Chawla, P.; Chen, Y.; Huynh, T. N.

Bacteriophages, particularly temperate prophages that integrate directly into the host genome, are crucial drivers of bacterial evolution and act as fundamental architects of microbial communities. Listeria monocytogenes 10403S has two phage elements, prophage {Phi}10403S and monocin element. In this study, we found that c-di-AMP, a crucial second messenger in L. monocytogenes, regulates phage production. C-di-AMP accumulation down-regulates the gene expression of prophage and monocin gene loci and inhibits phage production, both spontaneous phage production as well as under phage induction through mitomycin C treatment. We found that in genetically heterogenous cultures, super-infection of non-lysogenic strains with phage-containing strains can significantly amplify spontaneous prophage production. Using these cultures as an induction system, we found other inducers of spontaneous phage production. We found that ppGpp accumulation and nutrient starvation acts as an inducer of the spontaneous prophage production in L. monocytogenes. H2O2 can also play a role in inducing spontaneous phage production. Moreover, {Phi}10403S prophage production is suppressed in co-cultures of L. monocytogenes 10403S with L. monocytogenes F2365 and L. innocua CLIP11262.