Microbiology Lab Techniques Quiz

Microbiology and Parasitology (Laboratory)

• BIOL 014 is a course offered by the Polytechnic University of the Philippines, College of Science, Department of Biology.
• The course covers laboratory discussions on various topics, including microscopy, slide preparations, different types of microscopes, micrometry, and staining techniques.
• Microscopy allows the study of living organisms and species not visible to the naked eye.
  • Sir Antonie van Leeuwenhoek invented the first microscope using a single lens, magnifiying 300x.
  • Later, double lens microscopes were invented in the late 16th century.
• Different types of microscopes exist.
  • Bright-field microscopes produce a dark image against a brighter background, having multiple objective lenses.
  • Dark-field microscopes produce a bright image against a dark background, useful for viewing unstained living cells.
  • Phase-contrast microscopes enhance contrast and allow viewing of internal cellular components and examining growth of living cells.
  • Fluorescence microscopes use ultraviolet, violet, or blue light to view samples stained with fluorochromes; showing bright images of objects from fluorescent light.
  • Electron microscopes use electrons, having high energy, to examine very fine objects at a very fine scale (transmission and scanning types).
• Micrometry is the science of measuring specimen dimensions.
  • Stage and ocular micrometers are used, with the stage micrometer being calibrated.
• Slide preparations (wet mount, hanging drop, staining) involves specific procedures to observe cell activities (motility, binary fission), natural sizes, and cell shapes
• Gram staining is a differential staining procedure to distinguish Gram-positive and Gram-negative bacteria based on cell wall structures.
  • Gram-positive bacteria have thick cell walls with peptidoglycan.
  • Gram-negative bacteria have thin cell walls with a second lipid membrane called lipopolysaccharides.
• Biochemical assays are used to detect, quantify, or study microbial biochemical activities, aiding in identifying microbial species, their metabolic pathways, and roles in different environments.
• Oxygen requirements of microorganisms are used to classify them (aerobes, obligate, facultative, microaerophilic, aerotolerant, and anaerobes).
• Aseptic techniques are critical for avoiding contamination in microbiological procedures.
• Cultural characteristics involving observations of colony size, shape, pigmentation, opacity, and surface features and growth rate of colonies and other aspects of pure and mixed cultures are also observed through the use of various media and other apparatuses.
• Several techniques for isolating microorganisms are available such as serial dilution, streak method, pour plate, and spread plate
• Antibiotic assays that involve dilution and diffusion assays are used to measure the effectiveness of various antibiotic types on microbial strains as well as the factors like genetic mutations that affect antibiotic resistance.
• Standard plate count method is used for estimating the population density of bacteria in a broth based on valid counts (bacteria 25-250, and molds 10-150).
• Various types of culture media are examined in relation to their consistency, nutritional ingredients and functional use (liquid, solid and semi-solid, simple, complex, chemically defined media, enriched, selective, differential, and transport media).
• Different assays are explained through chemical and or media components used for testing bacterial species (catalase test, urea test, gelatin hydrolysis tests, and lipid hydrolysis tests) including media type and temperatures used
• Laboratory activities include procedures to isolate fungi from spoiled fruits and vegetables to examine samples using the appropriate technique (macroscopic and microscopic examination, including use of stain like lactophenol cotton blue).