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?
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. There are two ways to prepare a specimen to be observed under a light compound microscope. These are a wet mount and a smear. A wet mount is a preparation process where a live specimen in culture fluid is placed on a concave glass side or a plain glass slide. The microorganism is free to move about within the fluid, although the viscosity of the substance slows its movement. This makes it easier for you to observe the microorganism. The specimen and the substance are protected from spillage and outside contaminates by a glass cover that is placed over the concave portion of the slide. A smear is a preparation process where a specimen that is spread on a slide. You prepare a smear using the heat fixation process. For most staining procedures one need only air dry the film by holding the slide high above a bunsen flame, when dry pass the slide film side up, three times through the flame to kill and fix the cells. Too much heat will distort the shape of the organism and could alter its uptake of stain - the slide should feel warm but not hot. Bear in mind that staining procedures kill the cells and that some of the cells characteristics may inevitably be altered. All stainings are to be carried out over the staining rack or in the sinks.
Bacteria constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most habitats on the planet, growing in soil, water, acidic hot springs, radioactive waste, and deep in the Earth's crust, as well as in organic matter and the live bodies of plants and animals, providing outstanding examples of mutualism in the digestive tracts of humans, termites and cockroaches. Most bacteria are 0.2 um in diameter and 2-8 um in length.
The three most common bacterial cell shapes are cocci(spherical, from the Greek word for seed/berry), bacilli (rod-shaped, from the Greek word for staff), and spirilla(curved shape, from spiral). There are various ways of subdividing these three overarching shapes mostly based on how they are arranged into multicellular organizations.
Coccus (plural cocci or coccuses) can be used to describe any bacterium that has a spherical shape. It is one of the three distinct types of bacteria shapes, the other two being bacillus (rod-shaped) and spirillum (spiral-shaped) cells. Coccus is an English loanword of a Neolatin noun, which in turn stems from the Greek masculine noun kokkos (κόκκος) meaning "berry".
The term 'coccus' is used in botany to denote a mericarp or 1-seeded segment of a schizocarp.
Arrangement Like all bacteria, each single coccus bacterium is an entire living organism. And some species exist in groups of cells. If they do group together, the patterns they arrange themselves in are given certain names based on the shape. Diplococci are arranged in two-cell pairs; these may represent several different genera. Bacteria in the Streptococcus genus are arranged in chains. Bacteria in the Sarcina genus typically form a cuboidal arrangement of eight cells. Staphylococcus is a genus of bacteria characterized by cells arranged in tetrad clusters (four cells in a square formation) or large, often irregular, clusters. While groups of cells together form these characteristic shapes, the individual bacterial cells themselves will appear as distinct circles within the chain or cluster.
Cocci may be oval, elongated, or flattened on one side.
Cocci may remain attached after cell division. These group characteristics are often used to help identify certain cocci.
Cocci that remain in pairs after dividing are called diplococci.
Cocci that remain in chains after dividing are called streptococci.
Cocci that divide in two planes and remain in groups of four are called tetrads.
Cocci that divide in three planes and remain in groups cube like groups of eight are called sarcinae
Cocci that divide in multiple planes and form grape like clusters or sheets are called staphylococci.
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the phylum Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species. Under stressful environmental conditions, the cells produce oval endospores that can stay dormant for extended periods. These characteristics originally defined the genus, but not all such species are closely related, and many have been moved to other genera.
Most bacilli appear as single rods. Diplobacilli appear in pairs after division.
Streptobacilli appear in chains after division.
Some bacilli are so short and fat that they look like cocci and are referred to as coccobacilli.
Spiral bacteria
Spiral bacteria have one or more twists.
Vibrios look like curved rods.
Spirilla have a helical shape and fairly rigid bodies.
Spirochetes have a helical shape and flexible bodies. Spirochetes move by means of axial filaments, which look like flagella contained beneath a flexible external sheath.
