- •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.
Period 1
Inoculate each bacterial culture into a separate tube of the semisolid Motility Medium.
Use the needle and carefully stab-inoculate the medium about half-way down through the center.
The wire is then pulled out of the media as close as possible to the location where it entered.
The tube is incubated for approximately 1-2 days at 30 °C and observed for evidence of motility.
Period 2
Observe the tubes of Motility Medium for growth away from the line of inoculation and the subsequent cloudiness throughout the medium as discussed in the introduction. In a well-lit room, hold all of the tubes together against a darker part of the ceiling (such as the space between the fluorescent light units) so that degrees of growth can be discerned easily. Ignore all surface growth and any growth that might be creeping down from the surface along the inner wall of the tube.
What are the differences between slimy layer and capsule of bacteria? Capsules are considered protective structures. Various functions have been attributed to capsules including: ….
When the composition of this layer is tightly bound and remains attached to cells, it is referred to as a capsule.
More loosely bound layers that are difficult to see are termed slime layers.
Many bacterial cells secrete some extracellular material in the form of a capsule or a slime layer. A slime layer is loosely associated with the bacterium and can be easily washed off, whereas a capsule is attached tightly to the bacterium and has definite boundaries. Capsules can be seen under a light microscope by placing the cells in a suspension of India ink. The capsules exclude the ink and appear as clear halos surrounding the bacterial cells. Capsules are usually polymers of simple sugars (polysaccharides), although the capsule of Bacillus anthracis is made of polyglutamic acid. Most capsules are hydrophilic (“water-loving”) and may help the bacterium avoid desiccation (dehydration) by preventing water loss. Capsules can protect a bacterial cell from ingestion and destruction by white blood cells (phagocytosis). While the exact mechanism for escaping phagocytosis is unclear, it may occur because capsules make bacterial surface components more slippery, helping the bacterium to escape engulfment by phagocytic cells. The presence of a capsule in Streptococcus pneumoniae is the most important factor in its ability to cause pneumonia. Mutant strains of S. pneumoniae that have lost the ability to form a capsule are readily taken up by white blood cells and do not cause disease. The association of virulence and capsule formation is also found in many other species of bacteria.
A capsular layer of extracellular polysaccharide material can enclose many bacteria into a biofilm and serves many functions. Streptococcus mutans, which causes dental caries, splits the sucrose in food and uses one of the sugars to build its capsule, which sticks tightly to the tooth. The bacteria that are trapped in the capsule use the other sugar to fuel their metabolism and produce a strong acid (lactic acid) that attacks the tooth enamel. When Pseudomonas aeruginosa colonizes the lungs of persons with cystic fibrosis, it produces a thick capsular polymer of alginic acid that contributes to the difficulty of eradicating the bacterium. Bacteria of the genus Zoogloea secrete fibres of cellulose that enmesh the bacteria into a floc that floats on the surface of liquid and keeps the bacteria exposed to air, a requirement for the metabolism of this genus. A few rod-shaped bacteria, such as Sphaerotilus, secrete long chemically complex tubular sheaths that enclose substantial numbers of the bacteria. The sheaths of these and many other environmental bacteria can become encrusted with iron or manganese oxides. Capsules are considered protective structures. Various functions have been attributed to capsules including:
1) Adherence to surface, tissue or substrate in nature.
2) Capsules also often play a role in pathogenicity acting as virulence factors to protect cells from phagocytosis and/or complement-mediated killing.
3) Protect cells from perennial effects of drying or desiccation.
4) Capsular materials (e.g. dextrans) may be overproduced when bacteria are fed sugars to become reserves of carbohydrate for subsequent metabolism.
5) Important plant pathogens such as strains of Pseudomonas, Rhizobium, and Erwinia require capsules for pathogenicity.
Capsules are characterized by poor staining with standard dyes. Capsule staining methods thus depend upon revealing the presence of the capsule indirectly. Often capsule staining methods are accomplished using a combination of the following: (i) a basic dye that interacts with the negative ions of the bacterial cell, (ii) a mordant that causes the precipitation of the capsular material, e.g., metal ions, alcohol, and acetic acid (9), and (iii) an acidic stain used to color the background.
At the completion of the preparation, the capsule is revealed as a clear halo between the colored background and the stained cell. In some capsule staining preparations, cells are exposed to antibody against capsular antigens to enlarge the capsule for easier visualization