Robert Koch • Pure Culture Studio

Streaking for Isolation: Virtual Agar Plate Simulation

Practice a simple 4-quadrant streak on a teal-themed virtual agar plate. Drag the loop to spread bacteria and then "incubate" to see isolated colonies. Designed for undergraduate microbiology labs.

Teal-themed and minimal

Just follow the steps shown: flame → load → streak 1→2→3→4 → incubate.

Dense growth (heavy streak)

Thinning growth

Isolated colonies

Loop streak path

Drag to streak • Then incubate

Status: Step 1: Flame the loop

Simple sequence: (1) Click "Flame loop" to sterilize it. (2) Click "Touch mixed culture" to load many cells. (3) Drag in Quadrant 1 (top-right) for a thick streak. (4) Without reloading, drag into Quadrants 2 → 3 → 4 so the streak gets lighter. (5) Click "Incubate plate" to see where isolated colonies appear.

The goal is to turn a very crowded starting streak into a gentle gradient, ending with single, well-separated colonies in the last quadrant. Each isolated colony represents a pure culture from one starting cell.

Learning goals

Use a sterile loop (aseptic technique).
Understand the 4-quadrant streak: each new quadrant = fewer cells.
See how dilution by streaking creates isolated colonies.
Connect isolated colonies to pure cultures used in Koch-style experiments.

How this simulation works

1) Flame = clean loop (no extra microbes). 2) Touch mixed culture = loop has many starting cells. 3) Streak Quadrant 1 = heavy growth zone (too crowded to see singles). 4) Drag into Quadrants 2, 3, and 4 without reloading = each pass carries fewer cells (dilution). 5) Incubate = early quadrants look like lawns; edges of later quadrants show single teal dots. Each dot represents a colony from one original cell: a pure culture.

Suggested activities

Do an orderly 1→2→3→4 streak and incubate. Find where single colonies appear.
Reset and scribble heavily in all quadrants. Incubate and compare: almost no isolated colonies.
Ask which areas you would pick from to start a pure culture and why.

Focus on the idea: each step should reduce cell numbers on the loop, not draw artistic patterns.