Gene expression in Pseudomonas aeruginosa biofilms : evidence for biofilm specific regulation and iron override effects on quorum sensing
Year: 2001
Type: dissertation
Abstract: Prior studies established that the Pseudomonas aeruginosa oxidative stress response is influenced by iron availability, whereas more recent evidence demonstrated that it was also controlled by quorum sensing (QS) regulatory circuitry.In the present study, sodA (encoding manganese-cofactored superoxide dismutase, Mn-SOD) and Mn-SOD were used as a reporter gene and endogenous reporter enzyme, respectively, to reexamine control mechanisms that govern the oxidative stress response, and to better understand how QS and a nutrient stress response interact or overlap in this bacterium.In cells grown in trypticase soy broth (TSB), Mn-SOD was expressed in wild-type stationary phase planktonic cells, but not in a Iasl or IasR mutant.However, Mn-SOD activity was completely suppressed in the wild-type strain when the TSB medium was supplemented with iron.Reporter gene studies indicated that sodA transcription could be variably induced in iron-starved cells of all three strains, depending on growth stage.Iron starvation induction of sodA was greatest in the wild-type strain and least in the IasR mutant, and was maximal in stationary phase cells.Reporter experiments in the wild-type strain showed increased lasI::lacZ transcription in response to iron limitation, whereas the expression level in the las mutants was minimal and iron starvation induction of lasI::lacZ did not occur.Studies comparing sodA expression in P. aeruginosa biofilms and planktonic cultures were also initiated.In wild-type biofilms, Mn-SOD was not detected until after 6 d, although it could be rapidly detected in iron-limited biofilms.Unlike planktonic bacteria, Mn-SOD was constitutive in the lasI and IasR mutant biofilms, but could be suppressed if the growth medium was amended with 25 |iM ferric chloride.This study demonstrated that: i) the nutritional status of the cell GENE EXPRESSION IN PSEUDOMONAS AERUGINOSA BIOFILMS: EVIDENCE
Author: Nikki Bollinger
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W321446065