Gram stain or Gram staining called Gram's method, is a method of staining used to distinguish and classify bacterial species into two large groups. The name comes from the Danish bacteriologist Hans Christian Gram. Gram staining differentiates bacteria by the physical properties of their cell walls. Gram-positive cells have a thick layer of peptidoglycan in the cell wall that retains the primary stain, crystal violet. Gram-negative cells have a thinner peptidoglycan layer that allows the crystal violet to wash out on addition of ethanol, they are stained pink or red by the counterstain safranin or fuchsine. Lugol's iodine solution is always added after addition of crystal violet to strengthen the bonds of the stain with the cell membrane; the Gram staining is always the first step in the preliminary identification of a bacterial organism. While Gram staining is a valuable diagnostic tool in both clinical and research settings, not all bacteria can be definitively classified by this technique; this gives rise to gram-indeterminate groups.
The method is named after its inventor, the Danish scientist Hans Christian Gram, who developed the technique while working with Carl Friedländer in the morgue of the city hospital in Berlin in 1884. Gram devised his technique not for the purpose of distinguishing one type of bacterium from another but to make bacteria more visible in stained sections of lung tissue, he published his method in 1884, included in his short report the observation that the typhus bacillus did not retain the stain. Gram staining is a bacteriological laboratory technique used to differentiate bacterial species into two large groups based on the physical properties of their cell walls. Gram staining is not used to classify archaea archaeabacteria, since these microorganisms yield varying responses that do not follow their phylogenetic groups; the Gram stain is not an infallible tool for diagnosis, identification, or phylogeny, it is of limited use in environmental microbiology. It is used to make a preliminary morphologic identification or to establish that there are significant numbers of bacteria in a clinical specimen.
It cannot identify bacteria to the species level, for most medical conditions, it should not be used as the sole method of bacterial identification. In clinical microbiology laboratories, it is used in combination with other traditional and molecular techniques to identify bacteria; some organisms are gram-variable. In a modern environmental or molecular microbiology lab, most identification is done using genetic sequences and other molecular techniques, which are far more specific and informative than differential staining. Gram staining has been suggested to be as effective a diagnostic tool as PCR in one primary research report regarding gonococcal urethritis. Gram stains are performed on body biopsy when infection is suspected. Gram stains yield results much more than culturing, is important when infection would make an important difference in the patient's treatment and prognosis. Gram-positive bacteria have a thick mesh-like cell wall made of peptidoglycan, as a result are stained purple by crystal violet, whereas gram-negative bacteria have a thinner layer, so do not retain the purple stain and are counter-stained pink by safranin.
There are four basic steps of the Gram stain: Applying a primary stain to a heat-fixed smear of a bacterial culture. Heat fixation kills some bacteria but is used to affix the bacteria to the slide so that they don't rinse out during the staining procedure; the addition of iodide, which binds to crystal violet and traps it in the cell Rapid decolorization with ethanol or acetone Counterstaining with safranin. Carbol fuchsin is sometimes substituted for safranin since it more intensely stains anaerobic bacteria, but it is less used as a counterstain. Crystal violet dissociates in aqueous solutions into chloride ions; these ions penetrate the cell wall of both gram-negative cells. The CV+ ion interacts with negatively charged components of bacterial cells and stains the cells purple. Iodide interacts with CV+ and forms large complexes of crystal violet and iodine within the inner and outer layers of the cell. Iodine is referred to as a mordant, but is a trapping agent that prevents the removal of the CV–I complex and, colors the cell.
