Quorum Regulation over Long Distances

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Material Information

Title:
Quorum Regulation over Long Distances Sinorhizobium meliloti Surfing Motility and Gene Regulation by Diffusing Autoinducer Signals
Physical Description:
1 online resource (110 p.)
Language:
english
Creator:
Dilanji, Gabriel E
Publisher:
University of Florida
Place of Publication:
Gainesville, Fla.
Publication Date:

Thesis/Dissertation Information

Degree:
Doctorate ( Ph.D.)
Degree Grantor:
University of Florida
Degree Disciplines:
Physics
Committee Chair:
HAGEN,STEPHEN JAMES
Committee Co-Chair:
MEISEL,MARK W
Committee Members:
TEPLITSKI,MAXIM
STANTON,CHRISTOPHER JAY
MCKINLEY,SCOTT

Subjects

Subjects / Keywords:
autoinducer -- bacteria -- biomaterials -- biophysics -- motility -- quorum -- sinorhizobia
Physics -- Dissertations, Academic -- UF
Genre:
Physics thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract:
The role of diffusion and entropic forces in signaling and motility are investigated for the quorum sensing (QS) bacterium Sinorhizobium meliloti. Experiments and numerical modeling probed the spatial and temporal patterns of gene expression that develop in response to diffusing autoinducer signals. The studies and results presented herein are significant because QS is central to the regulation of numerous microbial behaviors including biofilm formation, symbiosis, motility, and virulence. QS is a mechanism for bacterial communication based on the exchange of diffusible small molecule signals known as autoinducers, which accumulate in the environment as the population density grows. Once the autoinducer concentration reaches a threshold, it triggers population-wide changes in gene expression. S. meliloti, a soil dwelling bacterium that enters into a nitrogen-fixing symbiosis with plants of the genus Medicago, was chosen for this work for two main reasons. Firstly, the QS system of S. meliloti employs several N-acyl-L-homoserine lactone (AHL) autoinducers that differ in the length (C8-C18) and structure (e.g. keto-substituted) of their carbon side chains. Experiments using fluorescent protein reporters for QS activation show that the diffusing signal readily activates a QS circuit at a range ~1 cm, on time scales ~10 h. On the other hand, long-chain AHLs, which have poor solubility and diffusive mobility, activate gene expression in a spatially extended colony over time scales of ~20 h and over distances of ~2mm (C16:1-HSL) or ~6mm (3OC14-HSL and 3OC16:1-HSL). Moreover the patterns of activation are qualitatively unlike simple solutions to the diffusion equation, as the response time is surprisingly insensitive to the distance from the signal source. These results show that diffusion of an autoinducer signal can be effective in synchronizing gene expression on macroscopic distances. Secondly, S. meliloti on a soft agar surface exhibits a unique spreading behavior that is characterized by expansion of a mucoid layer accompanied by complex pattern formation. Experimental data and modeling show that both the spreading and pattern formation are driven by two entropic phenomena induced by the secreted exopolysaccharide EPSII, namely the osmotic extraction of water from the agar and the crowding or depletion attraction between the cells.
General Note:
In the series University of Florida Digital Collections.
General Note:
Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility:
by Gabriel E Dilanji.
Thesis:
Thesis (Ph.D.)--University of Florida, 2014.
Local:
Adviser: HAGEN,STEPHEN JAMES.
Local:
Co-adviser: MEISEL,MARK W.
Electronic Access:
RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2014-11-30

Record Information

Source Institution:
UFRGP
Rights Management:
Applicable rights reserved.
Classification:
lcc - LD1780 2014
System ID:
UFE0046534:00001