History of Microbes (#1)

Antoni van Leeuwenhoek

late 1600s - was not a scientist to start off

• made the first simple microscope by making his own glass lens

  • observed animacules… looked at pond samples and saw protozoa that moved so he named them

  • first visualization of living microorganisms

Louis Pasteur

late 1800s - set out to disprove spontaneous generation (the belief that living things could come from nonliving matter)

• designed the swan neck flask experiment

swan neck flask experiment

designed by Louis Pasteur

• boil broth within the flask to kill any organisms

• leave neck open/bent to allow for gas exchange but prevent introduction of dust/microbes

• flasks sit open for 18 months under a staircase, no contamination after this

  • breaking neck caused contamination from the air

  • tilting the flasks also caused dust to contaminate the broth (proved microbes come from dust, not just spontaneously)

boiled infusion, infusion sits and no microbes appear, 18 months makes infusion remain sterile indefinitely (proves nothing comes from nothing)

Robert Koch

late 1800s - first discovered/studied anthrax in animals

• found the same rod shaped bacteria in every animal that was diseased

• established germ theory of disease (not set in stone but can be applied in situations where a microorganism connects to a disease); used a combo of swan neck experiment and anthrax research

Koch’s postulates

criteria used to demonstrate a certain microorganism causes a certain disease; does not work for every pathogen; first used with anthrax because it’s easily isolated/found

1. organism should be present in animals with disease but absent in healthy (ex: if you don’t have anthrax, you shouldn’t see the bacteria)

2. organism must be cultivated in a pure culture away from the animal’s body (the disease is able to be grown apart from the individual)

3. culture should be able to initiate characteristic disease symptoms when transferred to a susceptible animal (can be transported and cause the same issues)

4. the organism must be reisolated from the newly infected animal and shown to be the same as the original (can be grown in different places and stay the same)

problems with Koch’s postulates

• carriers can harbor/transmit infection without having disease symptoms (ex: being covid asymptomatic)

• normal flora - microbes naturally present can cause illness despite being normal (ex: e. coli. in our system can be good but e. coli in an undercooked burger is bad)

• some organisms cannot be grown in a culture

• immunity blocks reinfection; if immune to a pathogen, disease cannot be caused in a susceptible animal

Redi

late 1600s; decaying meat experiments… sealed meat had no gas exchange but unsealed did… Pasteur took this and made it better

• early challenge to spontaneous generation

Neddham

1700s

similar to Pasteur, did not effectively boil to kill all organisms so failed… seemed to support spontaneous generation due to error

Spallanzi

1700s

contradicted Needham, similar to Pasteur when he sealed flasks and found no contamination

Buchner

1800s

contributed to understanding/discovering enzymes

Gram

1800s

developed the Gram stain technique (technique to see things under a microscope)

Semmelweis

1800s

found that handwashing dramatically decreased mortality in labor and delivery after students came straight from cadaver lab

Lister

1800s

antisepsis, put sterilization on tools so the wounds wouldn’t get bacteria

Nightingale

1800s

introduced standards of eating, showering, and washing clothes in Civil War patientsS

Snow

1800s

father of epidemiology, mapped the outbreak of cholera and figured out it was the contaminated water pump

Jenner

1700s/1800s

vaccines, found that a small exposure protects you from a big exposure (used cow pox to protect from small pox)

Ehrlich

1800s"

“magic bullet” - arsenic based pills to kill of infection but too much could kill you

prions

misfolded proteins that cause other proteins to misfold

• infectious

virus

obligate intracellular parasite

• infectious microorganism that cannot reproduce or survive outside a living host cell

helminths

eukaryotic work that lives inside of an organism to feed on its nutrients and cause disease

bacteria

prokaryotic with free flowing genetic material