Secretins of type-two secretion systems are necessary for exopolymeric slime secretion in cyanobacteria and myxobacteria

Abstract

Cyanobacteria and myxobacteria display gliding motility associated with the secretion of an exopolymeric slime through nozzle-like structures. Here, we use biochemical and structural assays to show that these nozzles are composed of secretins of the PilQ/GspD family, which are known to form outer membrane gates in type-two secretion systems (T2SSs) and other bacterial protein secretion systems. We show that gspD is an essential gene in Myxococcus xanthus, and its downregulation by conditional knockdown renders this bacterium defective in both slime secretion and gliding motility. In cyanobacteria, available data suggest that the exopolymeric slime is a polysaccharide, although the precise nature of the slime in myxobacteria remains unclear. Our results, therefore, indicate that secretins may be required for the secretion of non-proteinaceous polymers in certain bacteria.

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Item Type:	Article
Authors/Creators:	Zuckerman, D.M. https://orcid.org/0000-0002-2261-1633 So, J.M.T. https://orcid.org/0009-0008-1807-2033 Hoiczyk, E. https://orcid.org/0000-0001-6613-3955
Copyright, Publisher and Additional Information:	© The Author(s) 2025. Open Access: This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, 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 licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence 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 licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Keywords:	Bacterial secretion; Bacterial structural biology; Biofilms; Cellular microbiology
Dates:	Accepted: 18 August 2025 Published (online): 26 September 2025 Published: 26 September 2025
Institution:	The University of Sheffield
Academic Units:	The University of Sheffield > Faculty of Science (Sheffield) > School of Biosciences (Sheffield)
Date Deposited:	29 Sep 2025 14:42
Last Modified:	29 Sep 2025 14:42
Status:	Published
Publisher:	Springer Science and Business Media LLC
Refereed:	Yes
Identification Number:	10.1038/s41467-025-63426-x
Open Archives Initiative ID (OAI ID):	oai:eprints.whiterose.ac.uk:232336

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Secretins of type-two secretion systems are necessary for exopolymeric slime secretion in cyanobacteria and myxobacteria

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