Metabolome response to temperature-induced virulence gene expression in two genotypes of pathogenic Vibrio parahaemolyticus

Functional gene transcription variation in bacterial metatranscriptomes in large freshwater Lake Ecosystems: Implications for ecosystem and human health

Little is known regarding the temporal and spatial functional variation of freshwater bacterial community (BC) under non-bloom conditions, especially in winter. To address this, we used metatranscriptomics to assess bacterial gene transcription variation among three sites across three seasons. Our metatranscriptome data for freshwater BCs at three public beaches (Ontario, Canada) sampled in the winter (no ice), summer and fall (2019) showed relatively little spatial, but a strong temporal variation. Our data showed high transcriptional activity in summer and fall but surprisingly, 89% of the KEGG pathway genes and 60% of the selected candidate genes (52 genes) associated with physiological and ecological activity were still active in freezing temperatures (winter). Our data also supported the possibility of an adaptively flexible gene expression response of the freshwater BC to low temperature conditions (winter). Only 32% of the bacterial genera detected in the samples were active, indicating that the majority of detected taxa were non-active (dormant). We also identified high seasonal variation in the abundance and activity of taxa associated with health risks (i.e., Cyanobacteria and waterborne bacterial pathogens). This study provides a baseline for further characterization of freshwater BCs, health-related microbial activity/dormancy and the main drivers of their functional variation (such as rapid human-induced environmental change and climate change).

Metabolomic analysis of serum alpha-tocopherol among men in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study

BACKGROUND/OBJECTIVES

The role of vitamin E in chronic disease risk remains incompletely understood, particularly in an un-supplemented state, and evidence is sparse regarding the biological actions and pathways involved in its influence on health outcomes. Identifying vitamin-E-associated metabolites through agnostic metabolomics analyses can contribute to elucidating the specific associations and disease etiology. This study aims to investigate the association between circulating metabolites and serum α-tocopherol concentration in an un-supplemented state.

SUBJECTS/METHODS

Metabolomic analysis of 4,294 male participants was conducted based on pre-supplementation fasting serum in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. The associations between 1,791 known metabolites measured by ultra-high-performance LC-MS/GC-MS and HPLC-determined α-tocopherol concentration were estimated using multivariable linear regression. Differences in metabolite levels per unit difference in α-tocopherol concentration were calculated as standardized β-coefficients and standard errors.

RESULTS

A total of 252 metabolites were associated with serum α-tocopherol at the Bonferroni-corrected p value (p < 2.79 × 10^-5). Most of these metabolites were of lipid and amino acid origin, with the respective subclasses of dicarboxylic fatty acids, and valine, leucine, and isoleucine metabolism, being highly represented. Among lipids, the strongest signals were observed for linoleoyl-arachidonoyl-glycerol (18:2/20:4)[2](β = 0.149; p = 8.65 × 10^-146) and sphingomyelin (D18:2/18:1) (β = 0.035; p = 1.36 × 10^-30). For amino acids, the strongest signals were aminoadipic acid (β = 0.021; p = 5.01 × 10^-13) and l-leucine (β = 0.007; p = 1.05 × 10^-12).

CONCLUSIONS

The large number of metabolites, particularly lipid and amino acid compounds associated with serum α-tocopherol provide leads regarding potential mechanisms through which vitamin E influences human health, including its role in cardiovascular disease and cancer.

Detection and correlation analysis of shellfish pathogens in Dadeng Island, Xiamen

Food poisoning is caused by pathogenic bacteria in water and aquatic products, especially bivalves (e.g., oysters, clams), which can bioaccumulate pathogenic bacteria. Polluted water and aquatic products thus pose a serious threat to human health and safety. In this study, the types of pathogenic bacteria in water samples and shellfish collected from the Dadeng offshore area in Xiamen were examined. We also analyzed the relationships between dominant pathogens and major climate and water quality parameters. Our objective was to provide reference data that may be used to help prevent bacterial infections and to improve aquatic food hygiene in Xiamen and its surrounding areas to safe levels, thus ensuring the health of Xiamen residents. We found that the main pathogenic bacteria were Vibrio and Bacillus, with the dominant pathogen being Vibrio parahaemolyticus. Physical and chemical indexes (water temperature, salinity, pH, dissolved oxygen, and turbidity) of water bodies and the 3-day accumulated rainfall were found to be important factors affecting the occurrence and abundance of V. parahaemolyticus.

The Fate of Bacteria in Human Digestive Fluids: A New Perspective Into the Pathogenesis of Vibrio parahaemolyticus

Vibrio parahaemolyticus causes the most seafood-attributed gastroenteritis outbreaks worldwide and studies on its pathogenesis during passage through the human digestive fluids are limited. An in vitro continuous model system mimicking passage through saliva, gastric and intestinal fluid was used to study the survival, morphology and virulence-related gene expression of a total of sixty pathogenic, and non-pathogenic V. parahaemolyticus strains. The changes to these three characteristics for the sixty V. parahaemolyticus strains were minimal on passage through the saliva fluid. No V. parahaemolyticus strains survived passage through gastric fluid with low pH values (2.0 and 3.0) and the cells, examined microscopically, were severely damaged. However, when the pH of gastric fluid increased to 4.0, the bacterial survival rate was 54.70 ± 1.11%, and the survival rate of pathogenic strains was higher when compared to non-pathogenic strains. Even though the bactericidal effect of intestinal fluid was lower than gastric fluid, virulence-related gene expression was enhanced in the intestinal fluid. Seafood matrices can significantly raise the pH level of gastric fluid and thus aid the survival of V. parahaemolyticus through passage from human gastric acid and progression of pathogenesis in the intestinal fluid. We confirmed these phenomena in the in vitro continuous digestion model.

