The Adhesion and Spoilage of Shewanella putrefaciens in Tilapia

Transcriptome Analysis Reveals the Molecular Mechanism of Pseudomonas with Different Adhesion Abilities on Tilapia Decay

This study aimed to investigate the molecular mechanism of Pseudomonas with varying adhesion capabilities to Tilapia's intestinal mucus influence the spoilage potential of Tilapia. Sodium chloride(NaCl) was used as an environmental factor to regulate Pseudomonas' adhesion ability. After being exposed to 3.5% NaCl stress, the PS01 strain with low adhesion showed an enhancement in adhesion ability, while the LP-3 strain with high adhesion exhibited a decrease. Correspondingly, the expression of critical adhesion genes, such as flgC, fliC, and cheB, was found to be altered. LP-3, with high adhesion ability, was observed to promote a relative increase in Nocardioides and Cloacibacterium in fish intestines. This led to the production of more volatile compounds, including 2-octen-1-ol Z, 2,3-Octanedione, and Eicosane, thus deepening the spoilage of tilapia. LP-3, with reduced adhesion ability after NaCl regulation, showed a diminished capacity to cause fish spoilage. Transcriptomics analysis was used to examine two Pseudomonas strains that exhibited different adhesion abilities, leading to the identification of an adhesion regulatory network involving flagellar assembly regulation, bacterial chemotaxis, quorum sensing, two-component systems, biofilm formation, and bacterial secretion systems. This study identified the Pseudomonas adhesion regulatory pathway and determined 10 key adhesion-related genes.

Antimicrobial efficacy of carvacrol-loaded curdlan hydrogels for enhancing shelf-life in seafood packaging applications

As global warming and the energy crisis receive increasing attention, the development of ecofriendly functional food packaging materials has also garnered significant interest. In this study, curdlan was combined with foaming agents (Cremodan and xanthan) and a crosslinking agent (sodium trimetaphosphate) to form a porous curdlan hydrogel. The material properties of the curdlan hydrogels were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and a thermogravimetric analysis (TGA). Results showed that the 2 % curdlan hydrogel exhibited a high water content (96.2 %), and swelling (89.2 %) and reswelling abilities (89.5 %), with a distinctly porous structure and excellent thermostability. These properties make it suitable for loading carvacrol, resulting in the formation of a carvacrol/curdlan hydrogel. In the results of antimicrobial testing, the carvacrol/curdlan hydrogel showed greater antimicrobial properties against Shewanella putrefaciens (32.3 mm) and Vibrio harveyi (33.1 mm) compared to V. parahaemolyticus (24.5 mm) in inhibition zone test. Noteworthy was the certain degree of antimicrobial ability of the carvacrol/curdlan hydrogel, which continuously exhibited microbial inhibition of the total viable count (TVC) of the no-inoculated and V. parahaemolyticus-inoculated group on sea bass fillets during 6 days of storage. In addition, the carvacrol/curdlan hydrogel inhibited the S. putrefaciens-caused microbial spoilage of fish. However, the continuous antibacterial ability of carvacrol/curdlan hydrogel needs to be improved. In future work, changing the porous size of curdlan hydrogel to control the carvacrol release for elongating the durability and long-term usage will be accomplished to fit the need in functional packaging applications.

Resilient sustainable current and emerging technologies for foodborne pathogen detection

Foodborne pathogens such as Salmonella, Escherichia coli and Listeria pose significant risks to human health. The World Health Organization estimates that 2.2 million deaths per year are directly caused by foodborne and waterborne bacterial diseases worldwide. Accordingly, detecting pathogens in food is essential to ensure that our food is safe. This review explores the critical role of novel technologies in enhancing food safety practices whilst delving into adopting and integrating innovative, resilient and sustainable approaches in the food supply chain. Further, applying novel, emerging advanced analytical techniques such as Raman spectroscopy and nanotechnology based biosensors in food contamination detection is discussed. These advanced technologies show the promise of real-time monitoring, traceability, and predictive analytics to identify and mitigate potential hazards before they reach consumers. They can provide rapid and accurate results and ensure the integrity of food products. Furthermore, the herein-highlighted synergistic integration of these technologies offers a promising path toward a safer and more transparent food system, thereby addressing the challenges of today's globalised food market and laying the platform for developing multimodal technologies for affordable, sensitive and rapid pathogen detection along the different stages of the food chain, from "farm to fork".

