4-Methylcytosine DNA modification is critical for global epigenetic regulation and virulence in the human pathogenLeptospira interrogans

Abstract

In bacteria, DNA methylation can be facilitated by ‘orphan’ DNA methyltransferases lacking cognate restriction endonucleases, but whether and how these enzymes control key cellular processes are poorly understood. The effects of a specific modification, 4-methylcytosine (4mC), are even less clear, as this epigenetic marker is unique to bacteria and archaea, whereas the bulk of epigenetic research is currently performed on eukaryotes. Here, we characterize a 4mC methyltransferase from the understudied pathogen Leptospira spp. Inactivating this enzyme resulted in complete abrogation of CTAG motif methylation, leading to genome-wide dysregulation of gene expression. Mutants exhibited growth defects, decreased adhesion to host cells, higher susceptibility to LPS-targeting antibiotics, and, importantly, were no longer virulent in an acute infection model. Further investigation resulted in the discovery of at least one gene, that of an ECF sigma factor, whose transcription was altered in the methylase mutant and, subsequently, by mutation of the CTAG motifs in the promoter of the gene. The genes that comprise the regulon of this sigma factor were, accordingly, dysregulated in the methylase mutant and in a strain overexpressing the sigma factor. Our results highlight the importance of 4mC in Leptospira physiology, and suggest the same of other understudied species.

Novel Identification of Bacterial Epigenetic Regulations Would Benefit From a Better Exploitation of Methylomic Data

“…Furthermore, the deletion of m4C MTases encoding genes can impair virulence and cause broad transcriptional changes as shown in H. pylori (Kumar et al, 2012(Kumar et al, , 2018. In another human pathogen, Leptospira interrogans, the impaired virulence caused by the deletion of an MTase is associated to the dysregulation of an extracytoplasmic function (ECF) sigma factor (Gaultney et al, 2020).…”

Investigating the role of the carbon storage regulator A (CsrA) in Leptospira spp.

“…interrogans , we first overexpressed csrA of each strain under the control of the promoter of L . interrogans groES , which previously showed to be a strong promoter [ 53 ]. Consistent with the results observed in the complementation experiment, no colony was obtained for both L .…”

Experimental evolution of Vibrio cholerae: Identification of genes involved in motility in presence of polymyxin B

“…It is thus possible that the gain of motility observed in these variants is due to a transcriptional or an epigenetic regulation of gene expression. An increasing number of evidences suggest that epigenetic regulation through methylation is an important process for gene expression regulation, including antibiotic resistance and virulence [65, 66]. Regarding flagella, a methylation site has been reported in the flh operon in E. coli [67].…”