Biologists in History

Hooke

reported that living things were composed of little boxes, or cells

Leeuwenhoek

described live microorganisms that he observed in teeth scrapings, rain water, and peppercorn infusions.

Biogenesis support

• Louis Pasteur demonstrated that microorganisms are present in the air

• He had two flasks, one with heated nutrient broth that was sealed, and one with nutrient broth that was unsealed.

• The sealed flask had no microbial growth, suggesting that microbes don’t come from nothing

• The unsealed flask had growth, suggesting microbes are already present in the air

• Pasteur also has S-shaped flasks that he bent in such a way that air could still enter but microbes could not. The heated and cooled broth was left in the flasks for months with no signs of microbial growth, further proving his theory. (The bend in the necks trapped any microbes that may have entered in the air)

Needham

• first to suggest spontaneous generation by finding that broth boiled, cooled, and placed into covered flasks was soon teeming with microorganisms

• claimed that the “vital force” necessary for spontaneous generation was destroyed by heat applied to the flask after sealing it, shutting down Spallanzani’s theory of biogenesis

Spallanzani

• suggested microbes from the air had entered Needham’s flasks during his experiments for spontaneous generation

• he proved this by showing that broth heated after they were already sealed in flasks did not have any microbial growth

Virchow

• challenged the case for spontaneous generation with the concept of biogenesis, hypothesizing that living cells arise only from preexisting living cells.

• Wasn’t proven until a few years later by Pasteur

Pasteur

• proving biogenesis (with the experiment)

• fermentation (converting sugar to alcohol in the absence of air) and pasteurization: Pasteur discovered that bacteria are responsible for fermentation and food spoilage.

• He demonstrated that heating wine just long enough to kill the bacteria without evaporating the alcohol. This process was applied to many other things and called Pasteurization.

Lister

• used a chemical disinfectant to prevent surgical wound infections after looking at Pasteur’s work showing microbes are in the air, can spoil food, and cause animal diseases

• proved that microorganisms can cause surgical wound infections

Koch

• provided proof that a bacterium causes anthrax and provided the experimental steps, Koch’s postulates, used to prove that a specific microbe causes a specific disease.

• was Pasteur’s rival in the race to discover the cause of Anthrax and provided the first real proof that bacteria caused disease.

Koch’s postulates

• Association: The suspected pathogen must be found in all cases of the disease and absent from healthy subjects.

• Isolation: The pathogen must be isolated from the diseased host and grown in pure culture.

• Inoculation: A healthy, susceptible host infected with the cultured pathogen must develop the same signs and symptoms of the disease.

• Re-isolation: The pathogen must be re-isolated from the new host and shown to be identical to the original pathogen

Jenner

Vaccinations and Immunity:

• Observation: Dairymaids who had mild cowpox infections

  were protected from smallpox

  Hypothesis: Cowpox infection provides protection against

  smallpox

  Experiment (1798): Inoculated boy with cowpox fluid and

  later challenged with smallpox fluid

  Result: Boy did not get smallpox

  Called vaccination from vacca for cow

Ehrlich

• jumpstarted the idea for modern chemotherapy by developing a synthetic arsenic drug, salvarsan, to treat syphilis.

• came up with the “Magic Bullet” which could hunt down and destroy a pathogen without harming the infected host.

Fleming

• Discovered the first antibiotic, Penicillin

• noticed that some culture plates contaminated by mold had a clear area where bacterial growth had been inhibited encircling the mold.

• Became what know as Penicillin, and he used it to kill S. aureus.

• Today, it’s used to kill many types of bacteria