Gram staining of bacteria is a routine diagnostic method of long standing that can be used for initial diagnoses and to simplify the choice of antibiotics. It is a simple way to classify bacteria into two classes—Gram-positive and Gram-negative—under a microscope. In the journal Angewandte Chemie, American researchers have now introduced an improvement to this method: magnetic Gram staining. This allows for the class-specific, automated, magnetic detection and separation of bacteria.
Gram staining was developed about a hundred years ago by Danish bacteriologist Hans Christian Gram. In this technique, bacterial cultures are colored by a stain known as crystal violet, which enters into the murein layer of the bacterial cell walls. Treatment with an iodine-containing solution forms water-insoluble complexes between the crystal violet and iodine.
There are two classes of bacteria that differ in the structures of their cell walls. A thick murein layer surrounds one class; the others have only a thin one. Whereas subsequent treatment with ethanol dissolves the stain complex out of the thin murein layer, it remains firmly lodged in the thick murein layers. Bacteria whose stain can be washed away in this manner are classified as Gram-negative; those that remain dark purple are Gram-positive.
Scientists working with Ralph Weissleder at Harvard University in Boston (USA) have now developed Gram staining into a magnetic diagnostic technique. To achieve this, they attached a “molecular hook” to the molecules of crystal violet. With this modified dye, the staining process works just as it does with the original. After staining, however, “eyes” that correspond to the “hooks” are used to attach magnetic nanoparticles to the stain. This makes it easy to quantify the bacteria: nuclear magnetic resonance (NMR) instruments detect the magnetization of the nanoparticles.It is possible to take an NMR measurement before washing with ethanol to obtain the total number of Gram-positive and Gram-negative bacteria, and again after the washing step to determine the concentration of Gram-positive bacteria.
The advantage of this magnetic detection method is its high sensitivity. It is possible that samples could be directly magnetized and measured without prior purification or culture of the bacteria. By using the simple but sensitive miniaturized micro-NMR instruments developed by this research group, fast and sensitive on-the-spot diagnosis is conceivable. In addition, the magnetization could be used for the separation of bacteria from the sample.
Ralph Weissleder | Angewandte Chemie
Rising water temperatures could endanger the mating of many fish species
03.07.2020 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
Moss protein corrects genetic defects of other plants
03.07.2020 | Rheinische Friedrich-Wilhelms-Universität Bonn
Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.
Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....
Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.
Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...
A promising operating mode for the plasma of a future power plant has been developed at the ASDEX Upgrade fusion device at Max Planck Institute for Plasma...
Live event – July 1, 2020 - 11:00 to 11:45 (CET)
"Automation in Aerospace Industry @ Fraunhofer IFAM"
The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM l Stade is presenting its forward-looking R&D portfolio for the first time at...
With an X-ray experiment at the European Synchrotron ESRF in Grenoble (France), Empa researchers were able to demonstrate how well their real-time acoustic monitoring of laser weld seams works. With almost 90 percent reliability, they detected the formation of unwanted pores that impair the quality of weld seams. Thanks to a special evaluation method based on artificial intelligence (AI), the detection process is completed in just 70 milliseconds.
Laser welding is a process suitable for joining metals and thermoplastics. It has become particularly well established in highly automated production, for...
02.07.2020 | Event News
19.05.2020 | Event News
07.04.2020 | Event News
03.07.2020 | Life Sciences
03.07.2020 | Studies and Analyses
03.07.2020 | Power and Electrical Engineering