Characterization of Clostridium species utilizing liquid chromatography/mass spectrometry of intact proteins

Proteome-Based Serotyping of the Food-Borne Pathogens Salmonella Enterica by Label-Free Mass Spectrometry

Food-borne diseases caused by Salmonella enterica of 2500 serovars represent a serious public health problem worldwide. A quick identification for the pathogen serovars is critical for controlling food pollution and disease spreading. Here, we applied a mass spectrum-based proteomic profiling for identifying five epidemiologically important Salmonella enterica subsp. enterica serovars (Enteritidis, Typhimurium, London, Rissen and Derby) in China. By label-free analysis, the 53 most variable serovar-related peptides, which were almost all enzymes related to nucleoside phosphate and energy metabolism, were screened as potential peptide biomarkers, and based on which a C5.0 predicted model for Salmonella enterica serotyping with four predictor peptides was generated with the accuracy of 94.12%. In comparison to the classic gene patterns by PFGE analysis, the high-throughput proteomic fingerprints were also effective to determine the genotypic similarity among Salmonella enteric isolates according to each strain of proteome profiling, which is indicative of the potential breakout of food contamination. Generally, the proteomic dissection on Salmonella enteric serovars provides a novel insight and real-time monitoring of food-borne pathogens.

Selective Capture and Identification of Methicillin-Resistant Staphylococcus aureus by Combining Aptamer-Modified Magnetic Nanoparticles and Mass Spectrometry

A nucleic acid aptamer that specifically recognizes methicillin-resistant Staphylococcus aureus (MRSA) has been immobilized on magnetic nanoparticles to capture the target bacteria prior to mass spectrometry analysis. After the MRSA species were captured, they were further eluted from the nanoparticles and identified using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). The combination of aptamer-based capture/enrichment and MS analysis of microorganisms took advantage of the selectivity of both techniques and should enhance the accuracy of MRSA identification. The capture and elution efficiencies for MRSA were optimized by examining factors such as incubation time, temperature, and elution solvents. The aptamer-modified magnetic nanoparticles showed a capture rate of more than 90% under the optimized condition, whereas the capture rates were less than 11% for non-target bacteria. The as-prepared nanoparticles exhibited only a 5% decrease in the capture rate and a 9% decrease in the elution rate after 10 successive cycles of utilization. Most importantly, the aptamer-modified nanoparticles revealed an excellent selectivity towards MRSA in bacterial mixtures. The capture of MRSA at a concentration of 10² CFU/mL remained at a good percentage of 82% even when the other two species were at 10⁴ times higher concentration (10⁶ CFU/mL). Further, the eluted MRSA bacteria were successfully identified using MALDI mass spectrometry.

Identification of bacteria in juice/lettuce using magnetic nanoparticles and selected reaction monitoring mass spectrometry

Ensuring food safety requires a rapid and reliable method for detecting food-borne pathogens. Mass spectrometry has been demonstrated as a powerful tool to classify pure bacterial species. However, matrix interference from food backgrounds may lead to false results because of the suppression of microbial signals. It is useful to develop a method for bacterial enrichment and marker identification in food samples. Magnetic zirconia nanoparticles were used to concentrate spiked microorganisms from apple juice/lettuce under specific conditions (pH 4.5). Bacterial identification was achieved using nanoLC-MS. Selected reaction monitoring of bacteria-related peptides was applied for the first time to identify bacteria including Staphylococcus aureus and Escherichia coli. This study presents an accurate means for bacterial identification in food matrixes using MS. The analysis time is less than 90 min and the minimum concentration of E. coli detected was 5 × 103 CFU/mL. The interaction between bacteria and the magnetic nanoparticles was electrostatic and nonspecific, in contrast to immunoassays which require specific antibodies. The targeted peptide analysis focuses on the bacterial markers, thus significantly simplifying the analysis and leading to an accurate identification of bacteria.

Progress of electrospray ionization and rapid evaporative ionization mass spectrometric techniques for the broad-range identification of microorganisms

Electrospray ionization and rapid evaporative ionization mass spectrometric techniques have attracted much attention in the identification of microorganisms, and in the diagnosis of bacterial infections from clinical samples.

