The AHL- and BDSF-Dependent Quorum Sensing Systems Control Specific and Overlapping Sets of Genes in Burkholderia cenocepacia H111

Nadine Schmid,Ulrich Omasits,Leo Eberl,Yinyue Deng,Lian-Hui Zhang,Alexander Grunau,Christian H Ahrens,Claudio Aguilar,Gabriella Pessi,Aurelien L Carlier,Willem Van Schaik

doi:10.1371/journal.pone.0049966

Abstract

Quorum sensing in Burkholderia cenocepacia H111 involves two signalling systems that depend on different signal molecules, namely N-acyl homoserine lactones (AHLs) and the diffusible signal factor cis-2-dodecenoic acid (BDSF). Previous studies have shown that AHLs and BDSF control similar phenotypic traits, including biofilm formation, proteolytic activity and pathogenicity. In this study we mapped the BDSF stimulon by RNA-Seq and shotgun proteomics analysis. We demonstrate that a set of the identified BDSF-regulated genes or proteins are also controlled by AHLs, suggesting that the two regulons partially overlap. The detailed analysis of two mutually regulated operons, one encoding three lectins and the other one encoding the large surface protein BapA and its type I secretion machinery, revealed that both AHLs and BDSF are required for full expression, suggesting that the two signalling systems operate in parallel. In accordance with this, we show that both AHLs and BDSF are required for biofilm formation and protease production.

Highlights

Many bacteria are capable of coordinating gene expression in a cell density-dependent manner, a phenomenon commonly referred to as quorum sensing (QS) [1]
Our combined RNA-Seq and proteome analysis revealed that the set of genes regulated by BDSF in B. cenocepacia H111 shows a substantial overlap with the set of genes recently shown to be CepR-regulated (Figure S1)
The gene aidA, which encodes a protein required for killing of the nematode Caenorhabditis elegans [22], is stringently regulated by C8-HSL (.100-fold at the transcript level, Table 3, Figure 2C and D) whereas the effect of BDSF is marginal (4-fold to 6-fold at the transcript level, Tables 2 and 3, Figure 2C and D)

Summary

Introduction

Many bacteria are capable of coordinating gene expression in a cell density-dependent manner, a phenomenon commonly referred to as quorum sensing (QS) [1]. QS systems rely on the production and release of small signal molecules into the environment. Bacteria respond to these signals when their concentration has reached a certain threshold (and the bacterial population has attained a critical density), upon which expression of target genes is activated or repressed. The CepR regulons of two B. cenocepacia, K56-2 and H111, have previously been determined using functional genomics approaches [8,10,11] These investigations identified many genes encoding virulence factors [12] but has shown that in strain H111 AHLdependent expression of a large surface protein (bapA, BCAM2143) is critical for biofilm formation on abiotic surfaces [11]

Methods

Results

Conclusion