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

Abstract

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.

Self-produced exopolysaccharide is a signal that stimulates biofilm formation inPseudomonas aeruginosa

“…We initially targeted our analysis to three diguanylate cyclases that have been strongly linked to P. aeruginosa biofilm formation: SadC, SiaD, and WspR (15,16,28). Using directed mutagenesis, we demonstrated that SadC and SiaD both contribute to Pslinduced c-di-GMP production (Fig.…”

“…The SiaABCD proteins form a transmembrane signal transduction complex that responds to SDS to activate c-di-GMP synthesis by SiaD (16). It is possible that Psl acts by inducing transcription of the sadC and/or siaD genes.…”

“…However, few specific instances of environmental signals that modulate the activity of these enzymes have been identified. In P. aeruginosa, the diguanylate cyclases SiaD and WspR are activated upon exposure to SDS or contact with solid surfaces, respectively (15)(16)(17). In Escherichia coli, the activity of the DosCP cyclase/phosphodiesterase pair is modulated by oxygen availability (18), whereas diffusible signal factor was shown to activate c-di-GMP phosphodiesterase activity through the two-component regulatory system RpfG/C in Xanthomonas campestris (19).…”

Modification of Glycan Expression in Staphylococcus epidermidis to Prevent Biofilm Formation

“…It occurs in response to adverse environmental condition or stress and involves multiple regulatory signals that reprogramme gene expression (Monds and O'Toole 2009). This gene expression reprogramming alters the expression of virulence factors, nutrient utilisation, surface molecules and equips the bacteria with the arsenals which enable their survival in adverse environmental conditions (Klebensberger et al, 2009). Ðapa et al (2013) showed that lower concentrations of antibiotics can cause stress in bacteria thereby inducing biofilm formation.…”

The anti-cancerous drug doxorubicin decreases the c-di-GMP content in Pseudomonas aeruginosa but promotes biofilm formation

“…The organization, composition and dynamic of the biofilm community confer to the cells protection against threats from the environment, such as natural predators or exposure to harmful substances (Chiang et al, 2012;Klebensberger et al, 2009;Malone et al, 2010;Mishra et al, 2012;Tseng et al, 2013). While this mode of life appears to be beneficial for the bacterial community, it is the cause of persistent infections in medical settings and fouling problems in various industrial settings (Ciofu et al, 2015;Costerton et al, 1999;Dosler & Karaaslan, 2014;Flemming, 2002;Hill et al, 2005).…”