Effect of quorum-quenching bacterium Bacillus sp. QSI-1 on protein profiles and extracellular enzymatic activities of Aeromonas hydrophila YJ-1

BACKGROUND

In natural environments, bacteria always live in communities with others where their physiological characteristics are influenced by each other. Bacteria can communicate with one another by using autoinducers. The current knowledge on the effect of quenching bacteria on others is limited to assess the impact of quorum-quenching bacterium Bacillus sp. QSI-1 on proteins pattern and virulence factors production of Aeromonas hydrophila YJ-1. Proteomic analysis was performed to find out protein changes and virulence factors, after 24 h co-culture.

RESULTS

Results showed that several proteins of A. hydrophila YJ-1 were altered, seventy-two differentially expressed protein spots were excised from 2-DE gels and analyzed by MALDI-TOF/TOF MS, resulting in 63 individual proteins being clearly identified from 70 spots. Among these proteins, 50 were divided into 22 classes and mapped onto 18 biological pathways. Mixed-culture growth with Bacillus sp. QSI-1 resulted in an increase of A. hydrophilia proteins involved in RNA polymerase activity, biosynthesis of secondary metabolites, flagellar assembly, and two-component systems. In contrast, mixed culture resulted in a decreased level of proteins involved in thiamine metabolism; valine, leucine and isoleucine biosynthesis; pantothenate and CoA biosynthesis. In addition, the two extracellular virulence factors, proteases and hemolysin, were significantly reduced when A. hydrophila was co-cultured with QSI-1, while only lipase activity was observed to increase.

CONCLUSIONS

The information gathered from our experiment showed that Bacillus sp. QSI-1 has a major impact on the expression of proteins, including virulence factors of A. hydrophila.

Cold Tolerance Regulated by the Pyruvate Metabolism in Vibrio parahaemolyticus

Vibrio parahaemolyticus is a common foodborne pathogen found in seafood, and represents a major threat to human health worldwide. Low-temperature storage is an important seafood processing method, but is not sufficient to completely eliminate the bacteria and avoid foodborne illness. To determine the mechanisms behind such cold tolerance, RNA-seq and iTRAQ analyses were first performed to obtain the global transcriptomic and proteomic patterns of frozen squid and clinical V. parahaemolyticus isolates under cold conditions. The integrated analysis revealed the modulation of multiple pathways such as the co-occurrence of down-regulated pyruvate metabolism and up-regulated fatty acid biosynthesis, which likely contribute to V. parahaemolyticus cold tolerance. Furthermore, we found that increasing concentrations of pyruvate can reduce the fatty acid content to influence V. parahaemolyticus growth in cold conditions. Thus, regulation of pyruvate concentration may be an effective method to control this seafood-borne pathogen.

Isolation and characterization of a virulence related Vibrio alginolyticus strain Wz11 pathogenic to cuttlefish, Sepia pharaonis

Vibrio alginolyticus is a ubiquitous marine opportunistic pathogen that can infect various hosts in marine environment. In the present study, V. alginolyticus strain Wz11 was isolated from diseased cuttlefish, Sepia pharaonis, with 20% of promoted death and high survival capacity in skin mucus and tissue liquid. Its growth, siderophore production, and expressions of haemolysin and swarming related genes were characterized under iron limited conditions. The minimal inhibitory concentration (MIC) of 2,2'-dipyridyl (DP) to V. alginolyticus strain Wz11 was 640 μM. While growth of V. alginolyticus strain Wz11 was inhibited by DP, production of iron-seizing substances, haemolytic activity and swarming motility were increased. Moreover, expressions of haemolysin related genes tlh, tdh and vah and flagellar related genes flgH, fliC, fliD and fliS were also characterized using real-time reverse transcriptase PCR. Expression of tdh was up-regulated to 7.7-fold, while expressions of tlh and vah were down-regulated to 0.016-fold and 0.03-fold, respectively. The expression of fliC, flgH, fliD and fliS was up-regulated to 4.9-, 3.8-, 8.6- and 4.5-fold, respectively. Concluded from our results suggested that V. alginolyticus strain Wz11 was considered as a potential pathogen of S. pharaonis, and iron level played an important role in the production of iron-seizing substances, and activities of haemolysin and bacterial swarming as well as their related gene expressions.

Structure, function and regulation of the thermostable direct hemolysin (TDH) in pandemic Vibrio parahaemolyticus

Vibrio parahaemolyticus is a leading cause of seafood-associated bacterial gastroenteritis. The pathogen produces the thermostable direct hemolysin (TDH), which is the sole cause of the Kanagawa phenomenon (KP), a special β-type haemolysis in the Wagatsuma agar. TDH also exerts several other biological activities, the major includes lethal toxicity, cytotoxicity, and enterotoxicity. The structure and roles of TDH and the transcriptional regulation of tdh genes, are summarized in this review, which will give a better understanding of the pathogenesis of V. parahaemolyticus.