iTRAQ-Based Proteomic Analysis of Sublethally Injured Escherichia coli O157:H7 Cells Induced by High Pressure Carbon Dioxide

Sublethally injured microorganisms in food processing and preservation: Quantification, formation, detection, resuscitation and adaption

Sublethally injured state has been recognized as a survival strategy for microorganisms suffering from stressful environments. Injured cells fail to grow on selective media but can normally grow on nonselective media. Numerous microorganism species can form sublethal injury in various food matrices during processing and preservation with different techniques. Injury rate was commonly used to evaluate sublethal injury, but mathematical models for the quantification and interpretation of sublethally injured microbial cells still require further study. Injured cells can repair themselves and regain viability on selective media under favorable conditions when stress is removed. Conventional culture methods might underestimate microbial counts or present a false negative result due to the presence of injured cells. Although the structural and functional components may be affected, the injured cells pose a great threat to food safety. This work comprehensively reviewed the quantification, formation, detection, resuscitation and adaption of sublethally injured microbial cells. Food processing techniques, microbial species, strains and food matrix all significantly affect the formation of sublethally injured cells. Culture-based methods, molecular biological methods, fluorescent staining and infrared spectroscopy have been developed to detect the injured cells. Cell membrane is often repaired first during resuscitation of injured cells, meanwhile, temperature, pH, media and additives remarkably influence the resuscitation. The adaption of injured cells negatively affects the microbial inactivation during food processing.

Proteomic analysis reveals potential factors associated with enhanced EPS production in Streptococcus thermophilus ASCC 1275

Streptococcus thermophilus ASCC 1275 has two chain length determining genes - epsC and epsD- in its eps gene cluster, and produces two times more EPS in sucrose medium than that in glucose and lactose. Hence, we investigated the influence of sugars (glucose, sucrose and lactose), at log phase (5 h) and stationary phase (10 h), on the global proteomics of S. thermophilus 1275 to understand the differentially expressed proteins (DEPs) during EPS production using isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic analysis. Among 98 DEPs in sucrose medium, most of them were mapped into EPS biosynthesis pathway and other related metabolisms. There was an upregulation of several proteins involved in sugar transport (phosphoenolpyruvate (PEP) phosphotransferase system), EPS assembly (epsG1D) and amino acid metabolism (methionine, cysteine/arginine metabolism) in sucrose medium. This study showed that increased EPS production in S. thermophilus 1275 requires a well-co-ordinated regulation of pathway involved in both EPS assembly and amino acid metabolism along with the availability of sugars. Thus, it provided valuable insights into the biosynthesis and regulation of EPS in S. thermophilus 1275, and potential gene targets for understanding high-EPS strains.

Label-Free Quantitative Proteomics Reveals the Multitargeted Antibacterial Mechanisms of Lactobionic Acid against Methicillin-Resistant Staphylococcus aureus (MRSA) using SWATH-MS Technology

The objective of the present study was to reveal the antibacterial mechanism of lactobionic acid (LBA) against methicillin-resistant Staphylococcus aureus (MRSA) using quantitative proteomics by sequential window acquisition of all theoretical mass spectra (SWATH-MS) to analyze 100 differentially expressed proteins after LBA treatment. Furthermore, multiple experiments were conducted to validate the results of the proteomic analysis including reactive oxygen species (ROS), virulence-associated gene expression, and the relative quantification of target proteins and genes by parallel reaction monitoring and quantitative real-time PCR. Combining the ultrastructure observations, proteomic analysis, and our previous research, the mode of LBA action against MRSA was speculated as cell wall damage and loss of membrane integrity; inhibition of DNA repair and protein synthesis; inhibition of virulence factors and biofilm production; induction of oxidative stress; and inhibition of metabolic pathways. These results suggest potential applications for LBA in food safety and pharmaceuticals, considering its multitarget effects against MRSA.

Physiological and proteomic response of Escherichia coli O157:H7 to a bioprotective lactic acid bacterium in a meat environment

The enterohemorrhagic Escherichia (E.) coli (EHEC) is a pathogen of great concern for public health and the meat industry all over the world. The high economic losses in meat industry and the high costs of the illness highlight the necessity of additional efforts to control this pathogen. Previous studies have demonstrated the inhibitory activity of Enterococcus mundtii CRL35 towards EHEC, showing a specific proteomic response during the co-culture. In the present work, additional studies of the EHEC-Ent. mundtii interaction were carried out: i) differential protein expression of E. coli O157:H7 NCTC12900 growing in co-culture with Ent. mundtii in a meat environment, ii) the reciprocal influence between these two microorganisms in the adhesion to extracellular matrix (ECM) proteins and iii) the possible induction of the phage W933, coding for Shiga toxin (Stx1), by Ent. mundtii CRL35. Proteomic analysis showed a significant repression of a number of E. coli NCTC12900 proteins in co-culture respect to its single culture, these mostly related to the metabolism and transport of amino acids and nucleotides. On the other hand, statistically significant overexpression of EHEC proteins involved in stress, energy production, amino acid metabolism and transcription was observed at 30 h respect to 6 h when EHEC grew in co-culture. Data are available via ProteomeXchange with identifier PXD014588. Besides, EHEC showed a decreased adhesion capacity to ECM proteins in the presence of the bioprotective strain. Finally, Ent. mundtii CRL35 did not induce the lytic cycle of W933 bacteriophage, thus indicating its potential safe use for eliminating this pathogen. Overall, this study expands the knowledge of EHEC- Ent. mundtii CRL35 interaction in a meat environment, which will certainly contribute to find out effective biological strategies to eliminate this pathogen.

The Chinese Medicinal Formulation Guzhi Zengsheng Zhitongwan Modulates Chondrocyte Structure, Dynamics, and Metabolism by Controlling Multiple Functional Proteins

Traditional Chinese medicine is one of the oldest medical systems in the world and has its unique principles and theories in the prevention and treatment of human diseases, which are achieved through the interactions of different types of materia medica in the form of Chinese medicinal formulations. GZZSZTW, a classical and effective Chinese medicinal formulation, was designed and created by professor Bailing Liu who is the only national medical master professor in the clinical research field of traditional Chinese medicine and skeletal diseases. GZZSZTW has been widely used in clinical settings for several decades for the treatment of joint diseases. However, the underlying molecular mechanisms are still largely unknown. In the present study, we performed quantitative proteomic analysis to investigate the effects of GZZSZTW on mouse primary chondrocytes using state-of-the-art iTRAQ technology. We demonstrated that the Chinese medicinal formulation GZZSZTW modulates chondrocyte structure, dynamics, and metabolism by controlling multiple functional proteins that are involved in the cellular processes of DNA replication and transcription, protein synthesis and degradation, cytoskeleton dynamics, and signal transduction. Thus, this study has expanded the current knowledge of the molecular mechanism of GZZSZTW treatment on chondrocytes. It has also shed new light on possible strategies to further prevent and treat cartilage-related diseases using traditional Chinese medicinal formulations.