CyranoPS, a novel compact temperate corynephage infecting Corynebacterium glutamicum MB001

Abstract

Here, we describe CyranoPS, a temperate phage isolated from the river Yvette in France, using the prophage-free strain Corynebacterium glutamicum MB001. Negative-stain electron microscopy revealed virions with siphovirus morphology. Its 14,910-bp genome has a GC content of 53.0% and 14-nt 3' overhangs at both ends. It carries 26 predicted genes, 10 without predicted functions, and no tRNAs. CyranoPS belongs to the newly established actinophage cluster ER, whose members have the smallest known genomes among Corynebacterium-infecting phages. Deletion of genes encoding the porin PorAH and the protein mycoloyltransferase MytC abolished infection, while genes encoding the mycomembrane proteins PorBC and ProtX were dispensable. CyranoPS established lysogeny in C. glutamicum through chromosomal integration probably mediated by its predicted tyrosine integrase. Integration truncated the immunity repressor gene Cyr_18, resulting in a protein devoid of its 15 C-terminal residues. The truncated repressor conferred stronger protection against superinfection than the full-length repressor. CyranoPS lysogens exhibited high levels of spontaneous prophage induction, reaching 109 PFU/mL under standard conditions, with no further increase upon treatment with mitomycin C. These findings suggest a potentially SOS-independent lytic-lysogenic switch and establish CyranoPS as a compact model to study infection and lysogeny regulation in Mycobacteriales.