Unit 1The Development of Microbiology

Do Now• What was the last illness you had?• How sick did you feel?• Do you know if it was caused by a

microorganism? Which one?

The Beginnings• Robert Hooke 1665:

• Introduced the world to small objects and creatures when he published his journal – Micrographie

• It contained illustrations of• Eye of a fly• Stinger of a bee• Shell of a protozoan• Plant-like mold• Cork cells

The Beginnings• Zacharias Janssen:

•Spectacle maker from the Netherlands

• Invented the microscope

The Beginnings• Anton van Leeuwenhoek 1670’s

• Seller of silk, wool, and cotton in the Netherlands

• Enhanced Jansenn’s microscope for use in his business

• But his fascination with the microscope led him to examine hair fibers, blood cells and even his own feces

The Beginnings• Anton van Leeuwenhoek (continued)

• Looked at marshy lake water which teemed with microorganisms – he called them animalcules

• He contacted the Royal Society of London and sent them letters and drawings of his studies

• But, he was very suspicious and didn’t let any one know how to make his lenses

• He also never made the connection between microorganisms and disease

The Transition Period• Biology of the 1700’s consisted of observations of plant

and animal life and attempts to classify them (Linnaeus)

• Scientists did not think of infection in terms of tiny living organisms

• Believed that an infectious disease spread by a miasma - an altered chemical quality of the atmosphere which arose from diseased bodies - miasmas

• This miasma theory was believed well into the 1800’s and gradually dissipated with the realization that microorganisms caused infectious disease

Do Now• 1. Who invented the microscope?• 2. Who improved or enhanced the

microscope?• 3. What is the name of the chemical

quality of the atmosphere that 1700’s scientists believed caused infectious disease?

Spontaneous Generation

• In the 1700’s many scientists believed that life comes from non-living things

• Living conditions - Why does meat get maggots?

• They come from the meat!• Francesco Redi did not agree with this

Spontaneous Generation

• REDI’S EXPERIMENT 1668

John Needham 1748• Needham agreed with spontaneous generation• He boiled bottles of broth (gravy) and said

heating would kill any organisms already in it• He then capped the bottles of broth – no air

could enter• After several days, the bottles were

contaminated with microorganisms• He concluded that they arose from the broth

and spontaneous generation does occur

LAZZARO SPALLAZANI b. 1729

• He knew about Redi and Needham’s experiments and he thought Needham was wrong

• So, Spallanzani did not believe in spontaneous generation

• What mistake do you think he thought Needham had made in his experiment?

LAZZARO SPALLAZANI b. 1729

• He thought Needham hadn’t boiled the broth enough

• He decided to run his own version of the experiment

• He thoroughly boiled the broth and stored some in an open container and some in a closed container

• After several days he saw……• No microorganisms in the sealed bottle, and

tons in the unsealed bottle

Spallanzani’s Experiment

LAZZARO SPALLAZANI b. 1729

• Microorganisms do not come from broth – non-life

• They come from the air!• If this were not so then both jars would

have organisms• But many still believed in Spontaneous

Generation – they said that it required oxygen and Spallanzani had blocked it out

Disease Transmission• People still believed the Miasma Theory of

infection because then people were not at fault for spreading disease

• In 1847 Ignaz Semmelweis, a Hungarian doctor, reported that the agent of blood poisoning was transmitted to maternity patients by doctors that had just performed autopsies

• He said that hand washing in chlorine water would stop the spread of disease – no one listened

Disease Transmission• John Snow, a British doctor traced the source of

an 1854 cholera epidemic to London’s municipal water supply

• He said that if people avoided the water, they would avoid the disease

• People listened and the spread of the disease was stopped

• These 2 doctors showed that disease was caused by an unseen object in the environment – not a miasma.

Do Now• 1. Briefly describe Francesco Redi’s

experiment. What was he trying to disprove?

• 2. Did John Needham agree with Redi?• 3. Briefly describe Lazzaro

Spallanzani’s experiment. What was his conclusion?

