Bacteria and viruses are the ultimate invisible world topic. Students can’t see them, so they often default to vague ideas like “germs are bad” or “viruses are basically tiny bacteria.” The fastest way to flip that is to teach microbiology through surprise, scale, and story.

That’s why I love using Strange But True Facts + Two Truths & a Lie as a launchpad. It turns note-taking about microbes into a quick game of scientific detective work where students have to justify their thinking, challenge misconceptions, and build vocabulary in context.

If you want a ready-to-go version built specifically for classrooms, here’s the bacteria/viruses set I use as a staple:

• Bacteria & Viruses | Strange But True Facts + 2 Truths & a Lie Activity Set 

And if you’d rather run this as a mini unit (reading passages + structured tasks + engagement), there’s also a focused bundle:

• Bacteria & Viruses | Biology Focus Unit Bundle (4 resources)

Now, here are six facts that reliably make students go “Wait… WHAT?”—remember, each one is also an easy bridge to curriculum goals in Grades 6–10.

How to use these facts in class (fast, low prep)

Here are three classroom-friendly ways to teach the facts below:

Option A: Bell ringer (5 minutes)

• Put one fact on the board.

• Students write: “Most surprising part” + “One question I have.”

Option B: Two Truths & a Lie (10–15 minutes)

• Give groups 3 statements (2 true, 1 false).

• They must choose the lie and justify why.

Option C: Micro-CER (8 minutes) - Students write a tiny Claim–Evidence–Reasoning response:

• Claim: What does this fact suggest about microbes?

• Evidence: Quote a key number or detail.

• Reasoning: Explain what it means for ecosystems/health/biology.

If you want more microbe-related resources to pair with this (protozoans, bacteria/viruses reading tasks, etc.), the Micro-organisms hub is handy: The Teaching Astrophysicist Micro-organisms resources

The 6 Brilliant Facts

1) There are about 10³¹ viruses on Earth, and many are bacteriophages

That’s a 1 followed by 31 zeros. A huge proportion of Earth’s viruses are bacteriophages (viruses that infect bacteria), making them some of the most abundant biological entities on the planet. (PMC)

Why this matters in science class: This one instantly teaches scale, ecosystems, and the idea that viruses aren’t just “human illness things.” In oceans especially, viruses influence microbial populations and nutrient cycles.

Teach it tomorrow (easy):

• Ask: “If phages infect bacteria, what happens to food webs when bacterial populations change?”

• Extension prompt: “Would fewer viruses always be good?”

2) Some viruses are bigger than some bacteria

“Giant viruses” like Mimivirus blurred the line between what students think viruses “must” be. Some have large particles (big enough to be seen with light microscopy in certain cases) and genomes with hundreds to over a thousand genes reported across giant virus groups. (Nature)

Why this matters in science class: It challenges the oversimplified rule: “Viruses are always tiny and simple.” It also opens a great discussion about how science categories are human-made tools, not perfect boxes.

Teach it tomorrow (easy):

• Put this question on the board: “What makes something ‘alive’?”

• Have students sort features into: “cells,” “viruses,” “both,” “depends.”

3) Some bacteria can breathe metal by exporting electrons

Certain bacteria (including Shewanella and Geobacter) can transfer electrons to materials outside the cell. Research describes conductive “nanowires” and extracellular electron transfer pathways that can link microbial respiration to external surfaces like iron minerals or electrodes. (PNAS)

Why this matters in science class: It connects biology + chemistry + physics in a way students remember. It also introduces real-world applications like bioelectrochemical systems and environmental remediation.

Teach it tomorrow (easy):

• Ask: “If oxygen isn’t available, what else could act as an electron acceptor?”

• Link to redox: oxidation/reduction isn’t just a chemistry chapter—it’s life.

4) Some bacteria can read Earth’s magnetic field like a built-in compass

Magnetotactic bacteria form chains of magnetic crystals (often magnetite) inside the cell. Those magnetosomes help align the bacteria to Earth’s magnetic field, guiding movement in aquatic environments. (Nature)

Why this matters in science class: It’s an unforgettable example of adaptation and cellular structure. It also makes a great bridge to magnetism in physics and Earth science.

Teach it tomorrow (easy):

• Quick model: students draw “magnetosome chain → alignment → movement.”

• Discussion: “What advantage would this give a microbe in muddy water?”

5) Some bacteria run a “light switch” using quorum sensing

The famous squid symbiosis features bacteria (commonly referenced as Vibrio fischeri, also classified as Aliivibrio fischeri) that produce light only when there are enough neighbors.

They use quorum sensing systems to coordinate gene expression and trigger bioluminescence at higher cell densities. (PMC)

Why this matters in science class: Students often picture bacteria as isolated single cells. Quorum sensing shows them bacteria can behave like a coordinated community—amazing for ecology, communication, and gene regulation.

Teach it tomorrow (easy):

• Ask: “Why wait until there are enough bacteria to glow?”

• Connect to: energy cost, survival advantage, symbiosis.

6) You carry about as many bacterial cells as human cells

A widely cited update to the old “10:1” myth suggests the ratio is much closer to about 1:1 (order of magnitude similar), reminding students that microbes are not just invaders - they’re a normal part of human biology. (PubMed)

Why this matters in science class: This is the misconception-buster students need. It supports better thinking about microbiomes, health, antibiotics, and immunity.

Teach it tomorrow (easy):

• Ask: “If microbes are part of us, what does ‘healthy’ mean?”

• Mini debate: Should we aim to kill all bacteria?

Turn these facts into a lesson sequence (one simple plan)

If you want to run a tidy 3-lesson arc:

Lesson 1: Wonder + misconceptions

• Two Truths & a Lie with bacteria/virus statements

• Vocabulary: virus, bacterium, host, phage, microbiome, gene

Lesson 2: Evidence + explanation

• Students pick one fact and write a Micro-CER

• Add a quick data/scale task (orders of magnitude, comparing sizes)

Lesson 3: Application

• Students design a poster or one-slide explanation: “Why microbes matter”

• Or run a short discussion: “Are microbes mostly helpful, harmful, or both?”

To make this plug-and-play (digital + print + presentation), the Strange But True + Two Truths & a Lie set is built for exactly this kind of sequence: Strange but true + 2 truths and a lie Bacteria & Viruses

And if you want more similar classroom-friendly biology sets, you can browse the full category here: Strange but true facts

Final thought: surprise is not fluff, it’s a learning tool

These facts aren’t just fun trivia. Each one is a doorway into big science ideas: scale, evolution, ecosystems, energy transfer, cell structures, and scientific classification. When students are genuinely curious, they ask better questions, use evidence more carefully, and remember what they learn.

That’s the real win.

Thanks for reading

Cheers and stay curious

Oliver - The Teaching astrophysicist