A c-di-GMP-Modulating Protein Regulates Swimming Motility of Burkholderia cenocepacia in Response to Arginine and Glutamate

Brijesh Kumar,Silvia T Cardona,John L Sorensen

doi:10.3389/fcimb.2018.00056

Brijesh Kumar, Silvia T Cardona + Show 1 more

Open Access

https://doi.org/10.3389/fcimb.2018.00056

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Abstract

Burkholderia cenocepacia is an opportunistic bacterium that can thrive in different environments, including the amino acid-rich mucus of the cystic fibrosis (CF) lung. B. cenocepacia responds to the nutritional conditions that mimic the CF sputum by increasing flagellin expression and swimming motility. Individual amino acids also induce swimming but not flagellin expression. Here, we show that modulation of the second messenger cyclic dimeric guanosine monophosphate (c-di-GMP) levels by the PAS-containing c-di-GMP phosphodiesterase, BCAL1069 (CdpA), regulates the swimming motility of B. cenocepacia K56-2 in response to CF sputum nutritional conditions. Heterologous expression of WspR, a diguanylate cyclase, in B. cenocepacia K56-2 caused an increase in c-di-GMP levels and reduced swimming motility but did not affect flagellin expression or flagellar biosynthesis. After insertional mutagenesis of 12 putative genes encoding c-di-GMP metabolizing enzymes, one mutant of the locus BCAL1069 (cdpA), exhibited decreased swimming motility independent of flagellin expression in CF sputum nutritional conditions and an increase in intracellular c-di-GMP levels. The reduced swimming motility phenotype of the BCAL1069 mutant was observed in the presence of arginine and glutamate, but not of histidine, phenylalanine, or proline. The B. cenocepacia CdpA was also found to be involved in regulation of protease activity but not in biofilm formation. Altogether, these results highlight a role of B. cenocepacia BCAL1069 (CdpA) in sensing the nutritional conditions of the CF sputum and eliciting a pathogenic response that includes swimming motility toward amino acids and an increase in protease activity.

Highlights

Cyclic-dimeric-guanosine monophosphate or c-di-GMP is an intracellular second messenger present in a wide range of bacterial species (Camilli and Bassler, 2006)
We showed that the cystic fibrosis (CF) sputum nutritional conditions increased the swimming motility of B. cenocepacia K56-2 through upregulated flagellin expression and a change in the flagellation pattern (Kumar and Cardona, 2016)
To address whether c-di-GMP regulates the swimming motility of B. cenocepacia, we cloned the wspR gene from P. aeruginosa PAO1 and overexpressed it in B. cenocepacia K56-2 (WT)

Summary

Introduction

Cyclic-dimeric-guanosine monophosphate or c-di-GMP is an intracellular second messenger present in a wide range of bacterial species (Camilli and Bassler, 2006). The sensory domains recognize small molecules and subsequently activate the receiver domain, resulting in functional changes in bacterial physiology and virulence factors, including motility (Galperin et al, 2001; Römling et al, 2013). In Salmonella Typhimurium, the amino acid arginine was demonstrated to modulate c-di-GMP levels through a Cache-GGDEF domaincontaining protein, leading to cellulose secretion and biofilm formation (Mills et al, 2015). These findings suggest that pathogenic bacteria can respond to environmental/nutritional cues and regulate virulence factors by modulating c-di-GMP levels through signal transduction pathways

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