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• Microbiology


  Study of organisms that individually are too small to be seen by the naked eye. Study of microorganisms, a large and diverse group of microscopic organisms that exist as single cells or cell clusters; it also includes viruses, which are microscopic but not cellular.
• In microbiology, we are studying about bacteria, fungi, viruses, and parasites that can be observed under the microscope. These microorganisms can cause disease to humans and there are some microorganisms that we consider as commensal which means they cannot cause any harm even if they're inside our body.
• Roman Philosopher Lucretius and Girolamo Fracastoro suggested that a disease was caused by "invisible living creature".
• Francesco Stelluti made the earliest microscopic observations on weevils using a microscope probably supplied by Galileo.
• Anton Van Leeuwenhoek


  The first true microbiologist. The first person to observe and describe microorganisms accurately. He discovered animalcules. He used his self-made single lens microscope with 50-300x magnification.
• Aristotle believed that simpler invertebrates could arise from spontaneous generation.
• Francesco Redi demonstrated in 1668 that maggots do not arise spontaneously from decaying meat. His results were a serious blow to the long-held belief that large forms of life could arise from non-life.
• John Needham observed that boiled mutton broth (tightly sealed) eventually became cloudy with microorganisms. He proposed that organic matter possessed a vital force that could give rise to life.
• Lazzaro Spallanzi improved the previous experiments of Needham by using sealed boiled water and seeds. He observed that no growth took place as long as the flasks remained sealed.
• Biogenesis


  Living cells can rise only from preexisting living cells.
• Rudolf Virchow challenged spontaneous generation with the concept of biogenesis.
• Theodore Schwann observed that no growth occurred in a flask containing nutrient solution after allowing air to pass through a red-hot tube.
• Goerg Friedrich Schroder and Theodore von Dusch observed that no growth occurred after allowing air to pass through sterile cotton wool placed in a flask of heat-sterilized medium.
• Shwann, Schroder and Dusch observed that upon application of heat, there will be no presence of growth in bacteria. They believe that application of heat can lead to killing the bacteria or can be used as a sterilizing agent.
• Louis Pasteur


  He resolved the issue of spontaneous generation. He stated that microorganisms are indeed present in the air and can contaminate seemingly sterile solutions, however the air itself does not create microbes. He showed that microorganisms can be present in non-living matter (fomites). He started that microbial life can be destroyed by heat (basis of the aseptic technique). He provided evidence that microorganisms cannot originate from mystical forces present in nonliving materials.
• John Tyndall showed that dust carry germs which contaminates sterile broth. Tyndallization is a form of sterilization for three consecutive days.
• Theodore Schwann stated that yeast cells were responsible for the conversion of sugars to alcohol, however he said that fermentation was not due to microorganisms but to a chemical instability that converted sugars to alcohol.
• Pasteur described that certain microorganisms known as "yeast" converts sugar to alcohol in the absence of air (fermentation). Souring and spoilage are caused by different microorganisms called bacteria. In the presence of air, bacteria change the alcohol in the beverage into vinegar (acetic acid). Heating the beer and wine just enough to kill most of the bacteria (pasteurization).
• Pasteur's Contribution to Science


  • He disproved the theory of spontaneous generation.
  • He developed vaccines against anthrax (1881) and rabies (1885).
  • He improved the wine industry (theory of fermentation).
• Charles Chamberland created a porcelain bacterial filter (1884) and developed anthrax vaccine together with Pasteur.
• The Germ Theory of Disease


  Microorganisms might cause the disease.
• John Lister developed the antiseptic system of surgery. He demonstrated the used of phenol for treating surgical wounds and also sprayed phenol over the surgical area. The main contribution of Lister in the field of surgery is the application of phenol as a type of wound sterilizer or an aseptic technique in the wound.
• Robert Koch's Contributions


  • He established the first proof that bacteria cause disease.
  • He discovered Bacillus anthracis – causative agent of anthrax.
  • He discovered Mycobacterium tuberculosis.
  • He was the first to culture bacteria on boiled potatoes, gelatin and used meat extracts and protein digests for cultivation.
  • He developed culture media for observing growth of bacteria isolated from human body.
• Koch's Postulates


  • The microorganisms must be present in every case of the disease but absent from healthy organisms.
  • The suspected microorganisms must be isolated and grown in a pure culture.
  • The same disease must result when the isolated microorganisms is inoculated into healthy host.
  • The same organisms must be isolated again from the diseased host.
• Collaboration of Koch


