What is Microbiology?•The science of microorganisms (verysmall, unicellular organisms)•The discipline is just over a century old•Has given rise to molecular biologyand biotechnology
3 historical discoveries•Invention of the microscope•Disproving spontaneous generation•Demonstrating microorganisms causedisease
Antony van Leeuwenhoek (1632-1723)• Inventor of the first microscope
• Leeuwenhoek earned his living as a draper, but spent much ofhis spare time constructing simple microscopes composed ofdouble convex glass lenses held between two silver plates (figurebelow)• his microscope could magnify around 50 to 300 times,
SPONTANEOUS GENERATION•Redi demonstrated that organisms did not arise fromnonliving material.•FRANCESCO REDI devised a set of experiments todemonstrate that if pieces of meat were covered withgauze so that flies could not reach them, no “worms”appeared in the meat, no matter how rotten it was.However, no maggots were observed in sealed piece ofmeat (figure below)
• Despite the proof that maggots did not arise spontaneously,some scientist still believed in spontaneous generation.
• Pasteur demonstrated that microorganisms inthe air were responsible for food spoilage Constructed a swan-necked flask
• Pasteur’s experiment for the competition involved his famous“swannecked” flasks
He boiled infusion in flask, heated the glass necks, and drewthem out into long, curved tubes open at the end. Air could enterthe flask without being subjected to any of the treatments thatcritics had claimed destroyed its effectiveness.Airborne microorganisms could also enter the necks of the flask,but they became trapped in the curves of the neck and neverreached the infusions. The infusions from Pasteurs experimentremained sterile unless a flask was tipped so that the infusionflowed into the neck and then back into the flask.This manipulation allowed microorganisms trapped in the neckto wash into the infusion, where they could grow and cause theinfusion to become cloudy.
In another experiment Pasteur filtered air through three cottonplugs. he then immersed the plugs in sterileinfusions, demonstrating that growth occurred in the infusionsfrom organisms trapped in the plugs. Pasteur, with his swan-necked flask, and Tyndall, with his dust-free air, finally dispelled the idea of spontaneous generation.
Germ Theory of DiseaseKOCH’S CONTRIBUTIONS Koch developed four postulates that aided in the definitiveestablishment of the germ theory of disease. Koch’s Postulatesare follows:
• The cell was discovered by Robert Hooke in 1665. Heexamined (under a coarse, compound microscope) verythin slices of cork and saw a multitude of tiny pores thathe remarked looked like the walled compartments amonk would live in. Because of this association, Hookecalled them cells, the name they still bear. • Drawing of the structure of cork by Robert Hooke that appeared in Micrographic.