Biological sciences

The birth of Microbiology

Microbiology Crash Course, History of Science #24: What makes beer? Single-celled organisms. What makes us cough and feel like sleeping for twelve straight hours Straight? Single-celled organisms; AKA microbes, germs, the tiny machines that allow us to digest—and can kill us.

“What is life?” It turns out, life is relentless, everywhere on earth! Microbes are invisible. they’re single cells. So to understand microbes—that is, to do microbiology—scientists first needed to study cells.

Brief history of microbiology:

German botanist Matthias Schleiden and physiologist Theodor Schwann proposed a modern cell theory around 1837: every living thing is made up of one or more cells. So the cell was the fundamental unit of life, the thing that gives structure to all forms of life. Amazingly, Schleiden—who studied plants—and Schwann—who studied animals—both noticed tiny dots in the middles of the cells they looked at under their microscopes.

These nuclei must somehow be important to all life, they figured—correctly. Darwin’s chief public defender, Thomas Henry Huxley, also wrote a article called “The Cell–Theory” in 1853. Where the Germans were cataloging different microscopic forms, Huxley proposed a mechanistic model: cells are little factories with different parts that have different functions. Their functions make the parts add up into an organic whole. Not every scientist believed cell theory right away, but many came around, as microscope-enabled evidence mounted. And yet, being able to observe single-celled organisms didn’t immediately lead scientists to connect them to disease. In fact, medicine in the early 1800s mostly worked the way it had hundreds or even a thousand years earlier. It was still all about liquids called humors. But some diseases were understood differently. These were caused by a kind of invisible badness in the environment called a miasma.

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According to miasma theory, diseases were caused by foul-smelling airs that came from rotting meats, swamps, and other putrefying sources. Before you knock it, think about it: this theory mostly works. Dangerous microbes grow on smelly, dirty stuff. The smell is a byproduct of the microbes’ eating organic matter. But even today, we can’t see these microbes without instruments. So following our unaided senses is still smart: don’t eat gross trash! Sniff the turkey before you eat it. And then, just eat it anyway like I did this morning. By the mid-1800s, however, a few scientific rebels were pushing a germ theory of disease. This holds that germs, or pathogenic microorganisms, cause infectious diseases. Around this time, a nasty germ called Vibrio cholerae provided an opportunity to test the theory out.h Cholera had ravaged England since the germ started to travel widely out of south Asia in the early 1800s, hitching rides on the expanding armada of merchant ships.

Empire had all kinds of unpredicted downsides. In 1854, a bad cholera epidemic hit Broad Street in the Soho neighborhood of London, killing over six hundred people. One doctor named John Snow had a hunch about what was going on. Snow created a map of the outbreak and noted that the cases seemed to cluster around one public well. He hypothesized that cholera microbes were rapidly multiplying in its water. So he convinced the Soho council to remove the well’s pump handle. People went elsewhere for water, and the cholera infections decreased. John Snow became a hero! Saving Lives! Even though, it turned out, the outbreak was already in decline when he removed the handle. Thus proving that some John Snows, do know somethings. Snow’s quick thinking didn’t really prove germ theory. For germs to replace miasmas in their minds, scientists would require a better model of what germs are, and how they behave. For that, we turn to one of the first experimental microbiologists and a dude whose name you probably should know from milk labels: Louis Pasteur Born in France in 1822—the same year as Galton—Pasteur was a chemist, not a physician. But he is known for his work on germs and health. Pasteur is credited as the co-founder of microbiology and the founder of modern zymology, the science of fermentation.

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Fermentation is the biological and chemical process needed to make beer, wine, yogurt, cheese, bread, and many other foods. Thought Bubble, show us what that means. Chemically, fermentation is the conversion of sugar molecules into ethanol, or alcohol, and carbon dioxide. In food, this usually happens thanks to bacteria or yeast. Looking good, Saccharomyces! Pasteur first connected yeast to the fermentation of wine in 1857. He observed that microscopic yeast on grape skins makes grape juice ferment into wine. If you sterilize the skins, killing the yeast, fermentation won’t happen. Pasteur even made the the analogy that the microbes growing in wine and beer were similar to the microbes causing diseases in humans and animals.

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