Myo-Inositol Restores Tilapia's Ability Against Infection by Aeromonas sobria in Higher Water Temperature

Exogenous L-Alanine promotes phagocytosis of multidrug-resistant bacterial pathogens

Multidrug-resistant bacteria present a major threat to public health that urgently requires new drugs or treatment approaches. Here, we conduct integrated proteomic and metabolomics analyses to screen for molecular candidates improving survival of mice infected with Vibrio parahaemolyticus, which indicate that L-Alanine metabolism and phagocytosis are strongly correlated with mouse survival. We also assess the role of L-Alanine in improving mouse survival by in vivo bacterial challenge experiments using various bacteria species, including V. parahaemolyticus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Functional studies demonstrate that exogenous L-Alanine promotes phagocytosis of these multidrug-resistant pathogen species. We reveal that the underlying mechanism involves two events boosted by L-Alanine: TLR4 expression and L-Alanine-enhanced TLR4 signaling via increased biosynthesis and secretion of fatty acids, including palmitate. Palmitate enhances binding of lipopolysaccharide to TLR4, thereby promoting TLR4 dimer formation and endocytosis for subsequent activation of the PI3K/Akt and NF-κB pathways and bacteria phagocytosis. Our data suggest that modulation of the metabolic environment is a plausible approach for combating multidrug-resistant bacteria infection.

Insights into the Response in Digestive Gland of Mytilus coruscus under Heat Stress Using TMT-Based Proteomics

Ocean warming can cause injury and death in mussels and is believed to be one of the main reasons for extensive die-offs of mussel populations worldwide. However, the biological processes by which mussels respond to heat stress are still unclear. In this study, we conducted an analysis of enzyme activity and TMT-labelled based proteomic in the digestive gland tissue of Mytilus coruscus after exposure to high temperatures. Our results showed that the activities of superoxide dismutase, acid phosphatase, lactate dehydrogenase, and cellular content of lysozyme were significantly changed in response to heat stress. Furthermore, many differentially expressed proteins involved in nutrient digestion and absorption, p53, MAPK, apoptosis, and energy metabolism were activated post-heat stress. These results suggest that M. coruscus can respond to heat stress through the antioxidant system, the immune system, and anaerobic respiration. Additionally, M. coruscus may use fat, leucine, and isoleucine to meet energy requirements under high temperature stress via the TCA cycle pathway. These findings provide a useful reference for further exploration of the response mechanism to heat stress in marine mollusks.

Glutamine potentiates gentamicin to kill lab-evolved gentamicin-resistant and clinically isolated multidrug-resistant Escherichia coli

INTRODUCTION

Gentamicin is a conventional antibiotic in clinic. However, with the wide use of antibiotics, gentamicin-resistant Escherichia coli (E. coli) is an ever-increasing problem that causes infection in both humans and animals. Thus, it is especially important to restore gentamicin-mediated killing efficacy.

METHOD

E. coli K12 BW25113 cells were passaged in medium with and without gentamicin and obtain gentamicin-resistant (K12-R GEN ) and control (K12-S) strains, respectively. Then, the metabonomics of the two strains were analyzed by GC-MS approach.

RESULTS

K12-R GEN metabolome was characterized as more decreased metabolites than increased metabolites. Meantime, in the most enriched metabolic pathways, almost all of the metabolites were depressed. Alanine, aspartate and glutamate metabolism and glutamine within the metabolic pathway were identified as the most key metabolic pathways and the most crucial biomarkers, respectively. Exogenous glutamine potentiated gentamicin-mediated killing efficacy in glutamine and gentamicin dose-and time-dependent manners in K12-R GEN . Further experiments showed that glutamine-enabled killing by gentamicin was effective to clinically isolated multidrug-resistant E. coli.

DISCUSSION

These results suggest that glutamine provides an ideal metabolic environment to restore gentamicin-mediated killing, which not only indicates that glutamine is a broad-spectrum antibiotic synergist, but also expands the range of metabolites that contribute to the bactericidal efficiency of aminoglycosides.

Vibrio alginolyticus Survives From Ofloxacin Stress by Metabolic Adjustment

Antibiotic-resistant Vibrio alginolyticus becomes a worldwide challenge threatening both human health and food safety. The approach in managing such infection is largely absent, despite the fact that the mechanisms of antibiotic resistance have been extensively investigated. Metabolic modulation has been documented to be a novel approach in improving antibiotic efficacy. In this study, we characterize the metabolic signature of V. alginolyticus exposed to 0.3 or 0.5 μg/ml of ofloxacin (OFX). By profiling the metabolome, we find that bacteria treated by the two different concentrations of OFX generate different metabolic signatures. While a part of these metabolites was shared by both groups, the other metabolites represent their own signatures. The pathway enrichment analysis demonstrates that the pyruvate cycle is disrupted in the bacteria treated by the 0.3 μg/ml OFX as compared to those by the 0.5 μg/ml. Importantly, the disruption of pyruvate cycle confers the capability of bacteria to survive under 0.5 μg/ml of antibiotic stress. Further analysis identifies that the fatty acid biosynthesis is elevated in bacteria treated by 0.3 μg/ml OFX, and inhibition on fatty acid completely prevents the bacteria from survival even under such dose of antibiotic stress. Our study suggests that bacteria adapt to antibiotic stress by modulating the metabolic flux for survival, which could be targeted to increase antibiotic efficacy.

