Local Excitation, Global Inhibition Mechanism for Gradient Sensing: An Interactive Applet

(LEGI Model of Chemotaxis Applet)

Brett Kutscher1, Peter Devreotes2, andPablo A. Iglesias1*

1Department of Electrical and Computer Engineering, Johns Hopkins University, 3400 North Charles Street, 226 Barton Hall, Baltimore, MD 21218, USA.

2Department of Cell Biology, Johns Hopkins University School of Medicine, 725 North Wolfe Street, 114 WBSB, Baltimore, MD 21205, USA.

*Corresponding author. Telephone, +1-410-516-6026; fax, +1-410-516-5566; E-mail: pi{at}

Applet. LEGI model of chemotaxis. In the local excitation, global inhibition (LEGI) model, temporal and spatial sensing involve two opposing processes representing local excitation (E) and global inhibition (I). Receptor occupancy controls the steady-state activity of the two processes, and the balance between the two regulates the activity of the response regulator (RR). The applet allows the user to set various parameters to explore how altering these parameters changes the cell's responses to homogeneous chemoattractant, a single source of chemoattractant, or two sources of chemoattractant. The applet is available from the link below "Access Applet" or from

[Access Applet]

Technical Details

Format: Java applet

Requirements: This applet will run with a Java-enabled browser (obtain the latest Java plug-in from


Citation: B. Kutscher, P. Devreotes, P. A. Iglesias, Local excitation, global inhibition mechanism for gradient sensing: An interactive applet. Sci. STKE2004, pl3 (2004).

© 2004 American Association for the Advancement of Science