  • Fannie Eilshemius Hesse suggested the use of agar as a solidifying agent.
  • Richard Petri developed the petri dish (plate).
  • Martinus Beijernick and Sergie Winogradsky developed the enrichment-culture technique and the use of selective media.
• Edward Jenner experimented on how people can be protected against small pox. He collected scrapings from cowpox blisters and inoculated a healthy volunteer with the cowpox material by scratching the person's arm with a pox-contaminated needle.
• Pasteur used the term "vaccine" – for culture of a virulent microorganisms use for preventive inoculation. He used attenuated culture known as vaccine (Latin "vacca" – cow).
• Chemotherapy


  Is the treatment of disease by using chemical substances. It also refers to chemical treatment of noninfectious diseases, such as cancer.
• Types of Chemotherapy


  • Synthetic drugs - Prepared from chemicals in the laboratory.
  • Antibiotics - Produced naturally by bacteria and fungi to act against microorganisms.
• Emil Von Behring prepared antitoxins for diphtheria and tetanus.
• Paul Ehrlich discovered salvarsan (arsphenamine) for treatment of syphilis.
• Alexander Fleming accidentally discovered penicillin (Penicillum notatum).
• Howard Florey and Ernst Chain made the purification process for penicillin.
• Dr. Abelardo B. Aguilar, an ilonggo physician, discovered the antibiotic erythromycin in soil samples he obtained but never got the credit and compensation he truly deserved.
• Prokaryotes


  "Pro" meaning before and "karyon" meaning nucleus, nut or kernel. These are organisms that do not contain a true nucleus surrounded by nuclear membrane, characteristics of lower forms such as bacteria. They do not contain organelles and all functions take place in the cytoplasm or cytoplasmic membrane.
• Cell Envelope


  Outermost structure composed of outer membrane and periplasm (gram negative only), cell wall and plasma membrane.
• Cell Wall


  Also referred to as peptidoglycan or murein layer. It is composed of disaccharide-pentapeptide subunits; also made up of teichoic acid or lipoteichoic acid. Is a rigid structure that maintains the shape of the cell. Major function: To prevent bacterial cells from rupturing when the osmotic pressure inside the cell is greater than outside the cell. It also serves as a point of anchorage for flagella. Its synthesis and structures have been the primary target of antimicrobial agents.
• Gram Positive Cell Wall

  Composed of a very thick protective, peptidoglycan (murein) layer. Consists of glycan chains of alternating N-acetyl-D-glucosamine and N-acetyl-D-muramic acid. Teichoic acid is negatively charged and contributes to the negativity of the cell wall; t may also bind and regulate the movement of cations into and out of the cell. Penicillin acts by preventing the synthesis of peptidoglycan.
• Gram Negative Cell Wall

  Composed of outer and inner (thin peptidoglycan) membranes. Outer membrane – proteins, phospholipids and lipopolysaccharide. Lipid A – major constituent; toxic. Core polysaccharide. Antigenic O – specific polysaccharide. LPS have the following important function: They are vitals in evading the host defense. They contribute to the negative charge of the bacterial surface, which stabilizes the membrane structure. LPS considered as an endotoxin.
• Comparison of Gram Positive and Gram Negative Bacteria

  • Cell Wall: Gram positive - The thick cell wall is composed of peptidoglycan and teichoic acids may also be present. Gram negative - The outer membrane is composed of lipids, proteins, LPS, and thin inner peptidoglycan layer.
  • Shape: Gram positive - Spherical, rod-shaped or filamentous. Gram negative - Spherical, oval, straight or curved rods, helical or filamentous.
  • Metabolism: Gram positive - Chemoorganoheterotrophic. Gram negative - Phototrophic, Chemolithoautotrophic, Chemoorganoheterotrophic.
  • Teichoic Acid: Gram positive - Present. Gram negative - Absent.
  • Endospore: Gram positive - Present in some. Gram negative - Absent.
  • Periplasmic Space: Gram positive - Absent. Gram negative - Present.
  • Flagellar Structure: Gram positive - 2 rings in the basal body. Gram negative - 4 rings in the basal body.
  • Resistance to physical disruption: Gram positive - High. Gram negative - Low.
  • Resistance to lysozyme: Gram positive - Low. Gram negative - High.
  • Inhibition by basic dye: Gram positive - High. Gram negative - Low.
  • Reproduction: Gram positive and Gram negative - Binary fission.