Saran's Learn Microbiology

  GAS VACUOLES ·        Gas vacuole, a structure that provides buoyancy to some aquatic Prokaryotes. ·        Gas vacuoles are present in many Photosynthetic bacteria and a few other Aquatic prokaryotes such as Halobacterium (a salt-loving archaeon) and Thiothrix (a filamentous bacterium). GAS VESICLES ·        Gas vacuoles are aggregates of enormous numbers of Small, Hollow, Cylindrical or Conical shaped structures called Gas vesicles. ·        Gas vesicles in different species vary in length from about 300 to more than 1000 nm and in width from 45 to 120 nm. ·        Gas vesicles may number from a few to hundreds per cell. ·        Gas vesicle walls are composed entirely of two small Protein sub-units (Major protein – Gvp A and Minor protein – Gvp C). These protein sub-units assemble to form a rigid enclosed cylinder that is hollow and impermeable to water but freely permeable to atmospheric gases. Functions of Gas Vesicles ·        Aquatic Prokaryotes with Gas ve

  NUCLEOID —   The Nucleoid of a bacterial cell usually contains a single long, continuous, and frequently circularly arranged thread of Double stranded DNA called the Bacterial Chromosome. —   The Nucleoid can be spherical, elongated, or dumbbell shaped. —   Nucleoid carries all the genetic information required for the cell’s structures and functions. —   Unlike the Chromosomes of Eukaryotic cells, Bacterial Chromosomes are not surrounded by a Nuclear envelope (membrane) and do not include histones. —   The nucleoid can also be seen under a Light microscope by staining it with the Feulgen stain, which specifically stains DNA. —   The DNA-intercalating stains DAPI (4 ′ ,6-diamidino-2-phenylindole) and Ethidium bromide are widely used for Fluorescence Microscopy of Nucleoids. —   Experimental evidence suggests that the Nucleoid is largely composed of about 60 % DNA, plus a small amount of RNA (mRNA) and Protein (Transcription Factor Proteins) for regulating the bacterial g

  ENDOSPORES ·       Endospores are the resisting non-reproductive structures formed by bacteria for survival during adverse environmental condition. ·        Endospores were first discovered by John Tyndall. He discovered the heat resistant Endospores of bacteria which survived after heating at 100 °C. ·        Endospores can be variable in size and location within the cell. ·        Endospores are structurally, metabolically and functionally different from the Vegetative cells. ·      The completed endospore consists of multiple layers of resistant coats (including a cortex, a spore coat, and sometimes an exosporium) surrounding a nucleoid, some ribosomes, RNA molecules, and enzymes. ·        Endospores are commonly found in soil and water, where they may survive for long periods of time. STRUCTURE OF ENDOSPORES Bacterial Endospore (Source: www.easybiologyclass.com) ·        The structure of Endospore is very compl