Abstract
Biofilms of the Gram-negative bacterium Pseudomonas aeruginosa are one of the
major causes of complicated urinary tract infections with detrimental outcome. To
develop novel therapeutic strategies the molecular adaption strategies of P.
aeruginosa biofilms to the conditions of the urinary tract were investigated
thoroughly at the systems level using transcriptome, proteome, metabolome and
enzyme activity analyses. For this purpose biofilms were grown anaerobically in
artificial urine medium (AUM). Obtained data were integrated bioinformatically
into gene regulatory and metabolic networks. The dominating response at the
transcriptome and proteome level was the adaptation to iron limitation via the
broad Fur regulon including 19 sigma factors and up to 80 regulated target genes
or operons. In agreement, reduction of the iron cofactor-dependent nitrate
respiratory metabolism was detected. An adaptation of the central metabolism to
lactate, citrate and amino acid as carbon sources with the induction of the
glyoxylate bypass was observed, while other components of AUM like urea and
creatinine were not used. Amino acid utilization pathways were found induced,
while fatty acid biosynthesis was reduced. The high amounts of phosphate found in
AUM explain the reduction of phosphate assimilation systems. Increased quorum
sensing activity with the parallel reduction of chemotaxis and flagellum assembly
underscored the importance of the biofilm life style. However, reduced formation
of the extracellular polysaccharide alginate, typical for P. aeruginosa biofilms
in lungs, indicated a different biofilm type for urinary tract infections.
Furthermore, the obtained quorum sensing response results in an increased
production of virulence factors like the extracellular lipase LipA and protease
LasB and AprA explaining the harmful cause of these infections.
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