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
Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University
How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy