Every multicellular organism is associated with a complex microbiota, whose interactions are important for maintenance of physiological homeostasis. In order to investigate these interactions, we isolated a bacteriophage we intended to utilize to manipulate the host-associated microbial community of Hydra vulgaris AEP. During this process we tested the phage's ability to infect and eliminate Curvibacter sp. AEP1.3 in liquid culture, on solid medium and in association with Hydra and found that infectivity varied. To further our understanding of these bacterial states, we compared them via RNA Sequencing and found that they differed significantly in their expression patterns. These findings indicated that Curvibacter transitioned between three different lifestyles, which resulted in varying degrees of susceptibility to bacteriophage infection. This concept could be relevant both for microbiota research and phage therapy.