- •Describe how to prepare a wet mount slide «The crushed drop» from liquid and agar microbic cultures.
- •1. Obtain a clean microscope slide.
- •What is the main technology of preparing the stains for determination of the morphology of microorganisms. What are the sizes and main shapes of the bacteria?
- •What kind of dye is used in microbiology? Name the methods of staining.
- •Types of Dyes
- •Ziehl-Neelsen Stain
- •India Ink
- •Methylene Blue Stain
- •Sketch a picture of the microorganism.
- •Sign the picture and specify Total Magnification (tm).
- •Gram Stain
- •4)What is the reason of using Gram staining? Describe this method of staining.
- •How Gram negative and Gram positive bacteria are looked like after Gram staining? Explain it.
- •How to distangushing Gram positive and Gram negative bacteria if you don’t have dyes and microscope? Describe this method and explain it.
- •Period 1
- •Period 2
- •What are the differences between slimy layer and capsule of bacteria? Capsules are considered protective structures. Various functions have been attributed to capsules including: ….
- •Biofilms – strategy of a survival of bacteria in environment. Characterize structure of biofilms. Explain the increased resistance of bacteria in biofilms.
- •Background
- •Results
- •Conclusion
- •Characterize spirochete. What features of their morphology and structure of cells. The habitat and representatives.
- •Classification
- •Spirochetes
- •12. Describe the methods Endospore (Spore) staining. Ozheshko method.
- •Explain the high resistance of bacterial endospores to unfavorable factors.
- •Characterize anaerobic spiral Gram- bacterium. What features of their morphology and structure of cells. The habitat and representatives.
- •Characterize sliding bacteria. What features of their morphology and structure of cells. The habitat and representatives.
- •Characterize budding bacteria. What features of their morphology and structure of cells. The habitat and representatives.
- •Characterize mycobacteria and nokardia forms. What features of their morphology and structure of cells. The habitat and representatives.
- •Characterize actinomycetes. What features of their morphology and structure of cells. The habitat and representatives.
- •What are the molecular and structural differences between archaea and eubacteria? Give a detailed response.
- •Bacterial Genome is consisted from 2 subsystems. Name and describe them. What properties of the cells are carried by plasmids.
- •Describe the internal structures of prokaryotic cell. Cytosol and Cytoplasm. Nonmembranous organelles: Ribosomes, Mesosomes. Nucleoid.
- •Bacteria can form specialized, morphologically differentiated structures. Describe them.
- •1. High molecular weight dna must bind to the cell surface.
- •2. The bound dna is taken up through the cell membrane.
- •3. The donor dna fragment is then integrated into the host chromosome or replicates autonomously as a plasmid.
- •Unlike eukaryote no true sexual reproduction is found in bacteria because: …. What are the features of the bacterial recombination
- •What are the functions of homologous associations of bacteria? Provide examples of homologous associations of bacteria.
- •Biochemical Tests: Microbiologists also use biochemical tests, noting a particular microbe's ability to utilize or produce certain chemicals.
- •What do the terms: pure culture, species, strain, clone in microbiology? What are the differential characteristics of the species?
- •What classification systems of microorganisms were offered before? Presents the modern classification system.
What kind of dye is used in microbiology? Name the methods of staining.
What is the reason of using them?
Types of Dyes
Not all specimens can be clearly seen under a microscope. Sometimes the specimen blends with other objects in the background because they absorb and reflect approximately the same light waves. You can enhance the appearance of a specimen by using a stain. A stain is used to contrast the specimen from the background.
A stain is a chemical that adheres to structures of the microorganism and in effect dyes the microorganism so the microorganism can be easily seen under a microscope. Stains used in microbiology are either basic or acidic.
Basic stains are cationic and have positive charge. Common basic stains are methylene blue, crystal violet, safranin, and malachite green. These are ideal for staining chromosomes and the cell membranes of many bacteria.
Acid stains are anionic and have a negative charge. Common acidic stains are eosin and picric acid. Acidic stains are used to stain cytoplasmic material and organelles or inclusions.
There are two types of Stains: simple and differential. A simply stain has a single basic dye that is used to show shapes of cells and the structures within a cell. Methylene blue, safranin, carbolfuchsin and crystal violet are common simple stains that are found in most microbiology laboratories.
Dyes used as biological stains are typically organic salts comprising a colored ion and an uncolored ion. In a basic dye, the colored organic ion is positively charged, so it's drawn toward negatively charged substances. The cytoplasm of bacterial cells tends to soak up basic dyes. Acidic dyes, by contrast, contain a negatively charged organic ion that the bacterium's surface repels; these dyes tend to stain around the organism, creating a colored background against which the bacterium is transparent. Other dyes, like India ink, are pH-neutral.
Ziehl-Neelsen Stain
Due to the composition of their cell walls, some dyed bacteria are "acid-fast," meaning that they will not lose their color if exposed to a dilute acid. Mycobacterium tuberculosis, the bacterium that causes tuberculosis, is a prominent example. Staining a specimen with carbol fuchsin dye while heating it, decolorizing the sample with an acid, and then counterstaining it with another dye will reveal whether acid-fast bacteria are present. This procedure is called the Ziehl-Neelsen stain.
India Ink
This technique involves suspending microbes in saline solution, and then staining them with India ink. Under the microscope, the India ink is very dark; if a microbe has a gelatinous capsule, it will stand out plainly against this background. This is known as a negative stain, because rather than coloring the microbe, it colors the microbe's surroundings on the slide. This technique is particularly useful when working with certain fungi, especially Cryptococcus neoformans.