Metabolic Profiling of VOCs Emitted by Bacteria Isolated from Pressure Ulcers and Treated with Different Concentrations of Bio-AgNPs

Multifaceted analysis of the effects of roasting conditions on the flavor of fragrant Camellia oleifera Abel. seed oil

Fragrant Camellia oleifera Abel. seed oil (FCSO), produced by a roasting process, is popular for its characteristic aroma. This study investigated the effects of various roasting temperatures (90℃, 120℃, 150℃, 180℃) and durations (20 min, 40 min, 60 min) on the flavor of FCSO by physicochemical properties, hazardous substances, sensory evaluation, and flavor analyses. The results showed that FCSO roasted at 120℃/20 min had a reasonable fatty acid composition with a lower acid value (0.16 mg/g), peroxide value (0.13 g/100 g), p-anisidine value (2.27), dibutyl phthalate content (0.04 mg/kg), and higher 1,1-diphenyl-2-picrylhydrazyl free radical scavenging activity (224.51 μmol TE/kg) than other samples. A multivariate analysis of FCSO flavor revealed that the 120℃/20 min group had a higher grassy flavor score (5.3 score) from nonanoic acid and a lower off-flavor score (2.2 score) from 2-methylbutyric acid. The principal component analysis showed that 120℃/20 min could guarantee the best flavor and quality of FCSO. Therefore, this information can guide the preparation of FCSO.

Volatile biomarkers of Gram-positive bacteria of clinical relevance as a tool for infection diagnosis

AIM

Volatile organic compounds (VOCs) are being studied as potential biomarkers in many infections. Therefore, this study aimed to analyze the volatile profile of three Gram-positive bacteria of clinical relevance to identify potential volatile biomarkers that allow their differentiation.

METHODS AND RESULTS

L. monocytogenes, S. aureus, and E. faecalis clinical isolates were inoculated in a thioglycollate medium until grown. Then, VOCs were extracted by solid-phase microextraction, and the data obtained were subjected to multivariate analysis. According to our results, there was a high production of aldehydes in E. faecalis. In the case of alcohols, they only increased in L. monocytogenes, while ketones were produced significantly in all three bacteria, mainly due to acetoin. Acids were produced significantly in E. faecalis and L. monocytogenes.

CONCLUSIONS

Potential biomarkers of L. monocytogenes could be 1-butanol and 2-methylbutanoic acid. In the case of E. faecalis, the VOC most related to its presence was nonanal. Lastly, potential biomarkers of S. aureus could be isoamyl butanoate and methionol, although some pyrazines have also been associated with this bacterium.

SIGNIFICANCE AND IMPACT OF THE STUDY

The identification of potential biomarkers of these clinically relevant bacteria could open the way for the diagnosis of these infections through the analysis of volatile compounds.

Metabolic profiling of bacteria with the application of polypyrrole-MOF SPME fibers and plasmonic nanostructured LDI-MS substrates

Here we present application of innovative lab-made analytical devices such as plasmonic silver nanostructured substrates and polypyrrole-MOF solid-phase microextraction fibers for metabolic profiling of bacteria. For the first time, comprehensive metabolic profiling of both volatile and non-volatile low-molecular weight compounds in eight bacterial strains was carried out with utilization of lab-made devices. Profiles of low molecular weight metabolites were analyzed for similarities and differences using principal component analysis, hierarchical cluster analysis and random forest algorithm. The results showed clear differentiation between Gram positive (G+) and Gram negative (G-) species which were identified as distinct clusters according to their volatile metabolites. In case of non-volatile metabolites, differentiation between G+ and G- species and clustering for all eight species were observed for the chloroform fraction of the Bligh & Dyer extract, while methanolic fraction failed to recover specific ions in the profile. Furthermore, the results showed correlation between volatile and non-volatile metabolites, which suggests that lab-made devices presented in the current study might be complementary and therefore, useful for species differentiation and gaining insights into bacterial metabolic pathways.

Sample Preparation in Microbial Metabolomics: Advances and Challenges

Microbial metabolomics has gained significant interest as it reflects the physiological state of microorganisms. Due to the great variability of biological organisms, in terms of physicochemical characteristics and variable range of concentration of metabolites, the choice of sample preparation methods is a crucial step in the metabolomics workflow and will reflect on the quality and reliability of the results generated. The procedures applied to the preparation of microbial samples will vary according to the type of microorganism studied, the metabolomics approach (untargeted or targeted), and the analytical platform of choice. This chapter aims to provide an overview of the sample preparation workflow for microbial metabolomics, highlighting the pre-analytical factors associated with cultivation, harvesting, metabolic quenching, and extraction. Discussions focus on obtaining intracellular and extracellular metabolites. Finally, we introduced advanced sample preparation methods based on automated systems.

Mechanisms of Metallic Nanomaterials to Induce an Antibacterial Effect

Pathogenic microorganisms, including bacteria, are becoming resistant to most existing drugs, which increases the failure of pharmacologic treatment. Therefore, new nanomaterials were studied to spearhead improvement against the same resistant pathogenic bacteria. This has increased the mortality in the world population, principally in under-developed countries. Moreover, recently there has been research to find new drug formulations to kill the most dangerous microorganisms, such as bacteria cells which should avoid the spread of disease. Therefore, lately, investigations have been focusing on nanomaterials because they can exhibit the capacity to show an antibacterial effect. These studies have been trying oriented in their ability to produce an improvement to get antibacterial damage against the same pathogenic bacteria resistance. However, there are many problems with the use of nanoparticles. One of them is understanding how they act against bacteria, "their mechanism(s) action" to induce reduction or even kill the bacterial strains. Therefore, it is essential to understand the specific mechanism(s) of each nanomaterial used to observe the interaction between bacteria cells and nanoparticles. In addition, since nanoparticles can be functionalized with different antibacterial drugs, it is necessary to consider and distinguish the antibacterial activity of the nanoparticles from the antibacterial activity of the drugs to avoid confusion about how the nanoparticles work. Knowledge of these differences can help better understand the applications of the primary nanoparticles (i.e., Ag, Au, CuO, ZnO, and TiO², among others) described in detail in this review which are toxic against various bacterial strains.

Evaluating the Antibacterial Activity and Mode of Action of Thymol-Loaded Chitosan Nanoparticles Against Plant Bacterial Pathogen Xanthomonas campestris pv. campestris

The bacterium Xanthomonas campestris pv. campestris (Xcc) causes black rot disease in cruciferous crops, resulting in severe yield loss worldwide. The excessive use of chemical pesticides in agriculture to control diseases has raised significant concern about the impact on the environment and human health. Nanoparticles have recently gained significant attention in agriculture owing to their promising application in plant disease control, increasing soil fertility and nutrient availability. In the current study, we synthesized thymol-loaded chitosan nanoparticles (TCNPs) and assessed their antibacterial activity against Xcc. The synthesis of TCNPs was confirmed by using ultraviolet–visible spectroscopy. Fourier-transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy analysis revealed the functional groups, size, and shape of TCNPs, with sizes ranging from 54 to 250 nm, respectively. The antibacterial activity of TCNPs against Xcc was investigated in vitro by liquid broth, cell viability, and live dead staining assay, and all of them demonstrated the antibacterial activity of TCNPs. Furthermore, TCNPs were found to directly inhibit the growth of Xcc by suppressing the growth of biofilm formation and the production of exopolysaccharides and xanthomonadin. The ultrastructure studies revealed membrane damage in TCNP-treated Xcc cells, causing a release of intracellular contents. Headspace/gas chromatography (GC)–mass spectrometry (MS) analysis showed changes in the volatile profile of Xcc cells treated with TCNPs. Increased amounts of carbonyl components (mainly ketones) and production of new volatile metabolites were observed in Xcc cells incubated with TCNPs. Overall, this study reveals TCNPs as a promising antibacterial candidate against Xcc.