AUTHOR=Payelleville Amaury , Lanois Anne , Gislard Marie , Dubois Emeric , Roche David , Cruveiller Stéphane , Givaudan Alain , Brillard Julien 

TITLE=DNA Adenine Methyltransferase (Dam) Overexpression Impairs Photorhabdus luminescens Motility and Virulence

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.01671

DOI=10.3389/fmicb.2017.01671

ISSN=1664-302X

ABSTRACT=<p>Dam, the most described bacterial DNA-methyltransferase, is widespread in gamma-proteobacteria. Dam DNA methylation can play a role in various genes expression and is involved in pathogenicity of several bacterial species. The purpose of this study was to determine the role played by the <italic>dam</italic> ortholog identified in the entomopathogenic bacterium <italic>Photorhabdus luminescens</italic>. Complementation assays of an <italic>Escherichia coli dam</italic> mutant showed the restoration of the DNA methylation state of the parental strain. Overexpression of <italic>dam</italic> in <italic>P. luminescens</italic> did not impair growth ability <italic>in vitro</italic>. In contrast, compared to a control strain harboring an empty plasmid, a significant decrease in motility was observed in the <italic>dam</italic>-overexpressing strain. A transcriptome analysis revealed the differential expression of 208 genes between the two strains. In particular, the downregulation of flagellar genes was observed in the <italic>dam</italic>-overexpressing strain. In the closely related bacterium <italic>Xenorhabdus nematophila, dam</italic> overexpression also impaired motility. In addition, the <italic>dam</italic>-overexpressing <italic>P. luminescens</italic> strain showed a delayed virulence compared to that of the control strain after injection in larvae of the lepidopteran <italic>Spodoptera littoralis</italic>. These results reveal that Dam plays a major role during <italic>P. luminescens</italic> insect infection.</p>