Characterization of microbial communities in flavors and fragrances during storage

Flavors and fragrances are essential for product quality, yet they are highly susceptible to contamination due to high moisture content and rich nutrients. This study investigates microbial growth, pH changes, volatile compound dynamics, and microbial community changes during the storage of flavors and fragrances. Results indicate that total viable counts (TVC) remained stable for the first three days but increased rapidly afterward, exceeding the acceptable limit of 5 log CFU/mL by day 7. The pH levels initially rose slightly, followed by a steady decline, which indicates spoilage progression. Gas chromatography-mass spectrometry (GC-MS) analysis revealed significant degradation of key aromatic compounds, such as 5-hydroxymethylfurfural (5-HMF), vanillin, and its derivative ethyl vanillin. Whole genome shotgun (WGS) sequencing demonstrated a marked increase in microbial community richness and diversity as storage progressed, with a notable shift in composition. Early storage stages were dominated by fungal species from the Ascomycota phylum, while later stages saw a rise in spoilage-associated bacteria, particularly from the Firmicutes and Proteobacteria phyla. Throughout the storage process, Zygosaccharomyces and its dominant species, Zygosaccharomyces bailii, remained prevalent, though their average relative abundance decreased from 81.26 to 32.29%. In addition, the bacterial species Oceanobacillus sojae and Niallia nealsonii showed significant increases in relative abundance, suggesting that bacteria were one of the key contributors to the spoilage of flavors and fragrances. Functional analysis based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) database indicated a shift in metabolic pathways within the microbial community, with heightened metabolic activity correlating with spoilage. These findings provide valuable insights for improving storage methods and quality control of flavors and fragrances.

Comprehensive shotgun proteomic characterization and virulence factors of seafood spoilage bacteria

This article summarizes the characterization, by shotgun proteomics, of 11 bacterial strains identified as responsible for seafood spoilage. A total of 4455 peptide spectrum matches, corresponding to 4299 peptides and 3817 proteins were identified. Analyses of data determined the functional pathways they are involved in. The proteins identified were integrated into a protein-protein network that involves 371 nodes and 3016 edges. Those proteins are implicated in energy pathways, peptidoglycan biosynthesis, spermidine/putrescine metabolism. An additional 773 peptides were characterized as virulence factors, that participates in bacterial pathogenesis; while 14 peptides were defined as biomarkers, as they can be used to differentiate the bacterial species present. This report represents the most extensive proteomic repository available in the field of seafood spoilage bacteria; the data substantially advances the understanding of seafood decay, as well as provides fundamental bases for the recognition of the bacteria existent in seafood that cause spoilage during food processing/storage.

Coculture of Acinetobacter johnsonii and Shewanella putrefaciens Contributes to the ABC Transporter that Impacts Cold Adaption in the Aquatic Food Storage Environment

Acinetobacter johnsonii and Shewanella putrefaciens were identified as specific spoilage organisms in aquatic food. The interactions among specific spoilage organisms under cold stress have a significant impact on the assembly of microbial communities, which play crucial roles in the spoilage and cold adaptation processes. The limited understanding of A. johnsonii and S. putrefaciens interactions in the cold adaptation mechanism hinders the elucidation of their roles in protein and metabolism levels. 4D quantitative proteomic analysis showed that the coculture of A. johnsonii and S. putrefaciens responds to low temperatures through ABC transporter proteins, resulting in phospholipid transport and inner membrane components. SapA and FtsX proteins were significantly upregulated, while LolC, LolD, LolE, PotD, PotA, PotB, and PotC proteins were significantly downregulated. Metabolome assays revealed that metabolites of glutathione and spermidine/putrescin were significantly upregulated, while metabolites of arginine/lysine/ornithine were significantly downregulated and involved in the ABC transporter metabolism. The results of ultramicroscopic analyses showed that the coculture of A. johnsonii and S. putrefaciens surface combined with the presence of the leakage of intracellular contents, suggesting that the bacteria were severely damaged and wrinkled to absorb metabolic nutrients and adapt to cold temperatures.

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.