "root wall" to restrict the spread of P. capsici across rows in maize and pepper intercropping systems. Antimicrobe compounds secreted by maize root were one of the factors that resulted in the inhibition of P. capsici. These results provide new insights into plant-plant-microbe mechanisms involved in intercropping systems.