Role of multicellular aggregates in biofilm formation

Kragh, Kasper; Hutchison, Jaime B.; Melaugh, Gavin; Rodesney, Chris; Roberts, Aled; Irie, Yasuhiko; Jensen, Peter �.; Diggle, Stephen P.; Allen, Rosalind J.; Gordon, Vernita; Bjarnsholt, Thomas

Abstract

In traditional models of in vitro biofilm development, individual bacterial cells seed a surface, multiply, and mature into multicellular, three-dimensional structures. Much research has been devoted to elucidating the mechanisms governing the initial attachment of single cells to surfaces. However, in natural environments and during infection, bacterial cells tend to clump as multicellular aggregates, and biofilms can also slough off aggregates as a part of the dispersal process. This makes it likely that biofilms are often seeded by aggregates and single cells, yet how these aggregates impact biofilm initiation and development is not known. Here we use a combination of experimental and computational approaches to determine the relative fitness of single cells and preformed aggregates during early development of Pseudomonas aeruginosa biofilms. We find that the relative fitness of aggregates depends markedly on the density of surrounding single cells, i.e., the level of competition for growth resources. When competition between aggregates and single cells is low, an aggregate has a growth disadvantage because the aggregate interior has poor access to growth resources. However, if competition is high, aggregates exhibit higher fitness, because extending vertically above the surface gives cells at the top of aggregates better access to growth resources. Other advantages of seeding by aggregates, such as earlier switching to a biofilm-like phenotype and enhanced resilience toward antibiotics and immune response, may add to this ecological benefit. Our findings suggest that current models of biofilm formation should be reconsidered to incorporate the role of aggregates in biofilm initiation.

Citation

Kragh, K., Hutchison, J. B., Melaugh, G., Rodesney, C., Roberts, A., Irie, Y., …Bjarnsholt, T. (2016). Role of multicellular aggregates in biofilm formation. mBio, 7(2), Article e00237-16. https://doi.org/10.1128/mBio.00237-16

• Journal Article Type: Article
• Acceptance Date: Feb 22, 2016
• Publication Date: Mar 22, 2016
• Deposit Date: Aug 23, 2016
• Publicly Available Date: Aug 23, 2016
• Journal: mBio
• Print ISSN: 2161-2129
• Electronic ISSN: 2150-7511
• Publisher: American Society for Microbiology
• Peer Reviewed: Peer Reviewed
• Volume: 7
• Issue: 2
• Article Number: e00237-16
• DOI: https://doi.org/10.1128/mBio.00237-16
• Public URL: https://nottingham-repository.worktribe.com/output/779659
• Publisher URL: http://mbio.asm.org/content/7/2/e00237-16
• Contract Date: Aug 23, 2016