real time imaging of fluorescent flagella- biophysics

Real Time Imaging of Fluorescent Flagellar Filaments

Chiara Decarolis1035375

The Paper

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Objectives

1.Find an innovative way to image E. coli and Salmonella enterica;

2. Study the motility of bacteria: polymorphic transformations on E. Coli related to runs and tumbles.

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Imaging of BacteriaBefore:• Dark field microscopy;• Differential-interference-constrast microscopy.

Drawbacks:• Flare from cell body;• Shallow depth of field.

4Chiara Decarolihttp://commons.wikimedia.org/wiki/File:Dark_Field_Microscope.png

Imaging of Bacteria: a Novel Method

Fluorescent labelling of cells and filaments imaged via a CCD camera mounted on a epiflourescent microscope.

• Different dyes tested: Alexa Fluor 532, 514, 546, 594 and Oregon Green 514;

• Can distinguish cell body and filaments;

• Gives greater detail of motion as highly fluorescent

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Motion of Bacteria

6Real Time Imaging of Fluorescent Flagellar Filaments, Turner et al., Journal Bacteriol, 2000

Runs and Tumbles

• Run: forward steady motion, 1s;• Tumble: erratic motion with little next displacement, 0.1s;

• For a single filament: CCW turning -> run, CW turning -> tumble.

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The Experiment

8Real Time Imaging of Fluorescent Flagellar Filaments, Turner et al., Journal Bacteriol, 2000

Results• Waveforms • Run/Tumble relation:

1. “Not all the motors need to turn CCW for a cell to run, and only a few need to turn CW for it to tumble”.

2. Sequence of waveforms during tumbles: normal, semi-coiled, curly 1.

9Real Time Imaging of Fluorescent Flagellar Filaments, Turner et al., Journal Bacteriol, 2000

Questions?

Chiara Decaroli 10