Metagenomic and metabolomic profiling of dried shrimp (Litopenaeus vannamei) prepared by a procedure traditional to the south China coastal area.

Sun-drying is a traditional process for preparing dried shrimp in coastal area of South China, but its impacts on nutrition and the formation of flavor-contributory substances in dried shrimp remain largely unknown. This study aimed to examine the effects of the production process on the microbiota and metabolites in dried shrimp. 16S rDNA amplicon sequencing was employed to identify 170 operational taxonomic units (OTUs), with Vibrio, Photobacterium, and Shewanella emerging as the primary pathogenic bacteria in shrimp samples. Lactococcus lactis was identified as the principal potential beneficial microorganism to accrue during the dried shrimp production process and found to contribute significantly to the development of desirable shrimp flavors. LC-MS-based analyses of dried shrimp sample metabolomes revealed a notable increase in compounds associated with unsaturated fatty acid biosynthesis, arachidonic acid metabolism, amino acid biosynthesis, and flavonoid and flavanol biosynthesis throughout the drying process. Subsequent exploration of the relationship between metabolites and bacterial communities highlighted the predominant coexistence of Bifidobacterium, Clostridium, and Photobacterium contributing heterocyclic compounds and metabolites of organic acids and their derivatives. Conversely, Arthrobacter and Staphylococcus were found to inhibit each other, primarily in the presence of heterocyclic compounds. This comprehensive investigation provides valuable insights into the dynamic changes in the microbiota and metabolites of dried shrimps spanning different drying periods, which we expect to contribute to enhancing production techniques and safety measures for dried shrimp processing.

Production and Characterization of Biotinylated Anti-fenitrothion Nanobodies and Development of Sensitive Fluoroimmunoassay.

A simple and sensitive fluoroimmunoassay (FIA) based on a heavy-chain antibody (VHH) for rapid detection of fenitrothion was developed. A VHH library was constructed from an immunized alpaca, and one clone recognizing fenitrothion (namely, VHHjd8) was achieved after careful biopanning. It was biotinylated by fusing with the Avi tag and biotin ligase to obtain a fusion protein (VHHjd8-BT), showing both binding capacity to fenitrothion and the streptavidin poly-horseradish peroxidase conjugate (SA-polyHRP). Based on a competitive assay format, the absorbance spectrum of oxidized 3,3',5,5'-tetramethylbenzidine generated by SA-polyHRP overlapped the emission spectrum of carbon dots, which resulted in quenching of signals due to the inner-filter effect. The developed FIA showed an IC50 value of 1.4 ng/mL and a limit of detection of 0.03 ng/mL, which exhibited 15-fold improvement compared with conventional enzyme-linked immunosorbent assay. The recovery test of FIA was validated by standard GC-MS/MS, and the results showed good consistency, indicating that the assay is an ideal tool for rapid screening of fenitrothion in bulk food samples.

Comparative transcriptomic analysis of surf clams (Paphia undulate) infected with two strains of Vibrio spp. reveals the identity of key immune genes involved in host defense.

BACKGROUND: Vibrio spp. is the major infection-producing marine bacteria in commercially important bivalve Paphia undulata. The host resistance is the major determining factor for the development of pathogenesis. To explore defense mechanisms, researchers have focused primarily on the study of differential expression of individual or specific groups of host immune genes during pathogen-challenge. RESULTS: We compared the expression profile in the surf clams infected with avirulent V. alginolyticus and virulent V. parahaemolyticus to mark the possible molecular mechanisms of pathogenesis. Comparison of the differentially expressed genes between the two groups of Vibrio-infected clams revealed that the number of down-regulate genes in V. parahaemolyticus injected clams (1433) were significantly higher than the other group (169). Based on Gene Ontology classification, a large proportion of these down-regulate genes were found to be associated with cellular and molecular mechanisms for pathogen recognition, and immunity development thereby explaining the low survival rate for the V. parahaemolyticus-treated clams and suggesting a higher virulence of this bacterium towards the surf clams. Quantitative real-time PCR of 24 candidate genes related to immunity involving the JAK-STAT signaling pathway, complementary cascade, cytokine signaling pathway, oxidative stress, phagocytosis and apoptosis down regulated under V. parahaemolyticus infection, indicating compromised host defense. Furthermore, we could demonstrate a central role of JAK-STAT pathway in bacterial clearance. dsRNA mediated depletion of a clam STAT homolog gene results in dramatic increase in the infection by V. alginolyticus, a mildly pathogenic strain under control conditions. CONCLUSIONS: The difference in gene expression profiles in surf clams treated with two Vibrio species with a differential pathogenicity to P. undulate and downstream molecular analysis could enlighten on the probable molecular mechanisms of the Vibrio pathogenesis and the virulence of V. parahaemolyticus in surf clams, which also benefits to develop new strategies for disease control in surf calm aquaculture.

Ultrasensitive immunosensor for acrylamide based on chitosan/SnO2-SiC hollow sphere nanochains/gold nanomaterial as signal amplification.

An electrochemical immunosensor for ultrasensitive detection of acrylamide (AA) in water and food samples was developed. SnO2-SiC hollow sphere nanochains with high surface area and gold nanoparticles with good electroconductivity were fabricated onto the surface of a glassy carbon electrode pre-coated with chitosan. The coating antigen (AA-4-mercaptophenylacetic acid-ovalbumin conjugate, AA-4-MPA-OVA) was immobilized on the electrode. Polyclonal antibody specific for AA-4-MPA was conjugated to gold nanorod (AuNR) as primary antibody (AuNR-Ab1). Horseradish peroxidase labelled anti-rabbit antibody produced in goat was conjugated to AuNR as secondary antibody (HRP-AuNR-Ab2). For detection, the analyte (AA-4-MPA) in sample competed with coating antigen for binding with AuNR-Ab1. After washing, HRP-AuNR-Ab2 was added to capture the AuNR-Ab1, and the electrical signal was obtained by addition of hydroquinone and H2O2. After investigation of the binding ability on nanomaterials and optimization of competitive immunoassay conditions, the proposed immunosensor exhibited a sensitive response to AA with a detection limit of 45.9 ±â€¯2.7 ng kg-1, and working range of 187 ±â€¯12.3 ng kg-1 to 104 ±â€¯8.2 µg kg-1 for drinking water samples. Recoveries of AA from spiked samples were ranged from 86.0% to 115.0%. The specificity, repeatability and stability of the immunosensor were also proved to be acceptable, indicating its potential application in AA monitoring.

Development of a progesterone immunosensor based on thionine-graphene oxide composites platforms: Improvement by biotin-streptavidin-amplified system.

Progesterone (P4) is a kind of hormone that can cause neuropathic disturbances in humans when the concentration overpasses a certain degree. In this work, an electrochemical immunosensor capable of detecting P4 sensitively and selectively was developed. Thionine-graphene oxide (Thi-GO) composites with excellent biocompatibility were synthesized and coated to a clear glassy carbon electrode. P4 coating antigen (P4-OVA) was immobilized to the electrode, then sample as well as biotinylated antibody (biotin-P4 Ab) were added. The free P4 can compete with P4-OVA for binding to biotin-P4 Ab. After the further addition of streptavidin-HRP, H2O2 was introduced to develop electrical signal for quantitative determination of P4. After careful optimization of assay conditions, the proposed immunosensor showed a linear range from 0.02 to 20ngmL-1 for P4 in milk samples. The averaged recoveries from spiked samples ranged from 84.0% to 102.0%, which correlated well with standard HPLC-MS/MS. The biosensor also showed good specificity, reproducibility and stability, indicating its potential application in monitoring of P4 in a simple and low cost manner.