Microbiome in cystic fibrosis: shaping polymicrobial interactions for advances in antibiotic therapy

Recent molecular methodologies have demonstrated a complex microbial ecosystem in cystic fibrosis (CF) airways, with a wide array of uncommon microorganisms co-existing with the traditional pathogens. Although there are lines of evidence supporting the contribution of some of those emergent species for lung disease chronicity, clinical significance remains uncertain for most cases. A possible contribution for disease is likely to be related with the dynamic interactions established between microorganisms within the microbial community and with the host. If this is the case, management of CF will only be successful upon suitable and exhaustive modulation of such mixed ecological processes, which will also be useful to predict the effects of new therapeutic interventions.The authors report no declarations of interest. The authors acknowledge the financial support provided by the Portuguese Foundation for Science and Technology (grant: SFRH/BD/47613/2008 - Susana Lopes, ANTIPEP project PTDC/SAU-SAP/113196/2009 and DNA mimics project PIC/IC/82815/2007). The authors would also like to acknowledge the support of the COST-Action TD1004: Theragnostics for imaging and therapy

Structure and regulation of EAL domain proteins

The formation and dispersal of bacterial biofilms is strongly correlated with cellular levels of bis-(3′–5′) cyclic dimeric guanosine monophosphate, cyclic di-GMP, a secondary messenger that has been shown to be involved in regulation of a broad range of cellular processes in bacteria. Diguanylate cyclases (DGCs) are required for synthesis of cyclic di-GMP, with phosphodiesterases (PDEs) responsible for its breakdown. This review focuses on PDEs characterised by the presence of the conserved “EAL” sequence motif. Typically found in multi-domain proteins, EAL domains can couple to sensory or regulatory domains that allow their activity to be regulated by environmental stimuli or cellular cues. Additionally, catalytically inactive EAL PDEs are suggested to have a sensory or otherwise regulatory function. Recent structure determination provides a wealth of information on PDE function and regulation and has provided novel insight into the enzymatic reaction mechanism. Several regulatory layers may control activity, including dimerisation, active site formation, and metal coordination. In this review, we provide a concise summary of these exciting findings and highlight open research questions that will allow us in future to decipher many of the cellular signals responsible for regulation of PDE activity and cellular processes influenced by these pivotal enzymes