Dark field microscopy enhances the contrast of transparent and unstained specimens by illuminating them with light that does not enter the objective lens unless it is scattered by the specimen. This creates a bright image of the specimen against a dark background, making normally invisible structures visible. Procedure for Dark Field Microscopy Preparation of the … Read more
Principle of Transmission Electron Microscopy Transmission Electron Microscopy works by transmitting a beam of electrons through an ultra-thin specimen. As electrons interact with the specimen, the transmitted electrons form an image. Due to the short wavelength of electrons, TEM can resolve details as small as 0.1 nm, making it suitable for studying cellular ultrastructure and … Read more
Cultivation of Anaerobes requires special techniques to create and maintain oxygen-free environments. Anaerobes are microorganisms that grow in the absence of oxygen. Two common methods for cultivating anaerobes are the candle jar method and the GasPak jar method. Candle Jar Method Description: A simple and inexpensive method to create a microaerophilic (low oxygen) environment. Procedure: … Read more
Preserving pure cultures is essential for maintaining bacterial viability and genetic stability over extended periods. Common preservation methods include: Refrigeration of Preservation Methods for Pure Cultures Temperature: 4°C Duration: Short-term storage (weeks to months). Procedure: Cultures are stored on agar slants or in broth media in a refrigerator. Advantages: Simple and easy for short-term use. … Read more
Isolation Methods of pure cultures involves separating a single species of microorganism from a mixed population. Common methods include: Streak Plate Method: Procedure: A sterile inoculating loop is used to spread a diluted sample over the surface of an agar plate in a series of streaks. Purpose: To separate individual cells to form isolated colonies. … Read more
Nutritional Requirements of Bacteria is like all living organisms, require a variety of nutrients to grow and reproduce. These nutrients can be categorized into macronutrients and micronutrients. Macronutrients: Macronutrients are nutrients needed in large amounts for energy and growth—carbohydrates, proteins, and fats. Carbon: Fundamental for cellular structure and energy. Sources include carbohydrates, lipids, proteins, and … Read more
Optimal bacterial growth depends on key physical parameters such as temperature, pH, oxygen levels, and moisture, each varying by species. Temperature required for bacterial growth: Bacteria have different optimal temperature ranges for growth: Psychrophiles: Grow at low temperatures (0-20°C). Mesophiles: Grow at moderate temperatures (20-45°C), including most human pathogens. Thermophiles: Grow at high temperatures (45-80°C). … Read more
Raw Materials Used for Culture Media are essential for growing, isolating, and identifying microorganisms in the laboratory. The composition of these media can vary depending on the specific requirements of the microorganisms being cultured. Here are some of the common raw materials used in the preparation of culture media: Basic Components of Raw Materials Used … Read more
The bacterial growth curve represents the growth of a bacterial population over time in a closed system (batch culture). It has four distinct phases: Lag Phase: Bacteria adapt to new environment. Metabolic activity is high, but cell division is minimal. Synthesis of enzymes, proteins, and other molecules needed for growth. Log (Exponential) Phase: Rapid cell … Read more
Morphological Classification of Bacteria is based on their morphology (shape), arrangement, staining properties, and other characteristics. Here are the main types of morphological classification: Based on Shape: Cocci: Spherical bacteria. Diplococci: Pairs of cocci (e.g., Neisseria). Streptococci: Chains of cocci (e.g., Streptococcus). Staphylococci: Clusters of cocci (e.g., Staphylococcus). Tetrads: Groups of four cocci (e.g., Micrococcus). … Read more
