History of Microbiology

These flashcards cover key terms and concepts related to the history of microbiology, including significant figures, principles, and discoveries.

Spontaneous Generation

The belief that living organisms could arise spontaneously from nonliving matter

Biogenesis

The theory that living cells arise only from preexisting living cells

Aseptic Technique

Procedures that prevent contamination by unwanted microorganisms.

Germ Theory of Disease

The theory that microorganisms can cause disease.

What were some of the key discoveries related to the germ theory of disease? Who made these key discoveries?

• Agostino Bassi proved a silkworm disease caused by a fungus 

• Pasteur discovered a protozoan infection of silkworm

• Joseph Lister treated surgical wounds with a phenol solution reducing infection and proving that microorganisms cause surgical wound infections 

• Robert Koch proved that bacteria cause disease by culturing bacteria on nutrients and injecting samples into healthy animals then collecting blood samples from them to compare with the originally isolated bacteria finding that the 2 sets of blood has the same bacteria

Antonie van Leeuwenhoek

• Amateur scientist

• Lens maker

• Invented the 1st microscope

• Observed “animalcules”

• Dutch merchant

Francisco Redi

Hypothesis: maggots do not spontaneously generate from rotting meat

Experiment: open jars with meat exposed to air and files, sealed jars of meat, gauze covered jars with meat

Results: meat not covered = maggots, meat sealed = no maggots, meat with mesh = no maggots

Conclusion: disproved spontaneous generation

Criticisms: sealed jars blocked vital force, the secret sauce, air

Alternative explanations: large animals might not spontaneously generate but microorganism do

John Needham

Hypothesis: microorganisms spontaneously generate

Experiment: boiled broth to kill live microorganisms, poured into flasks, and sealed them

Results: broth became cloudy after a few days

Conclusion: supported spontaneous generation

Criticisms: broth had not been boiled long enough

Alternative explanations: flasks were contaminated while transferring before sealing = flawed experiment

Lazzare Spallanzani

Hypothesis: microorganisms came from the air

Experiment: 

• Repeated Needham’s experiment with stricter controls 

• Placed broth in flasks, boiled them longer, and sealed the flasks with no transfer 

Results: 

• Microorganisms in unsealed flasks 

• No microorganisms in sealed flasks 

Conclusions: disproved spontaneous generation

Criticisms and alternative explanations: 

• Vital source was killed by heat and kept out by the stopper

• Not enough oxygen

Louis Pasteur

Hypothesis: microorganisms arise from microbes in the air, biogenesis 

Experiment: 

• Developed S shaped swan neck flask 

• Boiled broth inside the flask

• The curve allowed air to reach the broth but dust and particles got trapped in the curve 

Results: broth remained sterile and clear free of microorganisms 

Conclusions: supported by experiment disproving spontaneous generation and supporting biogenesis 

Criticisms and alternative explanations:

• Still criticized so flask was tipped so that sterile broth came in contact with bacteria and dust causing microorganisms to grow 

What were the contributions of Louis Pasteur to microbiology?

• Disproved spontaneous generation

• Proved biogenesis: living cells arise only from preexisting living cells

• Fermentation: microorganisms convert sugar to alcohol and carbon dioxide in the absence of oxygen

• Pasteurization: heat kills bacteria that causes spoilage 

• Vaccines: discovered why vaccines work

Robert Koch

German physician

Played a major role in establishing that microorganisms cause specific diseases

Established Koch’s Postulates

What are Koch’s postulates?

A sequence of experimental steps for directly relating a specific microbe to a disease

Koch’s postulates:

1. Organisms must always be found associated with the disease state but NOT in a healthy host

2. Organism must be isolated and grown in a pure culture in the lab 

3. Organisms grown in pure culture must cause the same disease when inoculated into a healthy susceptible host 

4. Organism must be reisolated from the inoculated host, and shown to be the same as the other originally isolated organism

How do Koch’s postulates apply to cows with anthrax?

• Cows were dying 

• Koch collected dead cow’s blood, observed it under a microscope consistently finding Bacillus anthracis present in diseased but not healthy cows 

• Injected a healthy cow with a sample of blood from a sick cow leading to illness and death in the cow

• Koch repeated the procedure and always got the same results 

• Koch cultivated the microorganism in fluids outside the cow’s body and showed with the same results that a specific infectious disease is caused by a specific microorganism 

What are the exceptions to Koch’s postulates?

• Some microbes are difficult to culture because they have unique culture requirement and are unable to be cultured in a lab

• Some diseases can involve several microbes that cause the same signs and symptoms making it difficult to know which microorganism is causing the disease 

• Some pathogens can cause several diseases 

• Some microorganisms only cause disease in humans and have no other host posing an ethical question of whether humans can be intentionally inoculated with infectious diseases 

• Some hosts are just carriers of the disease and don’t show symptoms

What have been some contributions of microbiology to world civilization?

• Food production through fermentation

• Food preservation through pasteurization

• Disease treatment through antibiotics

• Disease prevention through aseptic technique and vaccines

What have been some contributions of microbiology to biochemistry and molecular biology?

• Much of our knowledge about biology was first discovered in bacteria 

• E. Coli is simple to grow, fast growing, cheap, and shares the chemistry of humans it is widely used 

• DNA as genetic material

• The Central Dogma: DNA to RNA transcription and RNA to protein translation

• CRISPR-Cas9

What are some different types of laboratories and what do they do?

• Hospital laboratories: tests carried out on clinical specimens that help identify 

  • diagnosis 

  • treatment

• Research laboratories: tests out on clinical and nonclinical specimens help identify 

  • new diagnosis methods

  • new treatments

  • basic understanding of microbiology

Fermentation

The microbial conversion of sugars into alcohol or acids.

Vaccination

The administration of a vaccine to promote immunity against a disease.

Cell theory

• All organisms are made of cells

• The cell is the most basic unit of life

• Cells come from preexisting cells

What is a disease?

A state different from homeostasis

What is the difference between a pathogen and a disease?

Pathogen causes disease