N-acyl homoserine lactone mediated interspecies interactions between <i>A. baumannii</i> and <i>P. aeruginosa</i>

<div><p> <i>Acinetobacter baumannii</i> and <i>Pseudomonas aeruginosa</i> are pathogens capable of colonizing the same infection sites and employing N-acyl homoserine lactone (AHL) based quorum-sensing systems to co-ordinate biofilm formation. Hence, the effect of <i>P. aeruginosa</i> AHLs on biofilm formation by <i>A. baumannii</i> and <i>vice versa</i> were investigated using the biofilm impaired quorum sensing mutants, <i>A. baumannii</i> M2 (<i>aba</i>I::Km) and <i>P. aeruginosa</i> PAO-JP2. Complementing the mutants with heterologous, extracted and pure AHLs increased biofilm mass significantly. The surface area coverage and biovolume also increased significantly as observed by confocal scanning laser microscopy which corroborated scanning electron microscope analysis. Autoinducer synthase gene promoters of <i>A. baumannii</i>, P_<i>aba</i>I-<i>lac</i>Z, and <i>P. aeruginosa</i>, P_<i>las</i>I-<i>lacZ</i>, were induced (<i>p</i> < 0.05) by heterologous AHLs. Growth of <i>A. baumannii</i> was not inhibited by pyocyanin of <i>P. aeruginosa</i> which may allow their co-existence and interaction in the clinical setting, thereby affecting the severity of combined infections and therapeutic measures to control them.</p> </div

Additional file 14: of Quorum sensing in thermophiles: prevalence of autoinducer-2 system

STRING analysis of LuxS protein of Geobacillus thermoglucosidasius. (PDF 225 kb

Ellagic Acid Derivatives from <em>Terminalia chebula</em> Retz. Downregulate the Expression of Quorum Sensing Genes to Attenuate <em>Pseudomonas aeruginosa</em> PAO1 Virulence

<div><h3>Background</h3><p>Burgeoning antibiotic resistance in <em>Pseudomonas aeruginosa</em> has necessitated the development of anti pathogenic agents that can quench acylhomoserine lactone (AHL) mediated QS with least risk of resistance. This study explores the anti quorum sensing potential of <em>T. chebula</em> Retz. and identification of probable compounds(s) showing anti QS activity and the mechanism of attenuation of <em>P. aeruginosa</em> PAO1 virulence factors.</p> <h3>Methods and Results</h3><p>Methanol extract of <em>T. chebula</em> Retz. fruit showed anti QS activity using <em>Agrobacterium tumefaciens</em> A136. Bioactive fraction (F7), obtained by fractionation of methanol extract using Sephadex LH20, showed significant reduction (p<0.001) in QS regulated production of extracellular virulence factors in <em>P. aeruginosa</em> PAO1. Biofilm formation and alginate were significantly (p<0.05) reduced with enhanced (20%) susceptibility to tobramycin. Real Time PCR of F7 treated <em>P. aeruginosa</em> showed down regulation of autoinducer synthase (<em>lasI</em> and <em>rhlI</em>) and their cognate receptor (<em>lasR</em> and <em>rhlR</em>) genes by 89, 90, 90 and 93%, respectively. Electrospray Ionization Mass Spectrometry also showed 90 and 64% reduction in the production of 3-oxo-C₁₂HSL and C₄HSL after treatment. Decrease in AHLs as one of the mechanisms of quorum quenching by F7 was supported by the reversal of inhibited swarming motility in F7-treated <em>P. aeruginosa</em> PAO1 on addition of C₄HSL. F7 also showed antagonistic activity against 3-oxo-C₁₂HSL-dependent QS in <em>E. coli</em> bioreporter. <em>C. elegans</em> fed on F7-treated <em>P. aeruginosa</em> showed enhanced survival with LT50 increasing from 24 to 72 h. LC-ESI-MS of F7 revealed the presence of ellagic acid derivatives responsible for anti QS activity in <em>T. chebula</em> extract.</p> <h3>Conclusions</h3><p>This is the first report on anti QS activity of <em>T. chebula</em> fruit linked to EADs which down regulate the expression of <em>lasIR</em> and <em>rhlIR</em> genes with concomitant decrease in AHLs in <em>P. aeruginosa</em> PAO1 causing attenuation of its virulence factors and enhanced sensitivity of its biofilm towards tobramycin.</p> </div

Additional file 9: of Quorum sensing in thermophiles: prevalence of autoinducer-2 system

Multiple sequence alignment of SAH hydrolase from thermophilic and mesophilic eubacteria by MultAlin. High conservation among SAH hydrolases has been observed. (PDF 274 kb

Additional file 15 of Quorum sensing in thermophiles: prevalence of autoinducer-2 system

STRING analysis of LuxS protein of Caminibacter mediatlanticus. (PDF 90 kb

Additional file 6: of Quorum sensing in thermophiles: prevalence of autoinducer-2 system

Multiple sequence alignment of LuxS protein from mesophilic and thermophilic eubacteria by MultAlin. Invariant residues are highlighted in red colour. The conserved HTLEH motif and other conserved residues are highlighted within boxes. (PDF 111 kb

Additional file 3: of Quorum sensing in thermophiles: prevalence of autoinducer-2 system

Multiple sequence alignment of AgrA protein from Staphylococcus aureus and thermophilic eubacteria by MultAlin. (PDF 40 kb

Relative expression of <i>lasIR</i> and <i>rhlIR</i> genes of <i>P. aeruginosa</i> PAO1 in the presence of 0.5 mg/ml F7 as determined by qRT PCR.

<p>Relative expression of <i>lasIR</i> and <i>rhlIR</i> genes of <i>P. aeruginosa</i> PAO1 in the presence of 0.5 mg/ml F7 as determined by qRT PCR.</p

Additional file 1: of Quorum sensing in thermophiles: prevalence of autoinducer-2 system

Peptide based quorum sensing systems. (PDF 10 kb

Additional file 8: of Quorum sensing in thermophiles: prevalence of autoinducer-2 system

Multiple sequence alignment of MTA/SAH nucleosidase from thermophilic eubacteria by MultAlin. There is no conservation among Pfs protein sequences. (PDF 138 kb