VMC 211: General Veterinary Microbiology (1+1)

CYTOPLASM

• It is the cell material surrounded by the cytoplasmic membrane. It may be divided into
  • Cytoplamic area – granular in appearance.
  • Chromatic area – rich in DNA.
  • The fluid portion with dissolved substances.
• In the cytoplasm some ribosomes are free while some especially those involved in synthesis of proteins to be transported out of the cell are associated with the inner surface of the cytoplasmic membrane. The sedimentation coefficient of the bacterial ribosomes is 70 S. It is made of 50 S and 30 S subunits. ( In eukaryotes - 80 S made of 60 S and 40 S subunits.)
• In some bacteria concentrated deposits of certain substances are found in the cytoplasm.
  
  • Volutin granules or metachromatic granules - They are composed of polyphosphate. They stain intense reddish purple with methylene blue. In electron microscopy they appear as round dark areas. They serve as reserve source of phosphate.
  • Poly beta hydroxybutyrate(PHB) granules - They are found in aerobic bacteria. They are made up of chloroform soluble lipid like material which can serve as a reserve of carbon and energy source. PHB granules can be stained with lipid soluble dyes such as Nile blue. In electron microscopy they appear as clear round areas.
  • Polysaccharide granules – They are made up of glycogen.The granule can be stained with iodine and appear brown in colour. In electron microscopy they appear as dark granules.
• Gas vacuoles are found in some bacteria living in aquatic habitats. They provide buoyancy. They appear as bright, retractile bodies in light microscope. In electron microscope they appear as hollow, rigid cylinders with more or less conical ends and have a striated protein boundary.
• Intra cellular globules of elemental sulphur are found in some bacteria growing in hydrogen sulphide rich environments.