6 Matching Annotations
  1. Dec 2022
    1. Crystal violet, CV. In the aqueous solution created, CV exists as its cation CV+. CV+ ions penetrate the cell wall of the bacteria. CV+ binds to negative moieties of the peptidoglycan cell wall. Iodine is added. CV and I- complex and crystallise.

      Decolorization, the variable step, strips off the outer membrane of gram negative, but not gram positive bacteria. As the cell wall in gram negative becomes permeable, CVI diffuses out an colour is lost. <br /> Gram positive retains colour from CVI stain.

      Safarin is a positively charged counterstain. Binds colourless membrane of gram negative.

      Results in pink gram negative and purple gram positive.

    2. The Gram stain procedure is a differential staining procedure that involves multiple steps.

      Gram staining allows for the differentiation of gram positive and gram negative bacteria.

    1. In the early 1900s, the German physician and scientist Paul Ehrlich (1854–1915) set out to discover or synthesize chemical compounds capable of killing infectious microbes without harming the patient.
      • Ehrlich's magic bullet.
      • Salvarsan brought to market in 1910.
      • The systematic selection of compounds, informed by the specific causative agent, still used at present to bring new antibiotics today.
    1. Alexander Fleming: In 1928 Alexander Fleming observed antibiosis against bacteria by a fungus of the genus Penicillium and postulated the effect was mediated by an antibacterial compound, penicillin, and that its antibacterial properties could be exploited for chemotherapy.

      Fleming's serendipitous discovery of penicillin.

    1. certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation
    2. The theory of spontaneous generation states that life arose from nonliving matter. It was a long-held belief dating back to Aristotle and the ancient Greeks.
      • In addition, the Egyptians noted that the yearly river Nile mud gave rise to many frogs so they concluded that this mud spontaneously generated frogs.