Physiology of Quorum Sensing Signal Degradation by Soil and Clinical Pseudomonas sp. Isolates

EPA Grant Number: U916203
Title: Physiology of Quorum Sensing Signal Degradation by Soil and Clinical Pseudomonas sp. Isolates
Investigators: Huang, Jean J.
Institution: California Institute of Technology
EPA Project Officer: Zambrana, Jose
Project Period: January 1, 2003 through January 1, 2006
Project Amount: $108,344
RFA: STAR Graduate Fellowships (2003) Recipients Lists
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Microbiology


Quorum sensing (QS), or cell-density dependent communication by bacteria via small diffusible molecules, mediates a variety of microbial behaviors in nature from bioluminescence to antibiotics production to biofilm formation and cell motility. Pseudomonas sp. microbes are diverse and ubiquitous in the environment. Several members of this group are known to form symbiotic or pathogenic relationships with plants and animals. These interactions are controlled by the microbe's QS, which is known to be mediated by acyl homoserine lactone (AHSL) molecules. AHSL signals represent a wide class of molecules used by Gram-negative bacteria in QS. The objective of this research project is to characterize the physiology and significance of AHSL quorum signal degradation by soil and clinical isolates.


Experiments have found that two closely related pseudomonads—a species isolated from the soil and a clinical isolate—can degrade AHSLs. We have found that there are differences in regulation in their ability to degrade AHSL signals, and these differences could be because of the different roles for this activity in each species. For the soil isolate, I hope to understand how the ability to degrade signals might affect a microbial community where some bacteria use QS to establish a niche, and others may use this degradation process to thwart their QS neighbors, and to determine if signal degradation could be involved in the natural regulation of pseudomonad QS.

Supplemental Keywords:

fellowship, quorum sensing, QS, signal degradation, acyl homoserine lactone, AHSL, microbial community, Gram-negative bacteria.

Progress and Final Reports:

  • 2003
  • 2004
  • Final