Mathematical modelling of CRISPR-Cas system effects on biofilm formation

• Main Authors: Qasim Ali, Lindi M. Wahl
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2017-08-01
• Series: Journal of Biological Dynamics
• Subjects: Bacteria; bacteriophage; biofilm; CRISPR-Cas system; lysogens
• Online Access: http://dx.doi.org/10.1080/17513758.2017.1314025

Clustered regularly interspaced short palindromic repeats (CRISPR), linked with CRISPR associated (Cas) genes, can confer adaptive immunity to bacteria, against bacteriophage infections. Thus from a therapeutic standpoint, CRISPR immunity increases biofilm resistance to phage therapy. Recently, however, CRISPR-Cas genes have been implicated in reducing biofilm formation in lysogenized cells. Thus CRISPR immunity can have complex effects on phage–host–lysogen interactions, particularly in a biofilm. In this contribution, we develop and analyse a series of dynamical systems to elucidate and disentangle these interactions. Two competition models are used to study the effects of lysogens (first model) and CRISPR-immune bacteria (second model) in the biofilm. In the third model, the effect of delivering lysogens to a CRISPR-immune biofilm is investigated. Using standard analyses of equilibria, stability and bifurcations, our models predict that lysogens may be able to displace CRISPR-immune bacteria in a biofilm, and thus suggest strategies to eliminate phage-resistant biofilms.