Formation and Dispersion : a Pseudomonas Aeruginosa Review

Since its initial discovery as an allosteric factor regulating cellulose biosynthesis in Gluconacetobacter xylinus, the list of functional outputs regulated by c-di-GMP has grown. We have focused this article on one of these c-di-GMP-regulated processes, namely, biofilm formation in the organism Pseudomonas aeruginosa. The majority of diguanylate cyclases and phosphodiesterases encoded in the P. aeruginosa genome still remain uncharacterized; thus, there is still a great deal to be learned about the link between c-di-GMP and biofilm formation in this microbe. In particular, while a number of c-di-GMP metabolizing enzymes have been identified that participate in reversible and irreversible attachment and biofilm maturation, there is a still a significant knowledge gap regarding the c-di-GMP output systems in this organism. Even for the well-characterized Pel system, where c-di-GMP-mediated transcriptional regulation is now well documented, how binding of c-di-GMP by PelD stimulates Pel production is not understood in any detail. Similarly, c-di-GMP-mediated control of swimming, swarming and twitching also remains to be elucidated. Thus, despite terrific advances in our understanding of P. aeruginosa biofilm formation and the role of c-di-GMP in this process since the last version of this book (indeed there was no chapter on c-di-GMP! ) there is still much to learn. BIOFILM FORMATION AND OTHER RELEVANT PHENOTYPES IN PSEUDOMONAS AERUGINOSA P. aeruginosa is a Gram-negative bacterium that has become an indispensable model organism in our quest to understand the A-to-Z of bacterial biofilms (1). It is genetically tractable, has a sequenced and annotated genome (http://www.pseudomonas.com), and boasts a number of useful tools (2, 3) that facilitate both in vivo and in vitro studies. Although it is commonly found as an environmental isolate, it is also an opportunistic pathogen capable of colonizing plants and mammalian hosts and is particularly significant for its efficient colonization of the lungs of cystic fibrosis patients (4–6). The versatility of P. aeruginosa is in large part attributed to a battery of traits that provide it with selective advantage(s) across diverse environments. Like many other bacteria, P. aeruginosa is capable of transitioning between motile and sessile/biofilm lifestyles, which is believed to contribute to this bacterium’s versatility. Bacteria were once perceived to be simple, singlecelled organisms; however, it is quite clear that microbes can participate in a broad range of complexmulticellular behaviors, including quorum sensing, the formation of complex spore-forming aggregates by Myxococcus and Received: 12 September 2014, Accepted: 19 November 2014, Published: 3 April 2015 Editors: Mahmoud Ghannoum, Case Western Reserve University, Cleveland, OH; Matthew Parsek, University of Washington, Seattle, WA; Marvin Whiteley, University of Texas at Austin, Austin, TX; and Pranab Mukherjee, Case Western Reserve University, Cleveland, OH Citation: Ha D-G, O’Toole GA. 2015. c-di-GMP and its effects on biofilm formation and dispersion: a pseudomonas aeruginosa review. Microbiol Spectrum 3(2):MB-0003-2014. doi:10.1128 /microbiolspec.MB-0003-2014. Correspondence: G. A. O’Toole, georgeo@dartmouth.edu © 2015 American Society for Microbiology. All rights reserved. ASMscience.org/MicrobiolSpectrum 1 Downloaded from www.asmscience. org by