SiaA and SiaD are essential for inducing autoaggregation as a specific response to detergent stress in Pseudomonas aeruginosa

Authors

  • Janosch Klebensberger,

    1. Universität Konstanz, Fachbereich Biologie, Mikrobielle Ökologie, Fach M654, 78457 Konstanz, Germany.
    2. Centre for Marine Bio-Innovation, School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia.
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  • Antoinette Birkenmaier,

    1. Universität Konstanz, Fachbereich Biologie, Mikrobielle Ökologie, Fach M654, 78457 Konstanz, Germany.
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  • Robert Geffers,

    1. Array Facility/Cell Biology, HCI – Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany.
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  • Staffan Kjelleberg,

    1. Centre for Marine Bio-Innovation, School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia.
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  • Bodo Philipp

    Corresponding author
    1. Universität Konstanz, Fachbereich Biologie, Mikrobielle Ökologie, Fach M654, 78457 Konstanz, Germany.
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*E-mail bodo.philipp@uni-konstanz.de; Tel. (+49) 7531 884541; Fax (+49) 7531 884047.

Summary

Cell aggregation is a stress response and serves as a survival strategy for Pseudomonas aeruginosa strain PAO1 during growth with the toxic detergent Na-dodecylsulfate (SDS). This process involves the psl operon and is linked to c-di-GMP signalling. The induction of cell aggregation in response to SDS was studied. Transposon and site-directed mutagenesis revealed that the cupA-operon and the co-transcribed genes siaA (PA0172) and siaD (PA0169) were essential for SDS-induced aggregation. While siaA encodes a putative membrane protein with a HAMP and a PP2C-like phosphatase domain, siaD encodes a putative diguanylate cyclase involved in the biosynthesis of c-di-GMP. Complementation studies uncovered that the loss of SDS-induced aggregation in the formerly isolated spontaneous mutant strain N was caused by a non-functional siaA allele. DNA-microarray analysis of SDS-grown cells revealed consistent activation of eight genes, including cupA1, with known or presumptive important functions in cell aggregation in the parent strain compared with non-aggregating siaA and siaD mutants. A siaAD-dependent increase of cupA1 mRNA levels in SDS-grown cells was also shown by Northern blots. These results clearly demonstrate that SiaAD are essential for inducing cell aggregation as a specific response to SDS and suggest that they are responsible for perceiving and transducing SDS-related stress.

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