When a decolorizer such as alcohol or acetone is added, it interacts with the lipids of the cell membrane. A gram-negative cell loses its outer lipopolysaccharide membrane, the inner peptidoglycan layer is left exposed; the CV–I complexes are washed from the gram-negative cell along with the outer membrane. In contrast, a gram-positive cell becomes dehydrated from an ethanol treatment; the large CV–I complexes become trapped within the gram-positive cell due to the multilayered nature of its peptidoglycan. The decolorization step must be timed correctly. After decolorization, the gram-positive cell remains purple and the gram-negative cell loses its purple color. Counterstain, positively charged safranin or basic fuchsine, is applied last to give decolorized gram-negative bacteria a pink or red color. Both gra
Johann Melchior Dinglinger was one of Europe's greatest goldsmiths, whose major works for the elector of Saxony, Augustus the Strong, survived in the Grünes Gewölbe, Dresden. Dinglinger was the last goldsmith to work on the grand scale of Benvenuto Cellini and Wenzel Jamnitzer, fewer of whose large-scale works in precious materials have survived, however, his work carries on in a Mannerist tradition into the "Age of Rococo". Dinglinger was born in Biberach an der Riß, he served his apprenticeship in Ulm, after which he refined his techniques working as a journeyman in Augsburg and Vienna, three traditional centers of luxury arts. He went to Dresden in 1692, where he spent the rest of his career in the service of Augustus, by whom he was appointed court jeweller in 1698. In the workshop he established, he was assisted by his younger brothers, the enameller Georg Friedrich Dinglinger and Georg Christoph Dinglinger, who specialized in cutting and setting jewels; the sculptor Balthasar Permoser collaborated as a modeller in Dinglinger's workshops.
Dinglinger's sister Sophie was an artist. Dinglinger had twenty-three children, of whom eleven survived to maturity; the famous house he erected in Dresden was burned in the Seven Years' War. He died in Dresden. Dinglinger's major works, all for Augustus: 1697–1701 The Golden Coffee Service, which presents the cups and saucers and sugar bowls on an elaborate pyramidal etagère surmounted by the coffeepot, all in enamelled gold, a kabinettstuck unique in Europe. Augustus took the completed ensemble with him to Warsaw at Christmas 1701, to dazzle the nobles of the Polish-Lithuanian Commonwealth of which he was the nominal ruler; the Birthday of the Grand Mogul Aurangzeb, with 137 modelled enamelled and jewel-encrusted figures of men and animals, which Dinglinger commenced without a specific commission, sold to the delighted Elector for a spectacular 55,485 thaler. The invasion of Saxony by Charles XII of Sweden made payments difficult and the greater part of the vast sum was owing until 1713. 1704 Dianabad, in which a chalcedony bowl in a filigree is supported between the horns of a stag's head.
1722 Obeliscus Augustalis Altar of Apis, an unusual example, for its generation, of Egyptianizing taste before 1722 Pair of agate standing cups celebrating the election of Augustus as King of Poland, mounted in gold, parcel gilt silver, semi-precious stones E. von Watzdorf, 1962. Johann Melchior Dinglinger Johann Melchior Dinglinger on-line Walters Art Museum: a cup by Dinglinger "Hofjuwelier Dinglinger"
Spy Hook is a 1988 spy novel by Len Deighton. It is the first novel in the second of three trilogies about Bernard Samson, a middle-aged and somewhat jaded intelligence officer working for the British Secret Intelligence Service. Spy Hook is part of the Hook and Sinker trilogy, being succeeded by Spy Line and Spy Sinker; this trilogy is preceded by the Game and Match trilogy and followed by the final Faith and Charity trilogy. Deighton's novel Winter is a prequel to the nine novels, covering the years 1900-1945 and providing the backstory to some of the characters; the novel begins with Bernard Sampson visiting his old friend and ex-SIS colleague in Washington named Jim Prettyman as part of an investigation regarding some missing funds. Soon after, Prettyman is murdered in a mugging. All his allies start losing interest in the investigation, after digging deeper Bernard is sent to America once again, where it is revealed that Bret has not indeed died but is in fact in rehabilitation. Bernard returns to Europe, where he confronts a man called "Dodo" and is saved from an untimely death by Prettyman, who it turns out has gone under "deep-cover".
Bernard takes his evidence to the Director General, who in a surprise turn of events orders his arrest, which thanks to some quick thinking by Werner Volkmann, Bernard evades for the while. The novel concludes with Bernard seeking an explanation from Frank Harrington, before disappearing into the night