Illuminating the landscape of host-pathogen interactions with the bacterium Listeria monocytogenes

Listeria monocytogenes has, in 25 y, become a model in infection biology. Through the analysis of both its saprophytic life and infectious process, new concepts in microbiology, cell biology, and pathogenesis have been discovered. This review will update our knowledge on this intracellular pathogen and highlight the most recent breakthroughs. Promising areas of investigation such as the increasingly recognized relevance for the infectious process, of RNA-mediated regulations in the bacterium, and the role of bacterially controlled posttranslational and epigenetic modifications in the host will also be discussed.     

From the Cover: Desorption electrospray ionization mass spectrometry reveals surface-mediated antifungal chemical defense of a tropical seaweed

Organism surfaces represent signaling sites for attraction of allies and defense against enemies. However, our understanding of these signals has been impeded by methodological limitations that have precluded direct fine-scale evaluation of compounds on native surfaces. Here, we asked whether natural products from the red macroalga Callophycus serratus act in surface-mediated defense against pathogenic microbes. Bromophycolides and callophycoic acids from algal extracts inhibited growth of Lindra thalassiae, a marine fungal pathogen, and represent the largest group of algal antifungal chemical defenses reported to date. Desorption electrospray ionization mass spectrometry (DESI-MS) imaging revealed that surface-associated bromophycolides were found exclusively in association with distinct surface patches at concentrations sufficient for fungal inhibition; DESI-MS also indicated the presence of bromophycolides within internal algal tissue. This is among the first examples of natural product imaging on biological surfaces, suggesting the importance of secondary metabolites in localized ecological interactions, and illustrating the potential of DESI-MS in understanding chemically-mediated biological processes.     

质谱分析技术在儿童代谢性肝病诊断方面的应用

质谱分析技术已被公认为代谢性疾病化学诊断的有用手段,气相色谱质谱连用法可以对130余种代谢疾病进行筛查和化学诊断,串联质谱法可对30余种脂肪酸代谢异常疾患和部分氨基酸代谢异常同时筛查,作为先天性代谢疾病的新生儿筛查手段被广泛的应用在世界各国。代谢性肝病涉及不同的代谢途径的紊乱,多种儿童代谢性肝病都有疾病的特征性代谢谱存在,因此通过质谱分析的代谢组学研究将会对这类疾病的临床诊断非常有用。     

Study of the metabolomics characteristics of patients with metabolic syndrome based on liquid chromatography quadrupole time-of-flight mass spectrometry

BackgroundMetabolic syndrome (MS) is a disease with complex pathophysiology and pathogenesis involving multiple systems of the human body. This study aimed to identify serum metabolites that are relevant to MS.Material and methodsThis study involved 40 patients with MS and 28 healthy adults, and the following data were statistically analyzed: basic clinical data, blood lipids, fasting blood glucose, blood pressure, waist circumference, and visceral fat coefficient. Serum samples from both groups were collected and analyzed by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF/MS); multivariate and univariate statistical methods were used to identify potential MS biomarkers and MS-related metabolic pathways. In addition, leucine and valine levels in serum from MS patients and normal subjects were measured using enzyme-linked immunosorbent assays (ELISAs).ResultsIn this study, 23 potential biomarkers were identified in the plasma of MS patients. These biomarkers were mainly related to metabolism; the tricarboxylic acid cycle; galactose metabolism; arachidonic acid metabolism; valine, leucine, and isoleucine degradation; and valine, leucine, and isoleucine biosynthesis. ELISAs were utilized to verify serum leucine and valine levels, and the results supported the experimental metabolomics results.ConclusionsIn total, 23 MS-related metabolites were identified in the serum; these differential metabolites were mainly associated with lipid metabolism, amino acid metabolism, glucose metabolism, purine metabolism, and other related metabolic pathways. This study shows that LC/MS-based metabolomics methods can be used to investigate the pathological changes in MS patients and identify biomarkers for the early diagnosis of MS.     

Bacterial components in the synovial tissue of patients with advanced rheumatoid arthritis or osteoarthritis: Analysis with gas chromatography‐mass spectrometry and pan‐bacterial polymerase chain reaction

Objective

To study the presence of bacterial components in the synovial tissue (ST) of patients with advanced rheumatoid arthritis (RA).

Methods

ST was collected during joint surgery from 41 RA patients. Tissue from 39 patients with osteoarthritis (OA), 4 patients with undifferentiated inflammatory arthritis (UA), and 3 cases of accidental deaths served as controls. The pan‐bacterial polymerase chain reaction (PCR) with primers for the 23S ribosomal RNA (rRNA) and 16S rRNA genes was used to detect bacterial DNA. In addition, synovial fluid (SF) samples from patients with chlamydial reactive arthritis (ReA) were also examined by the same method. The positive controls, bacterial DNA or ST spiked with different living bacteria, were analyzed alongside clinical samples. Most of the ST samples were also analyzed by gas chromatography‐mass spectrometry (GC‐MS) for determining the presence of bacteria‐derived muramic acid. Strict precautions were followed in the clinics and the laboratory to prevent contamination.

Results

In GC‐MS analysis, muramic acid was observed in the ST from 4 of 35 RA patients and from 2 of 14 OA patients, but not in ST from 2 patients with UA and 3 cadavers. Bacterial DNA was not detected by either one of the PCR primers used in ST from 42 patients with RA and 39 patients with OA. However, 5 of 15 SF samples from ReA patients were PCR positive. The sensitivity of GC‐MS to detect muramic acid was 2 pg/injected amount (227 pg muramic acid/mg ST), and that of the pan‐bacterial PCR was 2–20 bacteria colony forming units/reaction.

Conclusion

These results indicate that a bacterial component, muramic acid, is detectable by GC‐MS in ST from a few patients with advanced RA or OA. However, no bacterial DNA was detectable by PCR.