Proteomic Methods of Detection and Quantification of Protein Toxins

Biological toxins are a heterogeneous group of compounds that share commonalities with biological and chemical agents. Among them, protein toxins represent a considerable, diverse set. They cover a broad range of molecular weights from less than 1000 Da to more than 150 kDa. This review aims to compare conventional detection methods of protein toxins such as in vitro bioassays with proteomic methods, including immunoassays and mass spectrometry-based techniques and their combination. Special emphasis is given to toxins falling into a group of selected agents, according to the Centers for Disease Control and Prevention, such as Staphylococcal enterotoxins, Bacillus anthracis toxins, Clostridium botulinum toxins, Clostridium perfringens epsilon toxin, ricin from Ricinus communis, Abrin from Abrus precatorius or control of trade in dual-use items in the European Union, including lesser known protein toxins such as Viscumin from Viscum album. The analysis of protein toxins and monitoring for biological threats, i.e., the deliberate spread of infectious microorganisms or toxins through water, food, or the air, requires rapid and reliable methods for the early identification of these agents.

Protein identification in two phases of 1,3-propanediol production by proteomic analysis

Proteomic analysis by two-dimensional electrophoresis (2D)-mass spectrometry was used to identify differentially expressed proteins in the Clostridium sp. native strain (IBUN 158B) in two phases of the 1,3-propanediol (1,3-PD) production (lag phase and exponential growth phase). Intracellular protein fraction extraction conditions were standardised, as well as the 2D electrophoresis. Differences were found between both of the growth phases evaluated here. Thirty-two of the differentially expressed proteins were chosen to be identified by tandem mass spectrometry (MALDI TOF/TOF). The presence of four enzymes implicated in the 1,3-PD metabolic pathway was recorded: one from the reductive route (1,3-propanediol dehydrogenase) and three from the oxidative route (3-hydroxybutyryl-CoA dehydrogenase, NADPH-dependent butanol dehydrogenase and phosphate butyryl transferase). The following enzymes which have not been previously reported for Clostridium sp., were also identified: phosphoglycerate kinase, glucose 6-phosphate isomerase, deoxyribose phosphate aldolase, transketolase, cysteine synthetase, O-acetylhomoserine sulphhydrylase, glycyl-tRNA ligase, aspartate-β-semialdehyde dehydrogenase, inosine-5-monophosphate dehydrogenase, aconitate hydratase and the PrsA protein. The foregoing provides a novel contribution towards knowledge of the native strain for the purpose of designing genetic manipulation strategies to obtain strains with high production of 1,3-PD.

BIOLOGICAL SIGNIFICANCE

The article "Protein identification in two phases of 1,3-propanediol production by proteomic analysis" provides a novel contribution towards knowledge regarding the Colombian Clostridium sp. native strain (IBUN 158B) because this is a new approximation in comparative proteomics in two phases of the bacterial growth and 1,3-propanediol (1,3-PD) production conditions. The proteomic studies are very important to identify the enzymes that are expressed at different stages of production and therefore genes of interest in the genetic manipulation strategies; the results can be taken into account in future studies in metabolic engineering when optimising 1,3-PD production, in a cost-effective process having direct industrial applications.

Advances in mass spectrometry for the identification of pathogens

Mass spectrometry (MS) has become an important technique to identify microbial biomarkers. The rapid and accurate MS identification of microorganisms without any extensive pretreatment of samples is now possible. This review summarizes MS methods that are currently utilized in microbial analyses. Affinity methods are effective to clean, enrich, and investigate microorganisms from complex matrices. Functionalized magnetic nanoparticles might concentrate traces of target microorganisms from sample solutions. Therefore, nanoparticle-based techniques have a favorable detection limit. MS coupled with various chromatographic techniques, such as liquid chromatography and capillary electrophoresis, reduces the complexity of microbial biomarkers and yields reliable results. The direct analysis of whole pathogenic microbial cells with matrix-assisted laser desorption/ionization MS without sample separation reveals specific biomarkers for taxonomy, and has the advantages of simplicity, rapidity, and high-throughput measurements. The MS detection of polymerase chain reaction (PCR)-amplified microbial nucleic acids provides an alternative to biomarker analysis. This review will conclude with some current applications of MS in the identification of pathogens.