Germs of Life and Death

"So Very Small

By Thomas Levenson

Random House, 448 pages, $35

On Nov. 4, 1856, Monsieur Bigo of Lille, France, awaited a visit from the local chemistry instructor. Bigo wasn't used to hosting academics. He owned a factory in town that produced great vats of beet juice, which he fermented into alcohol for use in local industries. At least, that was the idea. But for months the batches were turning sour, transforming into a foul-smelling liquid of no use to anyone. With his livelihood at stake, Bigo invited a 33-year-old chemist to take a look. The chemist's name was Louis Pasteur.

Pasteur, who was also a pharmacist and microbiologist, would eventually gain worldwide renown for his contributions to germ theory, the discovery of vaccines and the process that bears his name, pasteurization. But the road to transforming public health would begin in a fermentation vat filled with fetid beet grist and colonies of helpful (and hurtful) microbes. Bigo's invitation wouldn't merely change the manufacturer's fortunes [1]; it would change the world.

In fact, microbes are the world, responsible for much of what goes on in it. As anyone who has attempted a sourdough starter will know, flour mixed with water, when left in the air, will begin to bubble and swell on its own without the need to add yeast. As Thomas Levenson tells us in "So Very Small," fermentation is "one of the first natural processes" that "human societies turned to their own ends." It's the reason why "bread, beer, and wine are as old as civilization."

Under the microscope, Pasteur discovered yeast in the "good" beet alcohol. In the "bad" batches, however, he found a different kind of microbe. Instead of fat yeast globules, there were longer, rod-shaped ones. If Pasteur isolated the yeast and added it to beet juice, he always got an alcohol reaction; if he isolated the other microbe and introduced it into beet juice, the result was a lactic-acid reaction [2]. The other microbes were alive, he concluded, and were eating the sugars and excreting acids and gases. In 1860 Pasteur published a paper, "On the Origin of Ferments," explaining that the tiny organisms were "not a dead substance" but a "germ" of life. And if all germs are life, then life itself is a germ. "Usually," Mr. Levenson writes, "there is no single moment when everything changes." Yet this one paper would put us on a path toward understanding diseases and how to eradicate them.

For too long, humans had believed in something called spontaneous generation, the idea that something could come from nothing -- that eels were born of mud, that maggots were born of rotting meat and that disease was a product of "filth" and even bad smells. We couldn't see the bacteria that produced the stench of rot, nor the tiny fly eggs that had been deposited in food left to lie -- and so, the author reminds us, medical remedies were forever chasing symptoms and not their causes. But the most intriguing point of "So Very Small" isn't that scientific discovery led the way to better treatments. It's that it took so very long to do so.

Mr. Levenson takes the reader on a remarkable journey through history, from the Black Death of the 14th century to the development of germ theory in the 19th and 20th centuries to the continuing battle with Covid-19 in the 21st century. With extraordinary detail and authoritative prose (and not a few very graphic descriptions), the author describes the suffering brought about by ignorance and prejudice.

Lives innumerable were lost to infection as surgeons refused to disinfect their tools.

In the lying-in hospitals of Europe beginning in the 18th century, women died in the thousands from childbed fever because it was easier to believe the fault was in their bodies and not in the doctor's practice. It's chilling to read of physicians claiming that their blood-caked fingernails, spoiled from performing anatomy on rotting corpses, couldn't be to blame for the death of pregnant women -- after all, as one mid-19th-century doctor from Philadelphia insisted, "a gentleman's hands are clean."

Today, Mr. Levenson reminds us, it is no longer common for children to die of measles, diphtheria or whooping cough -- diseases that once killed off a third of children before they reached the age of 5.

We have vaccines that can protect the young and the old alike. We have hospitals free of childbed fever and a host of other plagues that were responsible for mass mortality. But what Mr. Levenson's book makes clear is that the battle against germs never ends. "Almost as soon as it became possible to cure major infectious disease," he tells us, the power to cure "began to erode."

Partly this is due to the evolutionary arms race between humans and bacteria. Antibiotics lose their efficacy as microbes develop new resistance.

More significantly, vaccine-preventable diseases can only be eradicated when the majority, if not the entirety, of a population is innoculated.

