Epigenetic Influence of Dam Methylation on Gene Expression and Attachment in Uropathogenic Escherichia coli

Abstract

Urinary tract infections (UTI) are among the most frequently encountered infections in clinical practice globally. Predominantly a burden among female adults and infants, UTIs primarily caused by uropathogenic Escherichia coli (UPEC) results in high morbidity and fiscal health strains. During pathogenesis, colonization of the urinary tract via fimbrial adhesion to mucosal cells is the most critical point in infection and has been linked to DNA methylation. Furthermore, with continuous exposure to antibiotics as the standard therapeutic strategy, UPEC has evolved to become highly adaptable in circumventing the effect of antimicrobial agents and host defenses. Hence, the need for alternative treatment strategies arises. Since differential DNA methylation is observed as a critical precursor to virulence in various pathogenic bacteria, this body of work sought to assess the influence of the DNA adenine methylase (dam) gene on gene expression and cellular adhesion in UPEC and its potential as a therapeutic target. To monitor the influence of dam on attachment and FQ resistance, selected UPEC dam mutants created via one-step allelic exchange were transformed with cloned qnrA and dam complement plasmid for comparative analysis of growth rate, antimicrobial susceptibility, biofilm formation, gene expression, and mammalian cell attachment. The absence of DNA methylation among dam mutants was apparent. Varying deficiencies in cell growth, antimicrobial resistance and biofilm formation, alongside low-level increases in gene expression (recA and papI), and adherence to HEK-293 and HTB-9 mammalian cells were also detected as a factor of SOS induction to result in increased mutability. Phenotypic characteristics of parental strains were restored in dam complement strains. Dam’s vital role in DNA methylation and gene expression in local UPEC isolates was confirmed. Similarly to dam-deficient Enterohemorrhagic E. coli (EHEC), these findings suggest unsuccessful therapeutic use of Dam inhibitors against UPEC or dam-deficient UPEC strains as attenuated live vaccines. However, further investigations are necessary to determine the post-transcriptional influence of dam on the regulatory network of virulence genes central to pathogenesis.

The impact of DNA adenine methyltransferase knockout on the development of triclosan resistance and antibiotic cross-resistance in Escherichia coli

“…Here we have shown that the loss of dam results in a significantly decreased mean generation time and that its absence contributes to differences in the ABR profile compared to a wild-type parental strain and confers a measure of resistance to the antimicrobial TCS. The increased generation time (Table 2) seen with the dam knockout matches observations of damdeficient strains of uropathogenic E. coli [34]. This increase is likely a consequence of the role of dam in replication [32,34].…”

Drivers and sites of diversity in the DNA adenine methylomes of 93 Mycobacterium tuberculosis complex clinical isolates

“…In other bacteria, hypomethylation has been attributed to transcription factors occluding MTase access to DNA when their respective target motifs overlap (Beaulaurier et al; Hernday et al, 2002 ; Stephenson and Brown, 2016 ). To determine if this may be the case in M. tuberculosis , we scanned the context sequence of each consistently hypomethylated site for TFBS motifs previously characterized in M. tuberculosis ( Minch et al, 2015 ).…”

“…In M. tuberculosis , MamA-mediated transcriptional regulation has been demonstrated at four promoters in M. tuberculosis ( Shell et al, 2013 ), presumably through interaction with the −10 promoter element. A second characterized mechanism of DNA methylation mediated cis-regulation is interaction between methylated bases, MTases, and transcription factors ( Beaulaurier et al, 2015 ; Hernday et al, 2002 ; Stephenson and Brown, 2016 ), which has been hypothesized to occur at specific sites in M. tuberculosis ( Phelan et al, 2018 ; Zhu et al, 2016 ).…”

Global Screening of Salmonella enterica Serovar Typhimurium Genes for Desiccation Survival

“…Dam, DNA adenine methylase, plays important role in DNA replication, DNA mismatch repair and SOS response (a genome-wide response to DNA damage where cell cycle is arrested and DNA repair and mutagenesis is active; Stephenson and Brown, 2016 ). Dam plays a protective role during oxidative stress in S .…”