A Comparative Analysis of Metabolic Profiles of Embryonic Skeletal Muscle from Lantang and Landrace Pigs

Simple Summary

The pig is one of the most important domesticated meat animals. Some studies have revealed that pigs with low meat production show more intense myogenesis at the early stage of embryonic muscle development than pigs with high meat production. Here, by gas chromatography–mass spectrometry GC–MS based metabolomics, we concluded that the nucleotide metabolism and energy metabolism of the longissimuslumborum (LL) were increased in Lantang pigs compared with Landrace pigs, indicating rapid synthesis of nucleic acids and ATP to meet the material and energy requirements of rapid cell proliferation and differentiation in Lantang pigs.

Abstract

Elucidation of the complex regulation of porcine muscle development is key to increasing pork output and improving pork quality. However, the molecular mechanisms involved in early porcine embryonic muscle development in different pig breeds remain largely unknown. Here, GC–MS based metabolomics and metabolomic profiling was used to examine the longissimus lumborum (LL) of the Lantang (LT) and the Landrace (LR) pig at embryonic day 35 (E35). Metabolites showed clear separation between LT and LR, with 40 metabolites having higher abundances in LT and 14 metabolites having lower abundances in LT compared with LR. In addition, these metabolic changes were mainly associated with nucleotide metabolism and energy metabolism, such as purine metabolism, pyrimidine metabolism, the pentose phosphate pathway, and the TCA cycle. More interestingly, the contents of DNA, RNA, and ATP per unit mass of LL tissues were higher in LT, indicating rapid synthesis of nucleic acids and ATP, to meet both the material and energy requirements of rapid cell proliferation and differentiation. Furthermore, enzyme activity associated with the TCA cycle and pentose phosphate pathway, including α-ketoglutaric dehydrogenase (KGDH), malate dehydrogenase (MDH), pyruvate dehydrogenase (PDH), succinate dehydrogenase (SDH), and glucose-6-phosphate dehydrogenase (G6PDH), were higher in LT. Based on these results, we conclude that there are significant differences in nucleotide metabolism and energy metabolism of LL between LT and LR, and we speculate that the enhanced nucleic acid metabolism and energy metabolism in LT can meet the material and energy requirements of rapid cell proliferation and differentiation, making myogenesis more intense in LT compared to LR which might be the metabolic mechanism underlying the distinct skeletal muscle development in the two breeds.

Activation of the TCA Cycle to Provide Immune Protection in Zebrafish Immunized by High Magnesium-Prepared Vibrio alginolyticus Vaccine

Vaccines are safe and efficient in controlling bacterial diseases in the aquaculture industry and are in line with green farming. The present study develops a previously unreported approach to prepare a live-attenuated V. alginolyticus vaccine by culturing bacteria in a high concentration of magnesium to attenuate bacterial virulence. Furthermore, metabolomes of zebrafish immunized with the live-attenuated vaccines were compared with those of survival and dying zebrafish infected by V. alginolyticus. The enhanced TCA cycle and increased fumarate were identified as the most key metabolic pathways and the crucial biomarker of vaccine-mediated and survival fish, respectively. Exogenous fumarate promoted expression of il1β, il8, il21, nf-κb, and lysozyme in a dose-dependent manner. Among the five innate immune genes, the elevated il1β, il8, and lysozyme are overlapped in the vaccine-immunized zebrafish and the survival from the infection. These findings highlight a way in development of vaccines and exploration of the underlying mechanisms.

Identification of Polyvalent Vaccine Candidates From Extracellular Secretory Proteins in Vibrio alginolyticus

Bacterial infections cause huge losses in aquaculture and a wide range of health issues in humans. A vaccine is the most economical, efficient, and environment-friendly agent for protecting hosts against bacterial infections. This study aimed to identify broad, cross-protective antigens from the extracellular secretory proteome of the marine bacterium Vibrio alginolyticus. Of the 69 predicted extracellular secretory proteins in its genome, 16 were randomly selected for gene cloning to construct DNA vaccines, which were used to immunize zebrafish (Danio rerio). The innate immune response genes were also investigated. Among the 16 DNA vaccines, 3 (AT730_21605, AT730_22220, and AT730_22910) were protective against V. alginolyticus infection with 47–66.7% increased survival compared to the control, while other vaccines had lower or no protective effects. Furthermore, AT730_22220, AT730_22910, and AT730_21605 also exhibited cross-immune protective effects against Pseudomonas fluorescens and/or Aeromonas hydrophila infection. Mechanisms for cross-protective ability was explored based on conserved epitopes, innate immune responses, and antibody neutralizing ability. These results indicate that AT730_21605, AT730_22220, and AT730_22910 are potential polyvalent vaccine candidates against bacterial infections. Additionally, our results suggest that the extracellular secretory proteome is an antigen pool that can be used for the identification of cross-protective immunogens.