Differential gene expression of P. aeruginosa in a rhizosphere biofilm on poplar tree
roots was examined in order to identify new virulence factors from this human pathogen.
Changes in gene expression for poplar trees contacted with P. aeruginosa was examined as well
to identify the response of poplar roots to P. aeruginosa infection. This is the first study of the
whole-transcriptome analysis of P. aeruginosa on a plant tree root. The 20 most highly-induced
genes of P. aeruginosa were examined for their role in biofilm formation, rhizosphere
colonization, barley germination, and poplar tree killing assays. Seven previously
uncharacterized virulence genes (PA1385, PA2146, PA2462, PA2463, PA2663, PA4150, and
PA4295) were identified.
The role of PA2663, a hypothetical protein discovered in the microarrays of P.
aeruginosa while killing poplar trees, was examined in further detail. Expression of PA2663
protein increases biofilm formation in P. aeruginosa PAO1 drastically. By complementing the
PA2663 mutation in trans and by studying with DNA microarrays and RT-PCR the PA2663
mutant vs. the wild-type strain, PA2663 was confirmed to be related to biofilm formation and
was found that it is the first protein to control the psl operon in P. aeruginosa PAO1.
Furthermore, PA2663 protein increases pyoverdine synthesis and quorum sensing (QS)-
regulated phenotypes. A biofilm formation-related hypothetical protein, PA0939, was identified in this study.
The effects of indole and 7-hydroxyindole on P. aeruginosa virulence factors were also
examined for the first time. Indole and 7HI repressed expression of mexGHI-opmD multidrug
efflux pump genes and genes involved in synthesis of QS-regulated virulence factors
(pyocyanin, rhamnolipid, PQS, and pyoverdine production).
In addition, the effects of an anti-cancer uracil analog, 5-fluorouracil (5-FU) on P.
aeruginosa virulence factors and E. coli K-12 biofilm formation were examined. 5-FU repressed
biofilm formation, abolished quorum-sensing phenotypes, and reduced virulence in P.
aeruginosa. DNA microarray and biofilm studies with 5-FU in E. coli revealed that 5-FU
controls biofilm formation through the AriR protein in E. coli K-12 strain. The effects of lsrR
and lsrK mutations on E. coli biofilm formation were also examined by flow cell experiments.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2326 |
| Date | 15 May 2009 |
| Creators | Attila, Can |
| Contributors | Wood, Thomas K. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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