Subscribe via

Lecture 1 & 2: A glimpse of Microbiology

How did Lineus categorized organisms?

He did so, under 3 principles:

1. Respiration & Nutrtion

2. Unicellular & Multicellula

3. Prokaryotes or Eukaryotes

Aside from Lineus, a few other important microbiologists were:

Antoni van Leeuwenhoek: created the microscope!

Aristotle: He theorized the idea of abiogenesis or spontaneous generation, which suggests living organisms are derived asexually, sexual reproduction, or from a nonliving thing.

Francesco Redi (Redi’s Experiment): who was an Italian physician looking at the decaying of meat and saw decaying meat, sealed and absent of flies showed no maggots; meanwhile, meat exposed to flies developed maggots on the meat. This experiment had scientists doubting dear Aristotle’s theory of abiogenesis.

John T. Needham: A British investigator who tightly sealed vials of boiled beef gravy and plant juice (steeping plants in water) with corks, showed a cloudy texture after a few days. He observed the growth of microorganisms must have been the parents of the cloudy stuff to come to life. Thus, he heated the vials and successfully killed off the microorganisms.

Lazzaro Spallanzani: contradicted Needham. He boiled the broth containing plant and animal materials for about an hour in sealed vials (melting the vials’ neck closed) and saw his broth clear. When the seal was broken, the broth turned cloudy. He suggested:

1. Needham heat his vials insufficiently to kill the microbes or he did not seal the vials tightly enough

2. microbes exists in air and may be contaminates

3. spontaneous generation of microbes does occur and all living things arise from other living things

Controversy arouse and Spallanzani’s experiments was challenged such as: insufficient air exposure preventing microbes to grow, and prolonged heating may have killed the microbes.

Louis Pasteur

Instead of sealing the flasks by melting the necks like Spallanzani, Pasteur bent the neck into a “S” form which allowed air to enter but not microbes into the broth since the microbes (from the air) would be stuck at the bottom of the bend. After sliding the broth to touch the bend of the flask, he noticed growth of microorganisms in the broth. Later, he broke all the flasks and saw that all broth exposed to air delivered microorganisms. He concluded that the microbes in the air caused the cloudiness.

Main points: disproved spontaneous generation, disprove cause of fermentation, used heat and boiling to sterilize (paterurization)

John Snow

He was a physician who introduced the miasma theory. He identified cholera, interviewed residences and saw patterns. He’s also very significant in epidemiology.

Joseph Lister

Lister used carbonic acid (HCO3-) as antiseptic for surgical instruments and introduced gloves in hospitals.


Established the cause of anthrax, which is caused by a rod shape bacillus producing endospores, and tuberclosis, which is caused by a rod-shape bacterium, Mycobacterium tuberculosis. Good for him to choose looking at anthrax since its fairly larger than other bacteria and was easier to see under the microscope at that time. He was successful and extremely influential in microbiology. Some of his accomplishments allowed the advancements in laboratory microbiology:

  1. simple staining techniques for bacterial cells and flagella
  2. first photomicrograph of bacteria (anthrax)
  3. first photograph of bacteria in diseased tissue
  4. techniques for estimating number of bacteria in a solution based upon number of colonies that form after inoculation onto a solid surface
  5. use of steam to sterilize growth media
  6. use of Petri dishes to hold solid growth media
  7. Aseptic laboratory techniques such as transferring bacteria between media using a platinum wire that had been heat sterilized with a flame
  8. elucidating bacteria as distinct species

Koch’s postulates – a series of steps must be taken to prove cause of a infectious disease

  1. Causing agent must be found in every case of disease and absent in the healthy hosts
  2. Agent must be isolated and grown outside the host.
  3. Healthy, susceptible host must get the disease when agent is introduced
  4. Same agent must be reisolated from the experimentally diseased host

Christian Gram

Introduced Gram’s staining which allows the identification of the peptidolycan component in Gram-positive microbes as purple, and pink in Gram-negative. This is the first differential stain that should be used in identifying a bacteria as either a Eubacteria (Gram +) and arcahea (gram -)

Leave a Reply