---
title: "Bacteriophages as Predators and as Laboratory Tools"
description: "Phages shape bacterial populations in the wild and were the system in which much of molecular genetics was first worked out. Their specificity for a host strain is what makes them useful for typing ba"
canonical: https://lightmysky.com/learn/science/bacteriophages-as-predators-and-as-laboratory-tools-mt_vOnjSpXjrj
source: https://lightmysky.com/learn/science/bacteriophages-as-predators-and-as-laboratory-tools-mt_vOnjSpXjrj.md
retrieved: 2026-09-12
---

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# Bacteriophages as Predators and as Laboratory Tools

Phages shape bacterial populations in the wild and were the system in which much of molecular genetics was first worked out. Their specificity for a host strain is what makes them useful for typing bacteria and for delivering genes.

Subject: Science · Area: Microbiology · Ages 19 to 21
Page: https://lightmysky.com/learn/science/bacteriophages-as-predators-and-as-laboratory-tools-mt_vOnjSpXjrj

## Ready when they can

- Explains what host range means and what determines it.
- Reads a plaque assay as a count of infectious particles.
- Gives one use of phages that depends on their narrow specificity.

## Lesson: Hunters that read surfaces

Picture a hunter built for exactly one job: finding its bacterium. Tail fibres read the cell surface the way your hand reads a glove, and only a matching spot lets it dock and inject its genome. One hunter may strike a single strain and ignore everything else nearby. That narrow menu is on purpose.

**Example.** Now turn that precision into a counting tool yourself. Spread hunters on a lawn of bacteria and each starter particle carves one clear dead zone, so counting zones counts viruses in the sample. One zone, one starter: the math is that clean. Measuring becomes seeing.

The same strictness solved old mysteries and still types germs today. Drip a panel of known hunters on an unknown culture and the one that bursts it names the strain. Early geneticists went further: marked coats stayed outside while marked genes entered cells, proving DNA is the hereditary stuff. Hunters also deliver genes.

**Tip.** Finally, watch hunters prune nature like predators. They kill the strain that grows common enough to meet its hunter, then fade back. Change the surface spot and docking fails, which is one clean route to resistance. Range, counting, typing, and resistance all flow from matching.

**Recap.** You match tails to spots to explain range, counts, typing, and resistance.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Viral Life Cycles: Lysis, Lysogeny and Latency](https://lightmysky.com/learn/science/viral-life-cycles-lysis-lysogeny-and-latency-mt_OI8-dySb5A)

## Opens up

- [Horizontal Gene Transfer: Uptake, Contact and Delivery](https://lightmysky.com/learn/science/horizontal-gene-transfer-uptake-contact-and-delivery-mt_mrmn0_nQf7)