Most of us consider microorganisms to be invisible yet pervasive buggers that cause gum disease if we don’t brush our teeth, food poisoning in under-cooked food, and unanimously agree that they need to be destroyed. We buy products claiming to kill 99.9% of them from our homes and surfaces and try to push the worry about that 0.1% out of our minds. Maybe we even have a notion of “good” vs. “bad” bacteria. We are afraid of these organisms and are constantly at war.

But should we fear them or praise them? Given the global pandemonium over the COVID-19 outbreak (viral, not bacterial), the invisible world of microorganisms has grabbed our full attention.

By nonchalantly consuming and administering antibiotics we have grossly underestimated the efficiency and intelligence of these molecular sacs of lipid. Bacteria are the oldest kingdom of organisms on Earth — billions of years of evolution and adaptation have made them the most resilient species alive.

Our survival on this planet is utterly dependent on them. They generate the building blocks of life, colonize every living structure, and are indispensable to all ecosystems.

I know they say it’s turtles all the way down, but in actual fact it’s bacteria.

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Thriving in adverse conditions

Bacteria love adverse conditions. They evolved during volatile climates on Earth 4 billion years ago when the atmosphere consisted of nitrogen, argon, neon, carbon dioxide and water vapour.

📄 Coral reef bleaching

Scientists stationed on an East Antarctic ice sheet drilled into Lake Vostok, sealed under ice for 420,000 years. DNA analysis revealed bacteria closely related to species alive today in extreme environments such as the Mariana Trench.

📄 Microbial life in Lake Vostok
📄 Geomicrobiology of Subglacial Ice Above Lake Vostok

We also know bacteria exist in volcanoes, sulfur lakes, and ocean trenches. These extremophiles inhabit every improbable corner of the planet. If a mass extinction happens, bacteria will survive and evolve into unimaginable forms.

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Thrifty bacteria

The earliest bacteria invented fermentation as a source of energy, converting sugar to ATP. Fermentation is inefficient — alcohol and acids are excreted — but other bacteria evolved to feed on these wastes. These food chains still exist today in low-oxygen, low-light places like our guts.

📄 Bacterial enzyme which breaks down plastic

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Nitrogen fixation

One of the earliest bacterial lineages, Clostridia, acquired the ability to extract nitrogen gas from the atmosphere and incorporate it into amino acids, nucleotides and other compounds.

Industrial nitrogen fixation requires 300 atmospheres and 500 °C. No plant or animal can do it — only certain bacteria.

Without nitrogen-fixing bacteria, life would starve. Thankfully, Clostridia, Azotobacter, Rhizobia and friends supply the biosphere with vital nitrogen.

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Bacteria are the Earth’s undertakers

Bacterial teams maintain Earth’s equilibrium. They recycle once-living matter into food and energy.

Lynn Margulis:
Bacteria purify the Earth’s water and make soil fertile. They perpetuate the chemical anomaly that is our atmosphere, constantly producing fresh supplies of reactive gases.

Atmospheric chemist James Lovelock suggested:

• Methane regulates oxygen and ventilation
• Ammonia sets alkalinity of lakes/oceans
• Carbon dioxide modulates planetary temperature
• Methyl chloride regulates ozone

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Bacterial reproduction and gene transfer

Bacteria reproduce asexually by simple division — one daughter every 20 minutes. After 2 days, 2^144 individuals could form; after 4 days, more than protons in the universe.

They also have “sex”: exchanging genes via conjugation, even with dead cells. A bacterium can carry 90% new genes without reproducing.

Replicons (packets of DNA/RNA) can also move between cells in a process called transduction.

Lynn Margulis:
People and other eukaryotes are like solids frozen in a mold, whereas bacteria are like a liquid or gas — genes in constant flux.

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Bacteria work in teams

Bacteria never act alone. They cooperate in teams (biofilms), recycle each other’s byproducts, and stabilize ecosystems.

They also partner with fungi, plants, and animals. For example, lichens are coalitions of cyanobacteria and fungi functioning as one.

📄 Biofilms

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Bacteria vs. Virus

Viruses hijack our cells, but for bacteria, viral encounters can be opportunities. They deploy Cas9 to cut viral RNA, then integrate snippets into their genome as defense.

This ancient system is the foundation of modern CRISPR gene editing.

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Drug resistance

Bacteria share drug resistance genes via conjugation and transduction.

For every million divisions, one mutation occurs. Most are harmful, but occasionally a mutation confers resistance — which can then spread rapidly.

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Bacteria are the default OS

If Earth is hardware, bacteria are the default operating system. They:

• Maintain the atmosphere
• Recycle nutrients
• Fix nitrogen

If Earth “reboots,” bacteria restart the system from scratch.

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Sources

📖 Microcosmos: Four Billion Years of Microbial Evolution — Lynn Margulis & Dorion Sagan