Lab Act 3

• Microbiology is the study of biological entities too small to be seen with the naked eye
• Biological entities studied in microbiology

  • Algae
  • Bacteria
  • Fungi
  • Protozoa
  • Viruses
• The majority of microorganisms is unicellular and exhibit apparent structural and organizational simplicity
• General morphological shapes of bacteria

  • Rod
  • Coccus
  • Spiral
• Rod-shaped bacteria

  • Also referred to as bacilli, can be found occasionally in pairs (diplobacilli) and in chains (streptobacilli)
• Spherical or coccus forms

  • Pairs of bacteria (Diplococci)
  • Chains of 4 or more cells (streptococci)
  • Four bacteria in a square arrangement (tetrads)
  • Irregular groups of bacterial cells resembling grape clusters (staphylococci)
  • 8 cocci grouped into a cuboidal packet (sarcinae formation)
• Coiled or spiral-shaped bacteria

  • Spirochetes consist of flexible, wavering forms with several coils
  • Spirilla are rigid bacteria possessing one or several curves
  • Short spiral forms that do not form complete coils are called vibrio
• Structural components of a prokaryotic or bacterial cell

  • Nucleoid (DNA)
  • Ribosomes
  • Cell membrane
  • Cell wall
  • Surface layer
• Architectural regions of a bacterial cell

  • Appendages (attachments to the cell surface) in the form of flagella and pili (fimbriae)
  • Cell envelope consisting of a capsule, cell wall, and plasma membrane
  • Cytoplasmic region containing the cell chromosome (DNA) and ribosomes and various sorts of inclusion
• Flagella


  Long, whip-like structures that allow bacteria to move and navigate towards favorable environments
• Pili


  Short, hair-like structures used for conjugation (transferring genetic material between bacteria) and attachment to surfaces
• Fimbriae


  Hair-like appendages similar to pili, but shorter and more numerous. They primarily aid in attachment to surfaces and other cells
• Capsule


  A slimy, gel-like layer outside the cell wall that provides protection from drying out, phagocytosis (being engulfed by immune cells), and harsh environments
• Cell wall


  A rigid outer layer made of peptidoglycan that provides shape, support, and protection
• Plasma membrane


  A selectively permeable membrane that regulates the passage of materials into and out of the cell
• Cytoplasm


  A jelly-like substance inside the cell that contains dissolved nutrients, enzymes, and other molecules needed for cellular functions
• Ribosome


  Cellular structures responsible for protein synthesis
• Nucleoid


  The region within the cytoplasm where the bacterial chromosome (circular DNA) is located