COLOURING OF MICROORGANISMS

From Big Medical Encyclopedia

COLOURING OF MICROORGANISMS — the way of identification of microorganisms used at microbiological diagnosis of infectious diseases and for studying of morphology of microorganisms by means of microscopy in visible light.

The lake of m treats the cytochemical reactions happening between components of a microbe and dye. All dyes used for O. by m can be divided into two groups: the main and acid. The main dyes contain the painting cation and colourless anion, acid consist of the painting anion and a colourless cation. The main dyes are most active. It is caused by the fact that in usual environments of a bacterium bear negative surface-bound charge, and in them substances of the acid nature contain (DNA and RNA).

As the painting part of the main dyes bears positive charge, this type of dyes has big affinity to structures of a microbic cell, than acid, to-rye are capable to paint a cell only at low pH values. At usual pH values acid dyes are poorly fixed by a cell and easily are removed from it during the washing. Therefore acid dyes are used at so-called negative coloring when the background of drug is painted, on Krom uncolored bacteria are visible. Except acid and the main, there are so-called neutral dyes representing mix of acid and main dyes, in a cut the cation and anion have the painting properties. Therefore, such dye is capable to paint the cellular elements which are characterized both by an acidophilia, and a basophilia. An example of neutral dye is Gimza's paint applied to coloring of spirochetes and protozoa. It should be noted that proteinaceous structures of a cell under one conditions can be painted acid, and at others — the main dyes that is caused by amphoteric character of proteins, i.e. their ability to behave as acids or the bases depending on pH of the environment. Acid or osnovny character of water solution of dye can be determined by test with filter paper, the negative charge has edges. At use of the main dye its positively charged molecules will be fixed by particles of paper and water will climb paper in the form of a colourless strip. Acid dyes, moving together with water, will paint paper.

Methods O. of m in the drugs fixed thermal or chemical in the ways are most eurysynusic (see. Bacteriological techniques ). The purpose of fixing is disinfecting of drug and an attachment of bacteria to the surface of microscope slide. Thermal fixing (fixing by heat on a flame of a torch) apply to studying of morphology of microorganisms and endogenous a dispute. The X imichesky fixing (fixing by means of methyl alcohol, alcohol, Nikiforov's liquid, etc.) is applied to coloring of separate structures of microorganisms — flagellums, cytoplasm and a kernel of a cell.

Methods of coloring of the fixed drugs are subdivided on simple and difficult. Carry ways of coloring to the first group one main dye (methylene blue, methyl violet, osnovny fuchsin, etc.). At the same time all elements of drug (a cell of fabric, various bacteria) are painted in one color. Difficult methods of coloring consist of several stages of chemical or physical treatment of drugs using different dyes. Using these methods, it is possible to differentiate one microorganisms from others, to identify separate elements within a bacterial cell, and also to distinguish a cellular or fabric background of drug from the bacteria which are contained in it.

Difficult methods O. of m are widely used at identification of microorganisms. From these methods were widely adopted Grama method (see), Tsilya-Nelsena method (see), Romanovsky — Gimza a method (see). Use of coloring across Gram allows to divide conditionally all bacteria on gram-positive and gram-negative depending on whether bacteria are steady against the decolouring effect of acetone, alcohol or aniline oil after coloring by their dyes of perifenil-metane group (gentsianovy violet, crystal violet, methyl violet) and processings of drug iodine.

During the coloring by Tsil's method — Nelsen is differentiated by acid resisting bacteria from kislotopodatlivy. This method is applied at mikrobiol, diagnosis of tuberculosis. Acid resistance of mycobacteria of tuberculosis is caused by the high content in them of lipids, fat to - t and polyatomic alcohol. One of lipids which is constantly found in acid resisting bacteria and keeping acid resistance in the look isolated from cells is mikolovy to - that. However the sign of acid resistance at bacteria revealed by coloring by Tsil's method — Nelsena, is lost if to subject cells to stress rupture or a lysis. Acid resistance, therefore, is caused by structural integrity of a cell, the maintenance in it of lipids and, perhaps, their specific topology in bacteria.

Various methods O. of m use also for studying of structures of a microbe. Osmic to - that apply to coloring of inclusions of fat, iodine for identification of starch, polychrome-ny methylene blue to coloring of grains of volutin etc. Use of ink at O. the m allows to find the capsule in bacteria (see. Burri a method , Ginsa method ). A classical method of identification of biochemical differentiated structures of a microbe is Feylgen's method — Rossenbeka (see. Deoxyribonucleic acid ), allowing to define existence in a bacterium of DNA. By means of this method it was established that bacteria contain the Nucleoids which are equivalents of kernels of cells of the higher organisms.

Except the listed methods O. of m, there is a way of identification of microbes based on ability nek-ry of them to recover salts of heavy metals. The most known is impregnation of microorganisms silver nitride, a cut is recovered by a microbic cell, giving it dark coloring. This way was applied to identification of spirochetes (see. Levaditi method ) and for diagnosis of smallpox by detection in the studied material of little bodies of Pashen (see. Morozova method ).

See also Histologic methods of a research .



Bibliography: Meynel Dzh. and Meynel E. Experimental microbiology, the lane with English, page 174, M., 1967; The Guide to microbiological diagnosis of infectious diseases, under the editorship of K. I. Matveev, page 27, M., 1973; The Reference book on microbiological and virologic methods of a research, under the editorship of M. O. Birger, page 22, M., 1973; T and m and-kov V. D. and D. M Goldfarb. Fundamentals of experimental medical bacteriology, page 100, M., 1958; G i 1-lies R. a. Dodds T. Bacteriology illustrated, Edinburgh — L., 1976.


L. A. Zamchuk.

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