The biofilm matrix scaffold of Pseudomonas aeruginosa contains G-quadruplex extracellular DNA structures.

Content Provider	Europe PMC
Author	Seviour, Thomas Winnerdy, Fernaldo Richtia Wong, Lan Li Shi, Xiangyan Mugunthan, Sudarsan Foo, Yong Hwee Castaing, Remi Adav, Sunil S. Subramoni, Sujatha Kohli, Gurjeet Singh Shewan, Heather M. Stokes, Jason R. Rice, Scott A. Phan, Anh Tuân Kjelleberg, Staffan
Abstract	Extracellular DNA, or eDNA, is recognised as a critical biofilm component; however, it is not understood how it forms networked matrix structures. Here, we isolate eDNA from static-culture Pseudomonas aeruginosa biofilms using ionic liquids to preserve its biophysical signatures of fluid viscoelasticity and the temperature dependency of DNA transitions. We describe a loss of eDNA network structure as resulting from a change in nucleic acid conformation, and propose that its ability to form viscoelastic structures is key to its role in building biofilm matrices. Solid-state analysis of isolated eDNA, as a proxy for eDNA structure in biofilms, reveals non-canonical Hoogsteen base pairs, triads or tetrads involving thymine or uracil, and guanine, suggesting that the eDNA forms G-quadruplex structures. These are less abundant in chromosomal DNA and disappear when eDNA undergoes conformation transition. We verify the occurrence of G-quadruplex structures in the extracellular matrix of intact static and flow-cell biofilms of P. aeruginosa, as displayed by the matrix to G-quadruplex-specific antibody binding, and validate the loss of G-quadruplex structures in vivo to occur coincident with the disappearance of eDNA fibres. Given their stability, understanding how extracellular G-quadruplex structures form will elucidate how P. aeruginosa eDNA builds viscoelastic networks, which are a foundational biofilm property.
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Journal	NPJ Biofilms and Microbiomes [NPJ Biofilms Microbiomes]
Volume Number	7
DOI	10.1038/s41522-021-00197-5
PubMed Central reference number	PMC7979868
Issue Number	1
PubMed reference number	33741996
e-ISSN	20555008
Language	English
Publisher	Nature Publishing Group UK
Publisher Date	2021-03-19
Publisher Place	London
Access Restriction	Open
Rights License	Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. © The Author(s) 2021
Subject Keyword	Biofilms Pathogens
Content Type	Text
Resource Type	Article
Subject	Biotechnology Microbiology Applied Microbiology and Biotechnology