Morphometric Analysis

Use the free program ImageJ to measure phage characteristics. You can either use it online in a web browser, or download the app to a PC.

 

Setting the Image Scale

Setting the scale in ImageJ
Setting the scale in ImageJ
    • Open the image
    • Go to the Analyze tab and select Set Scale
        • Distance in pixels = 1
        • Unit of length = nm
        • Input pixel size into Known distance
            • You can find this value in the .txt metadata file included with your images
            • Or look for the image magnification at the bottom left (circled in red) and use the corresponding pixel values:
                • x50.0k Pixel Size=0.2380
                • x60.0k  Pixel Size=0.1983
                • x80.0k Pixel Size=0.1488

Measuring features 

  • To measure capsid width, select the Straight Line tool. Click once to specify the beginning point of your line and then drag the mouse to the end point, and release.
  • Go to the Analyze tab and select Measure.
  • The Results window will open. Scroll to the right to find the Length value.
Measuring capsid width
Measuring capsid width using the straight line tool
  • Use the Segmented Line tool to measure curved tails more accurately.
Measuring tail length
Measuring tail length with the segmented line tool