We know how to prevent disease, "but the choices individuals and societies have made," Mr. Levenson writes, make it much harder to do so. We may shudder at the Victorian doctor who refuses to take responsibility for a hundred dead mothers, but we should feel the same concern over decisions to cut vital programs that help us track and fight disease. "Wielding our distinct form of technological smarts," Mr. Levenson writes, "without being aware of what the invisible world of life can do makes us more vulnerable, not less." If we want to preserve the victories accumulated over two centuries against the worst killers of the microbe world, we must rebuild public-health systems, monitor disease, protect and fund science, and recognize that we are not the only "actors." We are also acted upon by the tiny creatures all around us.

---

Ms. Schillace, the editor in chief of the journal Medical Humanities, is the host of the online "Peculiar Book Club" podcast and the author of "The Intermediaries," out this month.” [3]

 

[1] To inhibit lactic acid fermentation during alcohol production, several strategies can be employed. These include lowering the temperature, utilizing specific inhibitors, or manipulating the fermentation process itself.

 

Detailed Methods to Inhibit Lactic Acid Fermentation:

 

    1. Lowering Temperature:

    Lactic acid bacteria (LAB) are generally more active at lower temperatures compared to yeasts, which are typically more efficient at higher temperatures. By maintaining a higher temperature during the initial stages of fermentation, you can favor yeast activity and inhibit the growth of LAB.

 

2. Using Inhibitors:

 

    Sulfur Dioxide (SO2): SO2 is a common preservative in winemaking and can effectively inhibit the growth of LAB, especially in acidic environments.

 

Virginiamycin: This antibiotic has been shown to effectively control LAB growth in alcohol fermentation.

Other Chemicals: Chlorine dioxide, 3,4,4'-trichlorocarbanilide (TCC), and potassium sorbate can also be used to inhibit bacterial growth, though they may have potential side effects or be detrimental to yeasts.

 

3. Manipulating the Fermentation Process:

 

    Optimizing Substrate: Ensuring a sufficient concentration of sugar or other readily fermentable carbohydrates can help favor yeast activity and prevent LAB from competing for resources.

 

Fermentation Timing: Allowing yeasts to fully consume sugars before they begin their fermentation cycle can help prevent unwanted side products like lactic acid from being formed.

Extractive Fermentation: This technique can help remove lactic acid as it is produced, thus reducing its inhibitory effects on the fermentation process.

 

4. Temperature Management:

Fermentation can be stopped or slowed by lowering the temperature to below 5°C (41°F), which can deactivate yeasts.

[2] Lactic acid fermentation and alcohol fermentation are two types of anaerobic respiration where pyruvate is processed to regenerate NAD+ from NADH, enabling glycolysis to continue. While both processes start with glycolysis, lactic acid fermentation reduces pyruvate to lactate (lactic acid), while alcohol fermentation converts pyruvate to acetaldehyde, then to ethanol and releases carbon dioxide.

Lactic Acid Fermentation:

 

    Process:

    Lactic acid fermentation occurs in microorganisms like bacteria and in muscle cells during strenuous activity.

 

Product:

The primary product is lactic acid.

Pyruvate Reduction:

In this process, NADH donates electrons to pyruvate, resulting in the formation of lactate and regeneration of NAD+.

Examples:

Lactic acid fermentation is involved in the production of yogurt, sauerkraut, and other fermented foods. It also occurs in muscles during oxygen deficiency, leading to muscle fatigue and soreness.

 

Alcoholic Fermentation:

 

    Process:

    This type of fermentation is primarily carried out by yeast and some bacteria.

 

Product:

The main product is ethanol (a type of alcohol) and carbon dioxide.

Pyruvate Conversion:

 

Pyruvate is first converted to acetaldehyde by removing carbon dioxide. Then, acetaldehyde is reduced to ethanol by NADH, regenerating NAD+.

Examples:

Alcoholic fermentation is crucial for the production of alcoholic beverages and bread.

 

Key Differences:

The primary difference between lactic acid fermentation and alcohol fermentation lies in the final product. Lactic acid fermentation produces lactic acid, while alcohol fermentation produces ethanol and carbon dioxide.

In summary, while both processes are crucial for cellular respiration in anaerobic conditions, they differ in their final products, with lactic acid fermentation producing lactic acid and alcohol fermentation producing ethanol and carbon dioxide.

 

[3] REVIEW --- Books: Germs of Life and Death. Schillace, Brandy.  Wall Street Journal, Eastern edition; New York, N.Y.. 03 May 2025: C9.