The Golden Age• The science of microbiology blossomed

for about 60 years, beginning in 1857• It began with a scientist named Louis

Pasteur and ended about the time of WWI

• Numerous branches of microbiology were established and the foundations for modern microbiology were laid down

Louis Pasteur’s World• In the 1800’s, the world was ravaged by

plague, tuberculosis, typhoid fever, and diphtheria.

• It was necessary to have a large family to ensure the next generation

• Even royalty could not avoid disease• No one was sure what caused disease –

no cures

Louis Pasteur - Fermentation

• Believed that scientific discoveries should have practical applications

• He wanted to find out why local wines were turning sour

• At the time people thought that wine fermentation resulted from the chemical breakdown of grape juice into wine.

• They didn’t know any living creatures were involved

Louis Pasteur – Fermentation

• But Pasteur’s microscope revealed large numbers of tiny yeast cells

• He correctly believed that the yeasts played a major role in fermentation

• In an experiment he removed all yeast from grape juice and it did not ferment

• Then he added the yeast back and it did ferment into wine

• He suggested that grape juice be heated to destroy all life before fermentation was begun - pasteurization

•

Louis Pasteur - Bacteria

• Pasteur also noticed that the sour wines contained tiny sticks and rods known as bacteria

• He did an experiment where he removed all bacteria from grape juice

• The when he mixed it with yeast it could ferment and not turn sour

Louis Pasteur – Germ Theory

• Pasteur’s discoveries shook the scientific community

• He demonstrated that yeast cells and bacteria were tiny living factories where important chemical changes were occurring

• He also showed microorganisms could be agents of change – they could cause a disease rather than being an effect of the disease

• Germ Theory of Disease – microorganisms are responsible for infectious diseases

LOUIS PASTEUR •People still believed in spontaneous generation!

•Pasteur decided to end the debate once and for all with an ingenious experiment

LOUIS PASTEUR

Pasteur’s Conclusion• He said that life comes from LIFE!• This is called Bio-genesis• Pasteur’s work brought to an end the

debate of spontaneous generation• Now scientists had to concentrate on

connecting certain microorganisms to specific diseases

Do Now• 1. What did Pasteur conclude was

causing the fermentation of grapes into wine?

• 2. What did he show was causing the wine to turn sour?

• 3. What is the germ theory of disease?• 4. What did Pasteur’s swan neck

experiments disprove?

Robert Koch• Koch was a country doctor from East Prussia

(now Germany) who was concerned with anthrax which infected cattle and sheep

• In a lab in his home, he injected mice with the blood of diseased cattle, then performed autopsies on the dead mice

• Next he isolated a few bacteria from a mouse’s blood and placed it in the sterile aqueous humor from an ox’s eye

Robert Koch• He watched as the bacteria multiplied

and then turned into resistant spores• Next he took several of the spores and

injected them into healthy mice• The symptoms of anthrax appeared

within hours• Koch autopsied the mice and found their

blood swarming with bacteria

Robert Koch

Robert Koch’s Postulates

Solid Culture Media• Koch developed a solid culture media on

which bacteria would grow by solidifying beef broth and gelatin

• When inoculated onto the surface, bacteria grew vigorously and produced discrete visible, colonies

• Now agar is used instead of gelatin because it can resist digestion by certain bacteria and it remains solid when incubated at high temperatures

End of the Golden Age

• The Golden Age witnessed a series of discoveries unparalleled in the identification of the agents of disease

• Scientists developed an awareness that infectious disease was caused by microorganisms and that the chains of transmission could be broken

• These discoveries led to calls for sterile practices in hospitals, pasteurization of milk, purification of water, control of insects and care in the preparation of foods

• This led to a substantial reduction in the incidence of bacterial diseases – but viruses were still to come!

Compound Light Microscope

Light Path

Light Path

Oil Immersion

Wheat Rust• A disease of wheat caused by a fungus of the

genus Puccinia• Infections can lead up to 20% yield loss -

exacerbated by dying leaves which fertilize the fungus

• Small brown pustules develop on the leaf blades in a random scatter distribution. They may group into patches in serious cases. Infectious spores are transmitted via the soil.