The virulence factor regulator and quorum sensing regulate the type I-F CRISPR-Cas mediated horizontal gene transfer in Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa is capable of thriving in diverse environments due to its network of regulatory components for effective response to stress factors. The survival of the bacteria is also dependent on the ability to discriminate between the acquisition of beneficial and non-beneficial genetic materials via horizontal gene transfer (HGT). Thus, bacteria have evolved the CRISPR-Cas adaptive immune system for defense against the deleterious effect of phage infection and HGT. By using the transposon mutagenesis approach, we identified the virulence factor regulator (Vfr) as a key regulator of the type I-F CRISPR-Cas system in P. aeruginosa. We showed that Vfr influences the expression of the CRISPR-Cas system through two signaling pathways in response to changes in calcium levels. Under calcium-rich conditions, Vfr indirectly regulates the CRISPR-Cas system via modulation of the AHL-QS gene expression, which could be vital for defense against phage infection at high cell density. When encountering calcium deficiency, however, Vfr can directly regulate the CRISPR-Cas system via a cAMP-dependent pathway. Furthermore, we provide evidence that mutation of vfr reduces the CRISPR-Cas spacer acquisition and interference of HGT. The results from this study add to the regulatory network of factors controlling the CRISPR-Cas system in response to abiotic factors in the environment. The findings may facilitate the design of effective and reliable phage therapies against P. aeruginosa infections, as targeting Vfr could prevent the development of the CRISPR-Cas mediated phage resistance.

Structural and functional diversity of bacterial cyclic nucleotide perception by CRP proteins

“…Instead, Vfr regulates virulence-related features such as expression of Type IV pili-, Type III and Type II secretion system-, quorum-sensing system-, and exolysin-encoding genes, thereby promoting a planktonic lifestyle and acute invasive infection as opposed to a sessile lifestyle and persistent infection (reviewed in Coggan and Wolfgang 2012 , Berry et al 2018 ). Furthermore, other important traits such as CRISPR–CAS-related genes are regulated by Vfr (Dela Ahator et al 2022 ). In total, the Vfr regulon comprises over 200 genes (Suh et al 2002 , Wolfgang et al 2003 ).…”

Comparative Analysis of CRISPR-Cas Systems in Pseudomonas Genomes

“…So far, numerous studies have been conducted describing the CRISPR-Cas systems in P. aeruginosa, both at the structural and functional levels [16][17][18][19][20][21][22][23], but not throughout the entire Pseudomonas genus. The search for CRISPR structures in the genomes of the Pseudomonas genus is significant as it contributes to the study of the diversity and distribution of these genetic elements in various environments.…”