MANI'S MICROBIOLOGY

  Ø   A spectrophotometer is an instrument that measures the amount of light absorbed by a sample. Ø   It measures the concentration of solutes in the solution by measuring the amount of light that is absorbed by the solution in a cuvette placed in the spectrophotometer. Ø   The photometer measures the amount of light that passes through the sample and delivers a voltage signal to the display. Principle Ø    Beer-Lambert Law states that there is a linear relationship between the absorbance and the concentration of a sample. Ø    A=ϵlc Where, o     A is the measure of absorbance (no units), o    ϵ is the molar extinction coefficient or molar absorptivity (or absorption coefficient), o    l is the path length, and o    c is the concentration. Basic parts or instrumentation Ø   The basic spectrophotometer ins...

  ·        Colorimeter is a device used in colorimetry ·        It means measurement of absorbance at particular wavelengths of light. ·        It means the quantity/ concentration of substance present in a liquid sample. ·        Widely used in biological sample analysis.   Principle ·        It works by the Beer–Lambert law.  ·        The absorption of light transmitted through the solution is directly proportional to the solution concentration. ·        This is done by passing light of a  specific wavelength of the visible spectrum through the solution in a photoelectric colorimeter instrument and observing the galvanometric reading of reflection sensitizing the quantity of light absorbed. ·      I t = I o X e -kc...

  v   Viruses are the smallest infectious particles, first described as the “filterable agents” discovered in 1898. v   Russian bacteriologist Dimitri Iwanowski filtered the sap of diseased plants through a porcelain filter that was designed to retain bacteria. v   Their small size allows them to pass through filters designed to retain bacteria. v   Martinus Willem Beijerinck called the filtered, infectious substance a “virus”, calling his discovery a  'contagium vivum fluidum ' v   Martinus Beijerinck  is often called the Father of Virology. v   1904–08 V. Ellermann, O. Bang, H. Vallee, H. Carre first demonstrated a leukemia-causing retrovirus. v   Viruses are not living, obligate intracellular parasites, requiring host cells for replication. v   Ranging in diameter from 18 to 1500 nanometres. v   Requires Electron microscope for visualization, cannot be seen with a light microscope. v   Viruses typic...