Whole bacteria detection

Notwithstanding the aforementioned difficulty in detecting specific target proteins other than the types normally observed in the taxonomic fingerprints from whole bacteria MALDI spectra (i.e., ribosomal proteins), some other target proteins and protein-like materials have been studied directly from whole cells. For example, Lantibiotics, antimicrobial peptides secreted by Gram-positive bacteria have been detected directly from whole bacteria by MALDI-TOF MS.51 The lantibiotics nisin and lacticin 481 were detected from whole cells and crude supernatants. Surprisingly, better results were reported from whole cells than the supernatants. In this study the presence of variants... 

Hindre, T. Didelot, S. Le Pennec, J.-P Haras, D. Dufour, A. Vallee-Rehel, K. Bacteriocin detection from whole bacteria by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Appl. Environ. Microbiol. 2003, 69,1051-1058. 

As the typical molecule in Gram-negative bacteria, lipid A can be used to detect the bacteria. Detection methods need to be rapid and sensitive therefore, a few rapid methods for lipid A micro-extraction from whole bacteria have been developed. 

Protein sensing involves detection of the protein component of the pathogenic bacteria, viruses, and individnal toxins. It requires minimal sample preparation. Specificity is achieved by using antibodies, receptors, or aptamers raised or selected to specifically bind surface proteins or whole bacteria, bacterial spores, viral particles, or individual toxins. 

This method detects and differentiates four bacterial species using Py-IT-MS by using unique lipid profiles (generated by creating FAMEs) of whole bacteria with a total analysis time of 10 min/Upid profiles. Py-TOF-MS can be used to analyze powder samples and rapidly identify hoax material compounds [88]. The powdered... 

The identification of whole virus and bacteria is important for fast and precise infection determination, as well as for identifying potentially risky areas and contaminated equipment in health centers, avoiding hospital-acquired infections. POC devices have been envisioned as great opportunities for whole organism detections mainly due to their simple preparation, avoiding the typical steps of virus isolation, extraction. 

Lebaron, P. Catala, P. Fajon, C. Joux, F. Baudart, J. Bernard, L. A new sensitive, whole-cell hybridization technique for detection of bacteria involving a biotinylated oligonucleotide probe targeting rRNA and tyramide signal amplification. Appl. Environ. Microbiol. 1997, 63, 3274-3278. 

As noted above, whole-cell MALDI-TOF MS was intended for rapid taxonomic identification of bacteria. Neither the analysis of specific targeted bacterial proteins, nor the discovery of new proteins, was envisioned as a routine application for which whole cells would be used. An unknown or target protein might not have the abundance or proton affinity to facilitate its detection from such a complex mixture containing literally thousands of other proteins. Thus, for many applications, the analysis of proteins from chromatographically separated fractions remains a more productive approach. From a historical perspective, whole-cell MALDI is a logical extension of MALDI analysis of isolated cellular proteins. After all, purified proteins can be obtained from bacteria after different levels of purification. Differences in method often reflect how much purification is done prior to analysis. With whole-cell MALDI the answer is literally none. Some methods attempt to combine the benefits of the rapid whole cell approach with a minimal level of sample preparation, often based on the analysis of crude fractions rather... 

The most common criticism of whole-cell MALDI is that the method requires a relatively large number of cells, usually obtained directly from culture media. In principle, an analysis of even a few unknown bacteria (a colony-forming unit) is possible after a culture step. More important is the number of bacteria needed in a sample or on the sample probe for successful analysis. Detection of a very small number of bacteria could eliminate the need for a preliminary culture step. This would be a considerable asset for environmental analysis (unless to many bacteria were detected) and for the detection of a bioterrorism-related release of bacteria. 

Madonna, A. I Basile, F. Imma, I. Meetani, A. M. Rees, J. C. Voorhees, K. J. On-probe sample pretreatment for the detection of proteins above 15 KDa from whole cell bacteria by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Rapid Comm. Mass Spectrom. 2000,14, 2220-2229. 

Wall, D. B. Lubman, D. M. Flynn, S. J. Rapid profiling of induced proteins in bacteria using MALDI-TOF mass spectrometric detection of nonporous RP HPLC-separated whole cell lysates. Anal. Chem. 1999, 71,3894-3900. 

An interesting imaging probe Id that can selectively target bacteria was recently reported by Smith et al. [31] also based on a heptamethine chromophore. The probe is composed of a bacterial affinity group, which is a synthetic zinc (II) coordination complex that targets the anionic surfaces of bacterial cells and a near infrared dye. The probe allowed detection of Staphylococcus aureus in a mouse leg infection model using whole animal near-infrared fluorescence imaging. 

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