ABSTRACT
Bacterial genomes sometimes contain genes that code for homologues of global regulators, the function of which is unclear. In members of the family Enterobacteriaceae, cells express the global regulator H-NS and its paralogue StpA. In Escherichia coli, out of providing a molecular backup for H-NS, the role of StpA is poorly characterized. The enteroaggregative E. coli strain 042 carries, in addition to the hns and stpA genes, a third gene encoding an hns paralogue (hns2). We present in this paper information about its biological function. Transcriptomic analysis has shown that the H-NS2 protein targets a subset of the genes targeted by H-NS. Genes targeted by H-NS2 correspond mainly with horizontally transferred (HGT) genes and are also targeted by the Hha protein, a fine-tuner of H-NS activity. Compared with H-NS, H-NS2 expression levels are lower. In addition, H-NS2 expression exhibits specific features: it is sensitive to the growth temperature and to the nature of the culture medium. This novel H-NS paralogue is widespread within the Enterobacteriaceae. IMPORTANCE Global regulators such as H-NS play key relevant roles enabling bacterial cells to adapt to a changing environment. H-NS modulates both core and horizontally transferred (HGT) genes, but the mechanism by which H-NS can differentially regulate these genes remains to be elucidated. There are several instances of bacterial cells carrying genes that encode homologues of the global regulators. The question is what the roles of these proteins are. We noticed that the enteroaggregative E. coli strain 042 carries a new hitherto uncharacterized copy of the hns gene. We decided to investigate why this pathogenic E. coli strain requires an extra H-NS paralogue, termed H-NS2. In our work, we show that H-NS2 displays specific expression and regulatory properties. H-NS2 targets a subset of H-NS-specific genes and may help to differentially modulate core and HGT genes by the H-NS cellular pool.
ABSTRACT
RESUMEN: El objetivo del presente trabajo fue evaluar el efecto de las microemulsiones de aceite esencial de romero (AER) y árbol de té (AET) sobre el eritrocito humano y microorganismos patógenos. Para ello, se elaboraron microemulsiones de AER y AET al 8.0% (v/v), 5.0% (v/v) y 2.5% (v/v). Las microemulsiones fueron probadas sobre el eritrocito humano para determinar el porcentaje de hemólisis, el porcentaje de inhibición de hemólisis y su actividad antibacterial contra E. coli O157:H7 y S. aureus. Las microemulsiones con AER no presentaron actividad hemolítica significativa, caso contrario con las microemulsiones de AET al 8.0% (≈70%) y 5.0% (33%) que presentaron mayor actividad hemolítica. Las microemulsiones de AER protegieron significativamente al eritrocito contra la presencia de radicales libres, en comparación con aquellas de AET (p< 0.05). Además, las emulsiones de AET al 8.0% mostraron efectos antibacterianos contra E. coli O157:H7 y S. aureus mientras que AER al 8.0% solo mostraron efecto contra E. coli O157:H7. La limitante del estudio fue que no utilizamos células nucleadas para establecer si los aceites esenciales dañan el material nuclear. Sin embargo, observamos que el tipo y la cantidad de aceite utilizado pueden tener implicaciones serias sobre la membrana eritrocitaria. Se concluye que las microemulsiones de AER presentaron mejor efecto protector eritrocitario, mientras que las microemulsiones de AET presentaron mejor actividad antibacterial contra las bacterias estudiadas, pero con mayor efecto tóxico sobre el eritrocito.
ABSTRACT: The aim of the study was to evaluate the effect of microemulsions of rosemary (AER) and tea tree (AET) essential oils on human erythrocyte and pathogen bacteria. Microemulsions of each oil were prepared at 8.0% (v/v), 5.0% (v/v) and 2.5% (v/v), and they were tested on human erythrocyte to determine the hemolysis percentage, hemolysis inhibition percentage and the antibacterial capacity against E. coli O157:H7 and S. aureus. All AER microemulsions showed no significant hemolytic activity. On the contrary, AET microemulsions showed hemolytic effect but those in concentrations of 8.0% (≈70 %) and 5.0% (33%) showed the highest effect. In addition, AER microemulsions showed protective effect against free radicals in comparison with the AET microemulsions (p< 0.05). On the other hand, the AET microemulsion at 8.0% showed antibacterial effect against E. coli O157:H7 and S. aureus, and the AER at 8.0% showed antibacterial effect against E. coli O157:H7. The limitation of this study was that nucleated cells were not used to observe the damage of the essential oils on nuclear material. However, the observed damage of erythrocyte's membrane is depending on type and amount of used oil. Therefore, it can be concluded that the AER microemulsions showed better protective effect of erythrocytes, while AET microemulsions showed better antibacterial effect against the tested bacteria, although with toxic effect on the erythrocytes.
ABSTRACT
In recent years, high-energy ultrasound has been used as an alternative to improve the functional properties of various proteins, such as from milk, eggs, soy and poultry. The benefits of implementing this technology depend on the inherent characteristics of the protein source and the intensity and amplitude of the ultrasound, as well as on the pH, temperature, ionic strength, time, and all of the variables that have an effect on the physicochemical properties of proteins. Therefore, it is necessary to establish the optimal conditions for each type of food. The use of ultrasound is a promising technique in food technology with a low impact on the environment, and it has thus become known as a green technology. Therefore, this review focuses on the application of high-energy ultrasound to food; its effects on the functional properties of proteins; and how different conditions such as the frequency, time, amplitude, temperature, and protein concentration affect the functional properties.
