History of microbiology

Cell theory

The principle that cells are the fundamental component of life, and that all cells give rise to other cells.

Simple microscope

A microscope in which light passes through a single lens.

Compound microscope

A microscope in which light passes through two sets of lenses.

Spontaneous generation

The theory that living organisms can arise spontaneously from nonliving matter.

Biogenesis

The principle that living matter is generated only from other pre-existing living matter.

Symbiotic relationship

A close, long-term relationship between two different organisms, forming the conceptual basis of endosymbiotic theory.

Chemotherapy

The treatment of disease by using chemical substances.

Antibiotic

A chemical produced naturally by bacteria or fungi that acts against other microorganisms.

Synthetic drugs

Chemotherapeutic agents prepared from chemical sources in a laboratory.

Pathogen

A disease-causing microorganism.

Pure culture

A population of cells or multicellular organisms growing in the complete absence of other species or microbial types.

Isolate

The separation of a specific microbial strain from a natural, mixed population of living microbes.

Normal microbiota

The population of microorganisms living in and on a host animal or environment that normally cause no harm.

Ignaz Semmelweis

Early proponent of handwashing to prevent the transfer of disease between patients by physicians.

Joseph Lister

Developed procedures for surgical wound care and equipment sterilization, contributing to the germ theory of disease.

Robert Koch

Proved specific microbes cause specific diseases (anthrax, TB) and created Koch's postulates.

Robert Hooke

Observed cork under a compound microscope in 1665 and coined the term 'cells' in Micrographia.

Antonie van Leeuwenhoek

First to observe living microorganisms ('animalcules') using single-lens microscopes; known as the father of microbiology.

Rudolf Virchow

Popularized the concept that all cells arise from pre-existing cells (omnis cellula e cellula) in 1858.

Francesco Redi

Challenged spontaneous generation in 1668 by showing maggots only appeared on meat exposed to flies.

Swan-neck flask experiment

Louis Pasteur's 1859 design showing broth stays sterile when protected from airborne microbes in a curved neck, disproving spontaneous generation.

Major contributions of Louis Pasteur

Disproved spontaneous generation, showed microbes cause fermentation/spoilage, created pasteurization, and developed rabies and anthrax vaccines.

Endosymbiotic theory

Theory stating that mitochondria and chloroplasts were once free-living prokaryotes engulfed by a host cell, popularized by Lynn Margulis.

Evidence for endosymbiotic theory

Organelles contain circular DNA and $70\text{S}$ ribosomes, divide by binary fission, possess double membranes, and match bacterial size.

Origin of mitochondria vs. chloroplasts

Mitochondria evolved from engulfed aerobic bacteria, whereas chloroplasts evolved from engulfed cyanobacteria.

Germ theory of disease

The scientific concept stating that many diseases are caused by specific microorganisms rather than miasma (bad air).

Koch's postulates memory hook

Find it, grow it, give it, find it again.

Limitations of Koch's postulates

Inability to culture some pathogens, existence of healthy carriers, ethical restrictions on human infection, and diseases caused by multiple microbes.

Molecular Koch's postulates

Stanley Falkow's 1988 adaptation focusing on identifying specific virulence genes rather than whole organisms.

Selective toxicity

The property of an antimicrobial drug that harms a pathogen without significantly harming the host.

Paul Ehrlich

Pioneered the concept of selective toxicity ('magic bullet') and discovered Salvarsan (compound 606) for syphilis.

Alexander Fleming

Discovered penicillin in 1928 after observing that Penicillium mold inhibited Staphylococcus growth.

Koch's postulate 1

The suspected pathogen must be found in every case of the disease and not in healthy individuals.

Koch's postulate 2

The pathogen must be isolated from the sick host and grown in pure culture.

Koch's postulate 3

The pure culture must cause the same disease when introduced into a healthy, susceptible host.

Koch's postulate 4

The same pathogen must be re-isolated from the newly infected host.